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Background: Patients with chronic kidney disease often have increased plasma cardiac troponin concentration in the absence of myocardial infarction. Incidence of myocardial infarction is high in this population, and diagnosis, particularly of non ST-segment elevation myocardial infarction (NSTEMI), is challenging. Knowledge of biological variation aids understanding of serial cardiac troponin measurements and could improve interpretation in clinical practice. The National Academy of Clinical Biochemistry (NACB) recommended the use of a 20% reference change value in patients with kidney failure. The aim of this study was to calculate the biological variation of cardiac troponin I and cardiac troponin T in patients with moderate chronic kidney disease (glomerular filtration rate [GFR] 30–59 mL/min/1.73 m2). Methods and results: Plasma samples were obtained from 20 patients (median GFR 43.0 mL/min/1.73 m2) once a week for four consecutive weeks. Cardiac troponin I (Abbott ARCHITECT® i2000SR, median 4.3 ng/L, upper 99th percentile of reference population 26.2 ng/L) and cardiac troponin T (Roche Cobas® e601, median 11.8 ng/L, upper 99th percentile of reference population 14 ng/L) were measured in duplicate using high-sensitivity assays. After outlier removal and log transformation, 18 patients' data were subject to ANOVA, and within-subject (CVI), between-subject (CVG) and analytical (CVA) variation calculated. Variation for cardiac troponin I was 15.0%, 105.6%, 8.3%, respectively, and for cardiac troponin T 7.4%, 78.4%, 3.1%, respectively. Reference change values for increasing and decreasing troponin concentrations were +60%/–38% for cardiac troponin I and +25%/–20% for cardiac troponin T. Conclusions: The observed reference change value for cardiac troponin T is broadly compatible with the NACB recommendation, but for cardiac troponin I, larger changes are required to define significant change. The incorporation of separate RCVs for cardiac troponin I and cardiac troponin T, and separate RCVs for rising and falling concentrations of cardiac troponin, should be considered when developing guidance for interpretation of sequential cardiac troponin measurements. [ABSTRACT FROM AUTHOR]

Objectives: To perform a cross-sectional comparison of endogenous markers of glomerular filtration rate (GFR) (plasma symmetric dimethylarginine (SDMA) and estimated GFR (eGFR)) with a direct measure of GFR (using the plasma clearance of Inutest (In-GFR)), and a longitudinal evaluation of these markers in relation to the development of microalbuminuria, in young people with type 1 diabetes (T1D).Methods: Longitudinal stored blood samples (n=1105) were available from 417 young people from the Oxford Regional Prospective Study (an inception cohort of 527 children followed for a median of 10.3 (interquartile range 7.1-12.3) years), for measurement of SDMA and creatinine. Additional annually collected data on anthropometric parameters, HbA1c, insulin dose and three early morning albumin:creatinine ratios were available. In-GFR was measured in a representative subgroup of 183 subjects.Main Outcome Measures: SDMA and eGFR.Results: SDMA and eGFR were significantly and similarly associated with In-GFR (r=-0.38 and r=0.36, p<0.001). Overall SDMA levels were lower in microalbuminuric (n=116) than normoalbuminuric subjects (n=301) (0.385 + or - 0.063 vs 0.412 + or - 0.059 micromol/l, p<0.001), probably reflecting hyperfiltration. The pattern of change in SDMA levels with age differed between microalbuminuric and normoalbuminuric subjects. Whereas SDMA levels declined in both groups until the age of 16 years, thereafter they tended to rise only in microalbuminuric subjects, probably reflecting a decline in renal function.Conclusions: In this longitudinal study of young people with T1D, measurement of SDMA, in contrast to eGFR, proved to be a reliable marker in identifying changes in filtration rates associated with the development of microalbuminuria (MA). [ABSTRACT FROM AUTHOR]

Objectives It has been suggested that homozygous c.985A>G medium-chain acyl-CoA dehydrogenase deficiency (MCADD) is a disease of White ethnic origin but little is known regarding its ethnic distribution. We estimated ethnic-specific homozygous c.985A>G MCADD birth prevalence from a large-scale UK newborn screening study.Methods Homozygous c.985A>G MCADD cases were ascertained in six English newborn screening centres between 1 March 2004 and 28 February 2007 by screening approximately 1.1 million newborns using tandem mass spectrometry analysis of underivatised blood spot samples to quantitate octanoylcarnitine (C8). Follow-up biochemistry and mutation analyses for cases (mean triplicate C8 value >/= 0.5 µmol/L) were reviewed to confirm diagnosis. Ethnicity was ascertained from clinician report and denominators from 2001 UK Census estimates of ethnic group of children less than one year.Results Sixty-four infants were c.985A>G MCADD homozygotes (overall prevalence 5.8 per 100,000 live births; 95% CI 4.4DS7.2). Sixty (93%) were White, two (3%) were mixed/other and two were of unknown ethnic origin. No Asian or Black homozygotes were identified. Proportions of White, mixed/other, Asian and Black births in screening regions were estimated, yielding homozygous c.985A>G MCADD birth prevalence of 6.9 per 100,000 (95% CI 5.2DS8.8) in White, and 95% CI estimates of 0DS2.7 per 100,000 in Asian and 0DS5.8 in Black populations. The c.985A>G carrier frequency in the White group was estimated at one in 65 (95% CI 1/74, 1/61) under HardyDSWeinberg conditions.Conclusion c.985A>G homozygous MCADD is not found in Black and Asian ethnic groups that have been screened at birth in England. This is consistent with the earlier published observations suggesting that MCADD due to the c.985A>G mutation is a disease of White ethnic origin. [ABSTRACT FROM AUTHOR]

BACKGROUND: Fenofibrate was associated with increases in serum creatinine concentrations. The effect of short-term fenofibrate treatment on kidney function was investigated in subjects with normal kidney function. STUDY DESIGN: Double-blind, crossover, placebo-controlled. SETTING AND PARTICIPANTS: 24 middle-aged subjects with normal kidney function (estimated creatinine clearance > or = 80 mL/min). INTERVENTION: Subjects were treated with fenofibrate (160-mg/d tablet) and placebo in two 6-week periods separated by a washout. OUTCOMES AND MEASUREMENTS: The primary outcome measure was glomerular filtration rate measured by means of inulin clearance, with a test of noninferiority to rule out a change in the 95% confidence interval (CI) greater than 20%. Secondary outcomes included effective renal plasma flow measured by means of para-aminohippurate (PAH) clearance, creatinine clearance, creatinine secretion (ratio of creatinine to inulin clearance), serum cystatin C and uric acid, and urinary excretion of creatinine. Glomerular and tubular damage was evaluated by using albumin and retinol-binding protein levels and N-acetyl-beta-d-glucosaminidase activity. RESULTS: Inulin clearance was unchanged after fenofibrate (change [Delta] between treatments on 6-week values, 0.8 mL/min; 95% CI, -10.5 to 12.2; P = 0.9), but PAH clearance decreased (Delta, -33; 95% CI, -66 to -1; P = 0.05). Changes in inulin and PAH clearances were not greater than 20%. Plasma creatinine level increased (Delta, 0.11 mg/dL; 95% CI, 0.05 to 0.18; P < 0.05), and creatinine clearance decreased (Delta, -9.5 mL/min; 95% CI, -14.4 to -4.7; P < 0.001). Creatinine secretion and urinary creatinine excretion were unchanged (Delta, -0.05; 95% CI, -0.11 to 0.02; P = 0.2; Delta, 0.37 g/24 h; 95% CI, -0.13 to 0.88; P = 0.1, respectively). Plasma cystatin C level increased (Delta, 0.18 mg/L; 95% CI, 0.03 to 0.34; P = 0.02) and serum uric acid level decreased (Delta, -0.7 mg/dL; 95% CI, -1.2 to -0.3; P = 0.1). Urinary albumin and retinol-binding protein levels were unchanged, but urinary N-acetyl-beta-d-glucosaminidase activity increased (Delta, 20.0 mumol/h/mmol creatinine; 95% CI, 9.3 to 30.7; P = 0.001). LIMITATIONS: Short treatment duration and inclusion of healthy subjects precludes conclusions about effects of longer term use in patients with kidney disease. Small changes in glomerular filtration rate may be difficult to detect by using clearance methods. Interference with the creatinine assay cannot be excluded. CONCLUSION: Short-term fenofibrate treatment did not alter glomerular filtration rate by more than 20% in subjects with normal kidney function, but a smaller decrease cannot be ruled out. Increased serum creatinine levels may be caused by decreased creatinine clearance. The explanation for decreased creatinine clearance and increased serum creatinine levels in this study is not clear. Copyright © 2008 National Kidney Foundation, Inc. [ABSTRACT FROM AUTHOR]

