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Measurement of the serum levels of vitamin B12 (VB12) is key for evaluating VB12 deficiency-dependent anemia. Immunoassay, the major method for determining VB12, tends to give false-normal results because of the presence of anti-intrinsic factor (IF-Ab) or other factors such as heterophilic antibodies et al. This study aimed to develop a liquid chromatography tandem mass spectrometry (LC-MS/MS) method that is helpful for distinguish false normal VB12 results measured by the immunoassay. Different forms of