Objective: To describe longitudinal variations in pubertal hormonal variables in subjects with and without microalbuminuria (MA).Research Design and Methods: Blood samples collected annually from subjects recruited at diagnosis of type 1 diabetes and followed prospectively through puberty (median follow-up 9.3 years, range 4.7-12.8) were analyzed for total and free IGF-I, IGF binding protein-1, testosterone, sex hormone-binding globulin, and HbA(1c). A total of 55 subjects who developed MA (MA(+) group) were compared with 55 age-, sex-, and duration-matched control subjects who did not develop MA (MA(-) group).Results: For female subjects, total IGF-I (MA(+) 1.2 mU/l vs. MA(-) 1.4 mU/l, P = 0.03) and free IGF-I levels (MA(+) 1,767 ng/l vs. MA(-) 2010 ng/l, P = 0.002) were lower, whereas the free androgen index (MA(+) 2.4 vs. MA(-) 2.0, P = 0.03) was higher in those with MA. These changes were less pronounced in male subjects. For both sexes, in a Cox model after adjusting for puberty, the presence of MA was associated with lower free IGF-I levels, higher testosterone standard deviation score (SDS), and poor glycemic control. We found that 22 of 55 case subjects (40%) developed persistent MA, whereas 33 (60%) had transient MA. In the persistent MA group compared with the transient and control groups, total IGF-I levels were lower (1.1 vs. 1.3 vs. 1.4 mU/l, P = 0.002) as were free IGF-I levels (1,370.9 vs. 1,907.3 vs. 1,886.7 ng/l, P < 0.001), whereas HbA(1c) levels were higher (11.8 vs. 10.3 vs. 9.9%, P < 0.001).Conclusions: Poor glycemic control and differences in IGF-I levels and androgens, particularly in female subjects, accompany development of MA at puberty. These differences may in part account for the sexual dimorphism in MA risk during puberty and could relate to disease progression. [ABSTRACT FROM AUTHOR]

OBJECTIVES: To perform a longitudinal evaluation of high-sensitivity C-reactive protein (hs-CRP) in young people with type 1 diabetes in relation to the development of microalbuminuria (MA). RESEARCH DESIGN AND METHODS: hs-CRP was measured in 329 blood samples collected from 49 subjects with type 1 diabetes with MA and 49 normoalbuminuric subjects matched for age, sex, and duration of diabetes. RESULTS: In subjects developing MA, a progressive rise in hs-CRP was detected with levels significantly higher in the years after the onset of MA when compared with levels before MA onset (P = 0.003; age-adjusted P = 0.06). After the onset of MA, hs-CRP levels were significantly higher in subjects with MA when compared with normoalbuminuric subjects (median 1.9 mg/l [range 0.2-9.8] vs. 1.1 mg/l [0.2-6.4]; P = 0.02; adjusted P = 0.036). CONCLUSIONS: In this population of young subjects with type 1 diabetes, there was a significant increase in hs-CRP levels after the onset of MA, likely reflecting a general state of inflammation. [ABSTRACT FROM AUTHOR]

Ketonuria accompanying hypoglycaemia is conventionally thought to exclude fat oxidation defects. We describe a 2 year old girl with hypoglycaemic encephalopathy in whom a diagnosis of very long chain acyl CoA dehydrogenase deficiency was suggested on the basis of acylcarnitine analysis despite massive ketonuria. [ABSTRACT FROM AUTHOR]

Objectives: To examine the relationship between kidney hyperfiltration during adolescence and subsequent changes in estimated glomerular filtration rate (eGFR) and urinary albumin creatinine ratio (UACR) in a young cohort of participants with type 1 diabetes. Additionally, to explore urinary mitochondrial DNA:nuclear DNA ratio (mtDNA:nDNA) as a marker of metabolic stress and its association with early changes in kidney function., Methods: Eighty adolescents were studied at baseline [mean (SD) age 14.2 (1.5) years; mean diabetes duration 6.7 (3.0) years] and followed up 9.2 (1.3) years later. Blood pressure, HbA1c, lipids, eGFR, UACR and heart rate variability were assessed at each visit. Urinary mtDNA:nDNA was measured by quantitative PCR (qPCR)., Results: Overall, 4.2% of participants had diabetic kidney disease (DKD) at follow-up. Hyperfiltration at baseline (>135 mL/min/1.73m2) was seen in 31% of adolescents and was associated with a decline in eGFR at follow-up when adjusted for sex, diabetes duration and HbA1c [hyperfiltration -1.46 (3.07) mL/min/1.73 m2/year vs non-hyperfiltration -0.51 (2.48) mL/min/1.73m2/year, P=0.02]. Participants with hyperfiltration also had higher odds of undergoing rapid eGFR decline (>3 mL/min/1.73m2/year) compared to those without hyperfiltration [OR 14.11, 95% CI (2.30-86.60), P=0.004]. Baseline urinary mtDNA:nDNA was significantly associated with both greater annual rate of eGFR decline and rapid eGFR decline in univariable but not multivariable modelling., Conclusion: Hyperfiltration during adolescence is significantly associated with greater reduction in eGFR and higher risk of rapid eGFR decline after ∼9 years, following transition into young adulthood in type 1 diabetes. Urinary mtDNA:nDNA measured during adolescence may be a novel predictor of early changes in kidney function., (© The Author(s) 2024. Published by Oxford University Press on behalf of the Endocrine Society. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com. See the journal About page for additional terms.)

In clinical practice, the glomerular filtration rate (GFR), a measurement of kidney functioning, is normally calculated using equations, such as the European Kidney Function Consortium (EKFC) equation. Despite being the most general equation, EKFC, just like previously proposed approaches, can still struggle to achieve satisfactory performance, limiting its clinical applicability. As a possible solution, recently machine learning (ML) has been investigated to improve GFR prediction, nonetheless the literature still lacks a general and multi-center study. Using a dataset with 19,629 patients from 13 cohorts, we investigate if ML can improve GFR prediction in comparison to EKFC. More specifically, we compare diverse ML methods, which were allowed to use age, sex, serum creatinine, cystatin C, height, weight and BMI as features, in internal and external cohorts against EKFC. The results show that the most performing ML method, random forest (RF), and EKFC are very competitive where RF and EKFC achieved respectively P10 and P30 values of 0.45 (95% CI 0.44;0.46) and 0.89 (95% CI 0.88;0.90), whereas EKFC yielded 0.44 (95% CI 0.43; 0.44) and 0.89 (95% CI 0.88; 0.90), considering the entire cohort. Small differences were, however, observed in patients younger than 12 years where RF slightly outperformed EKFC., (© 2024. The Author(s).)

International consensus supports the development of standardized protocols for measured glomerular filtration rate (mGFR) to facilitate the integration of mGFR testing in both clinical and research settings. To this end, the European Kidney Function Consortium convened an international group of experts with relevant experience in mGFR. The working group performed an extensive literature search to inform the development of recommendations for mGFR determination using 1-compartment plasma clearance models and iohexol as the exogenous filtration marker. Iohexol was selected as it is non-radio labeled, inexpensive, and safe, can be assayed at a central laboratory, and the other commonly used non-radio-labeled tracers have been (inulin) or are soon to be (iothalamate) discontinued. A plasma clearance model was selected over urine clearance as it requires no urine collection. A 1 compartment was preferred to 2 compartments as it requires fewer samples. The recommendations are based on published evidence complemented by expert opinion. The consensus paper covers practical advice for patients and health professionals, preparation, administration, and safety aspects of iohexol, laboratory analysis, blood sample collection and sampling times using both multiple and single-sample protocols, description of the mGFR mathematical calculations, as well as implementation strategies. Supplementary materials include patient and provider information sheets, standard operating procedures, a study protocol template, and support for mGFR calculation., (Copyright © 2024 International Society of Nephrology. Published by Elsevier Inc. All rights reserved.)

Background: Estimation of glomerular filtration rate using equations based on creatinine is widely used to manage chronic kidney disease. In the UK, the Chronic Kidney Disease Epidemiology Collaboration creatinine equation is recommended. Other published equations using cystatin C, an alternative marker of kidney function, have not gained widespread clinical acceptance. Given higher cost of cystatin C, its clinical utility should be validated before widespread introduction into the NHS., Objectives: Primary objectives were to: (1) compare accuracy of glomerular filtration rate equations at baseline and longitudinally in people with stage 3 chronic kidney disease, and test whether accuracy is affected by ethnicity, diabetes, albuminuria and other characteristics; (2) establish the reference change value for significant glomerular filtration rate changes; (3) model disease progression; and (4) explore comparative cost-effectiveness of kidney disease monitoring strategies., Design: A longitudinal, prospective study was designed to: (1) assess accuracy of glomerular filtration rate equations at baseline ( n  = 1167) and their ability to detect change over 3 years ( n  = 875); (2) model disease progression predictors in 278 individuals who received additional measurements; (3) quantify glomerular filtration rate variability components ( n  = 20); and (4) develop a measurement model analysis to compare different monitoring strategy costs ( n  = 875)., Setting: Primary, secondary and tertiary care., Participants: Adults (≥ 18 years) with stage 3 chronic kidney disease., Interventions: Estimated glomerular filtration rate using the Chronic Kidney Disease Epidemiology Collaboration and Modification of Diet in Renal Disease equations., Main Outcome Measures: Measured glomerular filtration rate was the reference against which estimating equations were compared with accuracy being expressed as P30 (percentage of values within 30% of reference) and progression (variously defined) studied as sensitivity/specificity. A regression model of disease progression was developed and differences for risk factors estimated. Biological variation components were measured and the reference change value calculated. Comparative costs of monitoring with different estimating equations modelled over 10 years were calculated., Results: Accuracy (P30) of all equations was ≥ 89.5%: the combined creatinine-cystatin equation (94.9%) was superior ( p  < 0.001) to other equations. Within each equation, no differences in P30 were seen across categories of age, gender, diabetes, albuminuria, body mass index, kidney function level and ethnicity. All equations showed poor (< 63%) sensitivity for detecting patients showing kidney function decline crossing clinically significant thresholds (e.g. a 25% decline in function). Consequently, the additional cost of monitoring kidney function annually using a cystatin C-based equation could not be justified (incremental cost per patient over 10 years = £43.32). Modelling data showed association between higher albuminuria and faster decline in measured and creatinine-estimated glomerular filtration rate. Reference change values for measured glomerular filtration rate (%, positive/negative) were 21.5/-17.7, with lower reference change values for estimated glomerular filtration rate., Limitations: Recruitment of people from South Asian and African-Caribbean backgrounds was below the study target., Future Work: Prospective studies of the value of cystatin C as a risk marker in chronic kidney disease should be undertaken., Conclusions: Inclusion of cystatin C in glomerular filtration rate-estimating equations marginally improved accuracy but not detection of disease progression. Our data do not support cystatin C use for monitoring of glomerular filtration rate in stage 3 chronic kidney disease., Trial Registration: This trial is registered as ISRCTN42955626., Funding: This award was funded by the National Institute for Health and Care Research (NIHR) Health Technology Assessment programme (NIHR award ref: 11/103/01) and is published in full in Health Technology Assessment ; Vol. 28, No. 35. See the NIHR Funding and Awards website for further award information.

Glycogen storage disease type Ib (GSD Ib, biallelic variants in SLC37A4) is a rare disorder of glycogen metabolism complicated by neutropenia/neutrophil dysfunction. Since 2019, the SGLT2-inhibitor empagliflozin has provided a mechanism-based treatment option for the symptoms caused by neutropenia/neutrophil dysfunction (e.g. mucosal lesions, inflammatory bowel disease). Because of the rarity of GSD Ib, the published evidence on safety and efficacy of empagliflozin is still limited and does not allow to develop evidence-based guidelines. Here, an international group of experts provides 14 best practice consensus treatment recommendations based on expert practice and review of the published evidence. We recommend to start empagliflozin in all GSD Ib individuals with clinical or laboratory signs related to neutropenia/neutrophil dysfunction with a dose of 0.3-0.4 mg/kg/d given as a single dose in the morning. Treatment can be started in an outpatient setting. The dose should be adapted to the weight and in case of inadequate clinical treatment response or side effects. We strongly recommend to pause empagliflozin immediately in case of threatening dehydration and before planned longer surgeries. Discontinuation of G-CSF therapy should be attempted in all individuals. If available, 1,5-AG should be monitored. Individuals who have previously not tolerated starches should be encouraged to make a new attempt to introduce starch in their diet after initiation of empagliflozin treatment. We advise to monitor certain safety and efficacy parameters and recommend continuous, alternatively frequent glucose measurements during the introduction of empagliflozin. We provide specific recommendations for special circumstances like pregnancy and liver transplantation., Competing Interests: Declaration of competing interest All authors with exception of ELC, JlF, PH and SKU received accommodation support by Sophie's Hope Foundation. All authors report no conflict of interest related to this study. TGJD declares that he has confidentiality agreements with third parties. In the past 36 months, there have been consultation agreements (with Danone, Ultragenyx Pharmaceutical Inc, ModernaTX Inc., and Beam Therapeutics), contracts for financial research support for investigator-initiated research (NCT04311307) and sponsor-initiated research (NCT03517085, NCT03970278, NCT05139316, and NCT05196165), honoraria for lectures or presentations (by MEDTalks, Prelum, and Danone), and participations in a Data Safety Monitoring Board (NCT05095727) and Advisory Boards (Ultragenyx Pharmaceutical Inc, ModernaTX Inc., and Beam Therapeutics). For all private-public relationships, all contracts are via UMCG Contract Research Desk and all payments are to UMCG. ND declares that he is a director and minority shareholder in SpOtOn Clinical Diagnostics Ltd. KMS declares that in the last 36 months there were consultancy agreements with BioMarin, Chiesi, Takeda, Sanofi, Amicus and Immusoft Corporation. SCG declares that over the last 3 years in the area of inherited metabolic diseases she has received accommodation support from Nutricia Metabolics, honoraria for lectures from Vitaflo and Ultragenyx, and that she is an advisory board member of Ultragenyx. JL and BS declare no conflict of interest. Funding to Sophie's Hope Foundation and curegsd1b.org is by individual donors, rather than pharmaceutical or medical food industry. ELC declares no conflict of interest. C.D. Nina la Guerrera (www.ninalaguerrera.org) is a small size non-for-profit platform, whose main sources of funding are by individual donors from sectors that have no interest in biomedical research. HM declares that over the last 3 years in the area of inherited metabolic diseases she has received accommodation support from Vitaflo. honoraria for lectures from Vitaflo and Nutricia and served as a paid consultant for Ultragenyx. SBW declares that over the last 3 years in the area of inherited metabolic diseases she has received accommodation support from Nutricia Metabolics., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Background: Given limited data regarding the involvement of disadvantaged groups in paediatric diabetes clinical trials, this study aimed to evaluate the socioeconomic representativeness of participants recruited into a multinational clinical trial in relation to regional and national type 1 diabetes reference populations., Methods: Retrospective, cross-sectional evaluation of a subset of adolescent type 1 diabetes cardiorenal intervention trial (AdDIT) participants from Australia (n = 144), Canada (n = 312) and the UK (n = 173). Validated national measures of deprivation were used: the Index of Relative Socioeconomic Disadvantage (IRSD) 2016 (Australia), the Material Resources (MR) dimension of the Canadian Marginalisation index 2016 (Canada) and the Index of Multiple Deprivation (IMD) 2015 (UK). Representativeness was assessed by comparing the AdDIT cohort's distribution of deprivation quintiles with that of the local paediatric type 1 diabetes population (regional), and the broader type 1 diabetes population for which the trial's intervention was targeted (national)., Results: Recruited study cohorts from each country had higher proportions of participants with higher SES, and significant underrepresentation of lower SES, in relation to their national references. The socioeconomic make-up in Australia mirrored that of the regional population (p = 0.99). For Canada, the 2nd least deprived (p = 0.001) and the most deprived quintiles (p < 0.001) were over- and under-represented relative to the regional reference, while the UK featured higher regional and national SES bias with over-representation and under-representation from the least-deprived and most-deprived quintiles (p < 0.0001)., Conclusions: Significant national differences in trial participation of low SES participants were observed, highlighting limitations in access to clinical research and the importance of reporting sociodemographic representation in diabetes clinical trials., Trial Registration: NCT01581476. Registered on 20 April 2012., (© 2023. The Author(s).)

Background: A new Chronic Kidney Disease Epidemiology Collaboration equation without the race variable has been recently proposed (CKD-EPIAS). This equation has neither been validated outside USA nor compared with the new European Kidney Function Consortium (EKFC) and Lund-Malmö Revised (LMREV) equations, developed in European cohorts., Methods: Standardized creatinine and measured glomerular filtration rate (GFR) from the European EKFC cohorts (n = 13 856 including 6031 individuals in the external validation cohort), from France (n = 4429, including 964 Black Europeans), from Brazil (n = 100) and from Africa (n = 508) were used to test the performances of the equations. A matched analysis between White Europeans and Black Africans or Black Europeans was performed., Results: In White Europeans (n = 9496), both the EKFC and LMREV equations outperformed CKD-EPIAS (bias of -0.6 and -3.2, respectively versus 5.0 mL/min/1.73 m², and accuracy within 30% of 86.9 and 87.4, respectively, versus 80.9%). In Black Europeans and Black Africans, the best performance was observed with the EKFC equation using a specific Q-value (= concentration of serum creatinine in healthy males and females). These results were confirmed in matched analyses, which showed that serum creatinine concentrations were different in White Europeans, Black Europeans and Black Africans for the same measured GFR, age, sex and body mass index. Creatinine differences were more relevant in males., Conclusion: In a European and African cohort, the performances of CKD-EPIAS remain suboptimal. The EKFC equation, using usual or dedicated population-specific Q-values, presents the best performance in the whole age range in the European and African populations included in this study., (© The Author(s) 2022. Published by Oxford University Press on behalf of the ERA.)

Objectives: During 2020, the UK's Department of Health and Social Care (DHSC) established the Moonshot programme to fund various diagnostic approaches for the detection of SARS-CoV-2, the pathogen behind the COVID-19 pandemic. Mass spectrometry was one of the technologies proposed to increase testing capacity., Methods: Moonshot funded a multi-phase development programme, bringing together experts from academia, industry and the NHS to develop a state-of-the-art targeted protein assay utilising enrichment and liquid chromatography tandem mass spectrometry (LC-MS/MS) to capture and detect low levels of tryptic peptides derived from SARS-CoV-2 virus. The assay relies on detection of target peptides, ADETQALPQRK (ADE) and AYNVTQAFGR (AYN), derived from the nucleocapsid protein of SARS-CoV-2, measurement of which allowed the specific, sensitive, and robust detection of the virus from nasopharyngeal (NP) swabs. The diagnostic sensitivity and specificity of LC-MS/MS was compared with reverse transcription quantitative real-time polymerase chain reaction (RT-qPCR) via a prospective study., Results: Analysis of NP swabs (n=361) with a median RT-qPCR quantification cycle (Cq) of 27 (range 16.7-39.1) demonstrated diagnostic sensitivity of 92.4% (87.4-95.5), specificity of 97.4% (94.0-98.9) and near total concordance with RT-qPCR (Cohen's Kappa 0.90). Excluding Cq>32 samples, sensitivity was 97.9% (94.1-99.3), specificity 97.4% (94.0-98.9) and Cohen's Kappa 0.95., Conclusions: This unique collaboration between academia, industry and the NHS enabled development, translation, and validation of a SARS-CoV-2 method in NP swabs to be achieved in 5 months. This pilot provides a model and pipeline for future accelerated development and implementation of LC-MS/MS protein/peptide assays into the routine clinical laboratory., (© 2022 Walter de Gruyter GmbH, Berlin/Boston.)

Background: Glycogen storage disease type Ib (GSD Ib) is a severe disorder of carbohydrate metabolism due to bi-allelic variants in SLC37A4. It is associated with neutropaenia and neutrophil dysfunction, which has recently been attributed to the accumulation of 1,5-anhydroglucitol-6-phosphate (1,5AG6P) within neutrophils. Treatment with sodium-glucose co-transporter-2 (SGLT2) inhibitors, such as empagliflozin, is a novel therapy that reduces 1,5-anhydroglucitol (1,5AG) in plasma., Results: We report our experience in treating 8 paediatric GSD Ib patients with empagliflozin with a cumulative treatment time greater than 12 years. Treatment with a median dose of 5 mg (0.22 mg/kg height weight) of empagliflozin resulted in improvement in bowel health, growth, and laboratory parameters. Plasma 1,5AG levels reduced by a median of 78%. Baseline 1,5AG levels in our cohort were higher than in adult patients with GSD Ib. Hypoglycaemia on empagliflozin treatment occurred in 50% of our cohort., Conclusion: We report the largest single centre cohort of GSD Ib patients treated with empagliflozin to date. Treatment with SGLT2 inhibitors is a novel and favourable treatment option for neutropaenia and neutrophil dysfunction in GSD Ib. We suggest a low starting dose of empagliflozin with careful titration due to the risk of hypoglycaemia. The interpretation of 1,5AG levels and their role in treatment monitoring is yet to be established, and requires ongoing research., (© 2022. The Author(s).)

Aims/hypothesis: We hypothesised that adolescents with type 1 diabetes with a urinary albumin/creatinine ratio (ACR) in the upper tertile of the normal range (high ACR) are at greater risk of three-step diabetic retinopathy progression (3DR) independent of glycaemic control., Methods: This was a prospective observational study in 710 normoalbuminuric adolescents with type 1 diabetes from the non-intervention cohorts of the Adolescent Cardio-Renal Intervention Trial (AdDIT). Participants were classified as 'high ACR' or 'low ACR' (lowest and middle ACR tertiles) using baseline standardised log 10 ACR. The primary outcome, 3DR, was determined from centrally graded, standardised two-field retinal photographs. 3DR risk was determined using multivariable Cox regression for the effect of high ACR, with HbA 1c , BP, LDL-cholesterol and BMI as covariates; diabetes duration was the time-dependent variable., Results: At baseline mean ± SD age was 14.3 ± 1.6 years and mean ± SD diabetes duration was 7.2 ± 3.3 years. After a median of 3.2 years, 83/710 (12%) had developed 3DR. In multivariable analysis, high ACR (HR 2.1 [1.3, 3.3], p=0.001), higher mean IFCC HbA 1c (HR 1.03 [1.01, 1.04], p=0.001) and higher baseline diastolic BP SD score (HR 1.43 [1.08, 1.89], p=0.01) were independently associated with 3DR risk., Conclusions/interpretation: High ACR is associated with greater risk of 3DR in adolescents, providing a target for future intervention studies., Trial Registration: isrctn.org ISRCTN91419926., (© 2022. The Author(s).)

Aim: The Cockcroft-Gault (CG) creatinine-based equation is still used to estimate glomerular filtration rate (eGFR) for drug dosage adjustment. Incorrect eGFR may lead to hazardous over- or underdosing., Methods: In a cross-sectional analysis, CG was validated against measured GFR (mGFR) in 14 804 participants and compared with the Modification-of-Diet-in-Renal-Diseases (MDRD), Chronic-Kidney-Disease-Epidemiology (CKD-EPI), Lund-Malmö-Revised (LMR) and European-Kidney-Function-Consortium (EKFC) equations. Validation focused on bias, imprecision and accuracy (percentage of estimates within ±30% of mGFR, P30), overall and stratified for mGFR, age and body mass index at mGFR <60 mL/min, as well as classification in mGFR stages., Results: The CG equation performed worse than the other equations, overall and in mGFR, age and BMI subgroups in terms of bias (systematic overestimation), imprecision and accuracy except for patients ≥65 years where bias and P30 were similar to MDRD and CKD-EPI, but worse than LMR and EKFC. In subjects with mGFR <60 mL/min and at BMI 18.5-25 kg/m 2 , all equations performed similarly, and for BMI < 18.5 kg/m 2 CG and LMR had the best results though all equations had poor P30-accuracy. At BMI ≥ 25 kg/m 2 the bias of the CG increased with increasing BMI (+17.2 mL/min at BMI ≥ 40 kg/m 2 ). The four more recent equations also classified mGFR stages better than CG., Conclusions: The CG equation showed poor ability to estimate GFR overall and in analyses stratified for mGFR, age and BMI. CG was inferior to correctly classify the patients in the mGFR staging compared to more recent creatinine-based equations., (© 2021 British Pharmacological Society.)

Early detection of CKD using point of care creatinine and eGFR testing improves patient management outcomes. We undertook a field study to evaluate the use of a whole blood creatinine/eGFR device to screen a rural Nicaraguan population to determine the variability between creatinine methods and specimen types. All specimens including capillary and venous dried blood spots (DBS) were tested with an isotope dilution liquid chromatography mass spectrometry (ID-LCMS) gold standard method. This is to our knowledge the first time a capillary whole blood (POC) method has been directly compared to the gold standard IDMS method, through the novel approach of using dried blood spots. Capillary and venous whole blood specimens were obtained and tested directly with the BCMS method, and then, DBS samples were prepared. Venous plasma specimens were tested using three laboratory analyzer creatinine methods. DBS were sent to the site performing ID-LCMS. Control samples were also prepared to assess the stability of shipment and storage of DBS. The ID-LCMS method was aligned using primary and secondary standards. Sixty-six (66) patients participated in the study, and the CKD prevalence rate was 7.8%. While all creatinine methods showed a good correlation to ID-LCMS, there was a positive bias (mean absolute bias range: 0.21-0.63 mg/dL). All methods used were 100% sensitive, but specificity varied from 62.7 to 94.9% with PPV ranging from 25 to 62.5%. A correction factor was used to align the values from each method to ID-LCMS which improved the specificity of each method. This study used a unique DBS approach to align capillary whole blood creatinine to ID-LCMS. To ensure reliability of BCMS for identifying screened patients with CKD, it is important to establish IDMS traceability and alignment prior to undertaking CKD studies., (© 2022. The Author(s).)

Prospective biomarker studies can be used to identify biomarkers predictive of disease onset. However, if serum biomarkers are measured years after their collection, the storage conditions might affect analyte concentrations. Few data exists concerning which metabolites and proteins are affected by storage at - 20 °C vs - 80 °C. Our objectives were to document analytes affected by storage of serum samples at - 20 °C vs - 80 °C, and to identify those indicative of the storage temperature. We utilized liquid chromatography tandem mass spectrometry and Luminex to quantify 300 analytes from serum samples of 16 Finnish individuals with type 1 diabetes, with split-aliquot samples stored at - 80 °C and - 20 °C for a median of 4.2 years. Results were validated in 315 Finnish and 916 Scottish individuals with type 1 diabetes, stored at - 20 °C and at - 80 °C, respectively. After quality control, we analysed 193 metabolites and proteins of which 120 were apparently unaffected and 15 clearly susceptible to storage at - 20 °C vs - 80 °C. Further, we identified serum glutamate/glutamine ratio greater than 0.20 as a biomarker of storage at - 20 °C vs - 80 °C. The results provide a catalogue of analytes unaffected and affected by storage at - 20 °C vs - 80 °C and biomarkers indicative of sub-optimal storage., (© 2022. The Author(s).)

Background: Iohexol plasma clearance-based glomerular filtration rate (GFR) determination provides an accurate method for renal function evaluation. This technique is increasingly advocated for clinical situations that dictate highly accurate renal function assessment, as an alternative to conventional serum creatinine-based methods with limited accuracy or poor feasibility. In the renal transplantation setting, this particularly applies to living renal transplant donor eligibility screening, renal transplant function monitoring and research purposes. The dependency of current iohexol GFR estimation techniques on extensive sampling, however, has limited its clinical application. We developed a population pharmacokinetic model and limited sampling schedules, implemented in the online InsightRX precision dosing platform, to facilitate pragmatic iohexol GFR assessment., Methods: Iohexol concentrations (n = 587) drawn 5 min to 4 h after administration were available from 67 renal transplant recipients and 41 living renal transplant donor candidates with measured iohexol GFRs of 27-117 mL/min/1.73 m 2 . These were split into a model development (n = 72) cohort and an internal validation (n = 36) cohort. External validation was performed with 1040 iohexol concentrations from 268 renal transplant recipients drawn between 5 min and 4 h after administration, and extended iohexol curves up to 24 h from 11 random patients with impaired renal function. Limited sampling schedules based on one to four blood draws within 4 h after iohexol administration were evaluated in terms of bias and imprecision, using the mean relative prediction error and mean absolute relative prediction error. The total deviation index and percentage of limited sampling schedule-based GFR predictions within ± 10% of those of the full model (P 10 ) were assessed to aid interpretation., Results: Iohexol pharmacokinetics was best described with a two-compartmental first-order elimination model, allometrically scaled to fat-free mass, with patient type as a covariate on clearance and the central distribution volume. Model validity was confirmed during the internal and external validation. Various limited sampling schedules based on three to four blood draws within 4 h showed excellent predictive performance (mean relative prediction error < ± 0.5%, mean absolute relative prediction error < 3.5%, total deviation index < 5.5%, P 10 > 97%). The best limited sampling schedules based on three to four blood draws within 3 h showed reduced predictive performance (mean relative prediction error < ± 0.75%, mean absolute relative prediction error < 5.5%, total deviation index < 9.5%, P 10 ≥ 85%), but may be considered for their enhanced clinical feasibility when deemed justified., Conclusions: Our online pharmacometric tool provides an accurate, pragmatic, and ready-to-use technique for measured GFR-based renal function evaluation for clinical situations where conventional methods lack accuracy or show limited feasibility. Additional adaptation and validation of our model and limited sampling schedules for renal transplant recipients with GFRs below 30 mL/min is warranted before considering this technique in these patients., (© 2021. The Author(s).)

Background: The Chronic Kidney Disease in Children Study (CKiD) equation for children and the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation for adults are recommended serum creatinine (SCr)-based calculations for estimating glomerular filtration rate (GFR). However, these equations, as well as their combination, have limitations, notably the problem of implausible changes in GFR during the transition from adolescence to adulthood and overestimation of GFR in young adults. The full age spectrum (FAS) equation addresses these issues but overestimates GFR when SCr levels are low., Objective: To develop and validate a modified FAS SCr-based equation combining design features of the FAS and CKD-EPI equations., Design: Cross-sectional analysis with separate pooled data sets for development and validation., Setting: Research and clinical studies ( n  = 13) with measured GFR available., Patients: 11 251 participants in 7 studies (development and internal validation data sets) and 8378 participants in 6 studies (external validation data set)., Measurements: Clearance of an exogenous marker (reference method), SCr level, age, sex, and height were used to develop a new equation to estimate GFR., Results: The new European Kidney Function Consortium (EKFC) equation is a FAS equation with low bias (-1.2 mL/min/1.73 m 2 [95% CI, -2.7 to 0.0 mL/min/1.73 m 2 ] in children and -0.9 mL/min/1.73 m 2 [CI, -1.2 to -0.5 mL/min/1.73 m 2 ] in adults) across the FAS (2 to 90 years) and SCr range (40 to 490 µmol/L [0.45 to 5.54 mg/dL]) and with fewer estimation errors exceeding 30% (6.5% [CI, 3.8% to 9.1%] in children and 3.1% [CI, 2.5% to 3.6%] in adults) compared with the CKiD and CKD-EPI equations., Limitation: No Black patients were included., Conclusion: The new EKFC equation shows improved accuracy and precision compared with commonly used equations for estimating GFR from SCr levels., Primary Funding Source: Swedish Research Council (Vetenskapsrådet).

An increased albumin-creatinine ratio within the normal range can identify adolescents at higher risk of developing adverse cardio-renal outcomes as they progress into adulthood. Utilizing a parallel randomized controlled trial and observational cohort study, we characterized the progression of vascular phenotypes throughout this important period and investigated the effect of ACE (angiotensin-converting enzyme) inhibitors and statins in high-risk adolescents. Endothelial function (flow-mediated dilation and reactive hyperemia index) and arterial stiffness (carotid-femoral pulse wave velocity) were assessed in 158 high-risk participants recruited to a randomized, double-blind placebo-controlled 2×2 factorial trial (randomized, placebo-controlled trial) of ACE inhibitors and/or statins in adolescents with type 1 diabetes (AdDIT [Adolescent Type 1 Diabetes cardio-renal Intervention Trial]). Identical measures were also assessed in 215 lower-risk individuals recruited to a parallel observational study. In the randomized, placebo-controlled trial, high-risk patients randomized to ACE inhibitors had improved flow-mediated dilation after 2 to 4 years of follow-up (mean [95% CI]: 6.6% [6.0-7.2] versus 5.3% [4.7-5.9]; P =0.005), whereas no effect was observed following statin use (6.2% [5.5-6.8] versus 5.8% [5.1-6.4]; P =0.358). In the observational study, patients classed as high-risk based on albumin-creatinine ratio showed evidence of endothelial dysfunction at the end of follow-up (flow-mediated dilation=4.8% [3.8-5.9] versus 6.3% [5.8-6.7] for high-risk versus low-risk groups; P =0.015). Neither reactive hyperemia index nor pulse wave velocity were affected by either treatment ( P >0.05 for both), but both were found to increase over the duration of follow-up (0.07 [0.03-0.12]; P =0.001 and 0.5 m/s [0.4-0.6]; P <0.001 for reactive hyperemia index and pulse wave velocity, respectively). ACE inhibitors improve endothelial function in high-risk adolescents as they transition through puberty. The longer-term protective effects of this intervention at this early age remain to be determined. Registration- URL: https://www.clinicaltrials.gov; Unique identifier NCT01581476.

Objectives: To identify biomarkers of renal disease in adolescents with type 1 diabetes (T1D) and to compare findings in adults with T1D., Methods: Twenty-five serum biomarkers were measured, using a Luminex platform, in 553 adolescents (median [interquartile range] age: 13.9 [12.6, 15.2] years), recruited to the Adolescent Type 1 Diabetes Cardio-Renal Intervention Trial. Associations with baseline and final estimated glomerular filtration rate (eGFR), rapid decliner and rapid increaser phenotypes (eGFR slopes <-3 and > 3 mL/min/1.73m 2 /year, respectively), and albumin-creatinine ratio (ACR) were assessed. Results were also compared with those obtained in 859 adults (age: 55.5 [46.1, 64.4) years) from the Scottish Diabetes Research Network Type 1 Bioresource., Results: In the adolescent cohort, baseline eGFR was negatively associated with trefoil factor-3, cystatin C, and beta-2 microglobulin (B2M) (B coefficient[95%CI]: -0.19 [-0.27, -0.12], P = 7.0 × 10 -7 ; -0.18 [-0.26, -0.11], P = 5.1 × 10 -6 ; -0.12 [-0.20, -0.05], P = 1.6 × 10 -3 ), in addition to clinical covariates. Final eGFR was negatively associated with osteopontin (-0.21 [-0.28, -0.14], P = 2.3 × 10 -8 ) and cystatin C (-0.16 [-0.22, -0.09], P = 1.6 × 10 -6 ). Rapid decliner phenotype was associated with osteopontin (OR: 1.83 [1.42, 2.41], P = 7.3 × 10 -6 ), whereas rapid increaser phenotype was associated with fibroblast growth factor-23 (FGF-23) (1.59 [1.23, 2.04], P = 2.6 × 10 -4 ). ACR was not associated with any of the biomarkers. In the adult cohort similar associations with eGFR were found; however, several additional biomarkers were associated with eGFR and ACR., Conclusions: In this young population with T1D and high rates of hyperfiltration, osteopontin was the most consistent biomarker associated with prospective changes in eGFR. FGF-23 was associated with eGFR increases, whereas trefoil factor-3, cystatin C, and B2M were associated with baseline eGFR., (© 2020 The Authors. Pediatric Diabetes published by John Wiley & Sons Ltd.)

Primary coenzyme Q 10 (CoQ 10 ) deficiency is unique among mitochondrial respiratory chain disorders in that it is potentially treatable if high-dose CoQ 10 supplements are given in the early stages of the disease. While supplements improve peripheral abnormalities, neurological symptoms are only partially or temporarily ameliorated. The reasons for this refractory response to CoQ 10 supplementation are unclear, however, a contributory factor may be the poor transfer of CoQ 10 across the blood-brain barrier (BBB). The aim of this study was to investigate mechanisms of CoQ 10 transport across the BBB, using normal and pathophysiological (CoQ 10 deficient) cell culture models. The study identifies lipoprotein-associated CoQ 10 transcytosis in both directions across the in vitro BBB. Uptake via SR-B1 (Scavenger Receptor) and RAGE (Receptor for Advanced Glycation Endproducts), is matched by efflux via LDLR (Low Density Lipoprotein Receptor) transporters, resulting in no "net" transport across the BBB. In the CoQ 10 deficient model, BBB tight junctions were disrupted and CoQ 10 "net" transport to the brain side increased. The addition of anti-oxidants did not improve CoQ 10 uptake to the brain side. This study is the first to generate in vitro BBB endothelial cell models of CoQ 10 deficiency, and the first to identify lipoprotein-associated uptake and efflux mechanisms regulating CoQ 10 distribution across the BBB. The results imply that the uptake of exogenous CoQ 10 into the brain might be improved by the administration of LDLR inhibitors, or by interventions to stimulate luminal activity of SR-B1 transporters.

Objective: To assess the contribution of maternal and placental factors to the development of superimposed preeclampsia in women with chronic hypertension., Methods: Endothelial and renal function markers were serially assessed in 90 pregnant women with chronic hypertension and controls., Results: Syndecan-1 concentrations were lower at 26-27 +6  weeks in women with chronic hypertension who subsequently developed superimposed preeclampsia compared with those who did not. Decreased PlGF and raised urine albumin:creatinine ratio were also associated with development of superimposed preeclampsia., Conclusion: Decreased syndecan-1 and PlGF concentrations implicate endothelial glycocalyx disturbance and reduced placental angiogenic capacity, respectively, in the pathophysiology of superimposed preeclampsia.

Background: The Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) creatinine equation is routinely used to assess renal function but exhibits varying accuracy depending on patient characteristics and clinical presentation. The overall aim of the present study was to assess if and to what extent glomerular filtration rate (GFR) estimation based on creatinine can be improved., Methods: In a cross-sectional analysis covering the years 2003-17, CKD-EPI was validated against measured GFR (mGFR; using various tracer methods) in patients with high likelihood of chronic kidney disease (CKD; five CKD cohorts, n  = 8365) and in patients with low likelihood of CKD (six community cohorts, n  = 6759). Comparisons were made with the Lund-Malmö revised equation (LMR) and the Full Age Spectrum equation., Results: 7In patients aged 18-39 years old, CKD-EPI overestimated GFR with 5.0-16 mL/min/1.73 m 2 in median in both cohort types at mGFR levels <120 mL/min/1.73 m 2 . LMR had greater accuracy than CKD-EPI in the CKD cohorts (P 30 , the percentage of estimated GFR within 30% of mGFR, 83.5% versus 76.6%). CKD-EPI was generally the most accurate equation in the community cohorts, but all three equations reached P 30 above the Kidney Disease Outcomes Quality Initiative benchmark of 90%., Conclusions: None of the evaluated equations made optimal use of available data. Prospects for improved GFR estimation procedures based on creatinine exist, particularly in young adults and in settings where patients with suspected or manifest CKD are investigated., (© The Author(s) 2020. Published by Oxford University Press on behalf of ERA-EDTA.)

Objective: Suboptimal adherence to insulin treatment is a main issue in adolescents with type 1 diabetes. However, to date, there are no available data on adherence to adjunct noninsulin medications in this population. Our aim was to assess adherence to ACE inhibitors and statins and explore potential determinants in adolescents with type 1 diabetes., Research Design and Methods: There were 443 adolescents with type 1 diabetes recruited into the Adolescent Type 1 Diabetes Cardio-Renal Intervention Trial (AdDIT) and exposed to treatment with two oral drugs-an ACE inhibitor and a statin-as well as combinations of both or placebo for 2-4 years. Adherence was assessed every 3 months with the Medication Event Monitoring System (MEMS) and pill count., Results: Median adherence during the trial was 80.2% (interquartile range 63.6-91.8) based on MEMS and 85.7% (72.4-92.9) for pill count. Adherence based on MEMS and pill count dropped from 92.9% and 96.3%, respectively, at the first visit to 76.3% and 79.0% at the end of the trial. The percentage of study participants with adherence ≥75% declined from 84% to 53%. A good correlation was found between adherence based on MEMS and pill count ( r = 0.82, P < 0.001). Factors associated with adherence were age, glycemic control, and country., Conclusions: We report an overall good adherence to ACE inhibitors and statins during a clinical trial, although there was a clear decline in adherence over time. Older age and suboptimal glycemic control at baseline predicted lower adherence during the trial, and, predictably, reduced adherence was more prevalent in subjects who subsequently dropped out., (© 2020 by the American Diabetes Association.)

Background Quantification of plasma amino acids is key to the diagnosis of inherited defects of amino acid synthesis, catabolism and transport, many of which present as clinical emergencies. The utility of this test is limited by the long analysis time and subsequent inability of laboratories to provide results in real-time. Traditionally, analysis has been performed by ion exchange chromatography (IEC) but recently there has been a move towards liquid chromatography tandem mass spectrometry (LC-MS/MS) which provides the potential for faster analysis. However, the necessity to derivatise the sample and/or utilise an ion-pair reagent, combined with lack of commercially available stable isotope internal standards (IS) has prevented laboratories fully exploiting the benefits of this methodology. We describe an underivatised LC-MS/MS method enabling patient results to be reported with an improved turnaround time (<1 h). Methods Methanolic IS was added to plasma (10 μL) to precipitate protein. Following centrifugation amino acids were analysed by LC-MS/MS using selected reaction monitoring (SRM) for each analyte and corresponding IS. Results Patient samples (n = 57) and external quality assessment (EQA) material (n = 11) were analysed and results compared with IEC. Comparable accuracy and precision were obtained with 15-min analysis time. Conclusions This method enables the analysis of a clinically comprehensive amino acid profile without the need for derivatisation/ion-pair reagents and benefitting from improved analytical quantitation through multipoint calibration and use of stable isotope IS. The analysis time is fast in comparison to IEC, improves efficiency of laboratory workflow and enables stat analysis of clinically urgent samples.

Aims/hypothesis: We examined whether candidate biomarkers in serum or urine can improve the prediction of renal disease progression in type 1 diabetes beyond prior eGFR, comparing their performance with urinary albumin/creatinine ratio (ACR)., Methods: From the population-representative Scottish Diabetes Research Network Type 1 Bioresource (SDRNT1BIO) we sampled 50% and 25% of those with starting eGFR below and above 75 ml min -1 [1.73 m] -2 , respectively (N = 1629), and with median 5.1 years of follow-up. Multiplexed ELISAs and single molecule array technology were used to measure nine serum biomarkers and 13 urine biomarkers based on our and others' prior work using large discovery and candidate studies. Associations with final eGFR and with progression to <30 ml min -1 [1.73] m -2 , both adjusted for baseline eGFR, were tested using linear and logistic regression models. Parsimonious biomarker panels were identified using a penalised Bayesian approach, and their performance was evaluated through tenfold cross-validation and compared with using urinary ACR and other clinical record data., Results: Seven serum and seven urine biomarkers were strongly associated with either final eGFR or progression to <30 ml min -1 [1.73 m] -2 , adjusting for baseline eGFR and other covariates (all at p<2.3 × 10 -3 ). Of these, associations of four serum biomarkers were independent of ACR for both outcomes. The strongest associations with both final eGFR and progression to <30 ml min -1 [1.73 m] -2 were for serum TNF receptor 1, kidney injury molecule 1, CD27 antigen, α-1-microglobulin and syndecan-1. These serum associations were also significant in normoalbuminuric participants for both outcomes. On top of baseline covariates, the r 2 for prediction of final eGFR increased from 0.702 to 0.743 for serum biomarkers, and from 0.702 to 0.721 for ACR alone. The area under the receiver operating characteristic curve for progression to <30 ml min -1 [1.73 m] -2 increased from 0.876 to 0.953 for serum biomarkers, and to 0.911 for ACR alone. Other urinary biomarkers did not outperform ACR., Conclusions/interpretation: A parsimonious panel of serum biomarkers easily measurable along with serum creatinine may outperform ACR for predicting renal disease progression in type 1 diabetes, potentially obviating the need for urine testing.

Aims: High-density lipoprotein (HDL) function may be altered in patients with chronic disease, transforming the particle from a beneficial vasoprotective molecule to a noxious pro-inflammatory equivalent. Adolescents with Type 1 diabetes often have elevated HDL, but its vasoprotective properties and relationship to endothelial function have not been assessed., Methods and Results: Seventy adolescents with Type 1 diabetes (age 10-17 years) and 30 age-matched healthy controls supplied urine samples for the measurement of early renal dysfunction (albumin:creatinine ratio; ACR), blood samples for the assessment of cardiovascular risk factors (lipid profiles, HDL functionality, glycaemic control, and inflammatory risk score), and had their conduit artery endothelial function tested using flow-mediated dilation (FMD). HDL-c levels (1.69 ± 0.41 vs. 1.44 ± 0.29mmol/L; P < 0.001), and glycated haemoglobin (HbA1c) (8.4 ± 1.2 vs. 5.4 ± 0.2%; P < 0.001) were increased in all patients compared with controls. However, increased inflammation and HDL dysfunction were evident only in patients who also had evidence of early renal dysfunction (mean ± standard deviation for high-ACR vs. low-ACR and healthy controls: inflammatory risk score 11.3 ± 2.5 vs. 9.5 ± 2.4 and 9.2 ± 2.4, P < 0.01; HDL-mediated nitric-oxide bioavailability 38.0 ± 8.9 vs. 33.3 ± 7.3 and 25.0 ± 7.7%, P < 0.001; HDL-mediated superoxide production 3.71 ± 3.57 vs. 2.11 ± 3.49 and 1.91 ± 2.47nmol O2 per 250 000 cells, P < 0.05). Endothelial function (FMD) was impaired only in those who had both a high inflammatory risk score and high levels of HDL-c (P < 0.05)., Conclusion: Increased levels of HDL-c commonly observed in individuals with Type 1 diabetes may be detrimental to endothelial function when accompanied by renal dysfunction and chronic inflammation., (© The Author(s) 2019. Published by Oxford University Press on behalf of the European Society of Cardiology.)

Aims/hypothesis: We aimed to identify a sparse panel of biomarkers for improving the prediction of renal disease progression in type 1 diabetes., Methods: We considered 859 individuals recruited from the Scottish Diabetes Research Network Type 1 Bioresource (SDRNT1BIO) and 315 individuals from the Finnish Diabetic Nephropathy (FinnDiane) study. All had an entry eGFR between 30 and 75 ml min -1 [1.73 m] -2 , with those from FinnDiane being oversampled for albuminuria. A total of 297 circulating biomarkers (30 proteins, 121 metabolites, 146 tryptic peptides) were measured in non-fasting serum samples using the Luminex platform and LC electrospray tandem MS (LC-MS/MS). We investigated associations with final eGFR adjusted for baseline eGFR and with rapid progression (a loss of more than 3 ml min -1 [1.73 m] -2  year -1 ) using linear and logistic regression models. Panels of biomarkers were identified using a penalised Bayesian approach, and their performance was evaluated through 10-fold cross-validation and compared with using clinical record data alone., Results: For final eGFR, 16 proteins and 30 metabolites or tryptic peptides showed significant association in SDRNT1BIO, and nine proteins and five metabolites or tryptic peptides in FinnDiane, beyond age, sex, diabetes duration, study day eGFR and length of follow-up (all at p < 10 -4 ). The strongest associations were with CD27 antigen (CD27), kidney injury molecule 1 (KIM-1) and α1-microglobulin. Including the Luminex biomarkers on top of baseline covariates increased the r 2 for prediction of final eGFR from 0.47 to 0.58 in SDRNT1BIO and from 0.33 to 0.48 in FinnDiane. At least 75% of the increment in r 2 was attributable to CD27 and KIM-1. However, using the weighted average of historical eGFR gave similar performance to biomarkers. The LC-MS/MS platform performed less well., Conclusions/interpretation: Among a large set of associated biomarkers, a sparse panel of just CD27 and KIM-1 contains most of the predictive information for eGFR progression. The increment in prediction beyond clinical data was modest but potentially useful for oversampling individuals with rapid disease progression into clinical trials, especially where there is little information on prior eGFR trajectories.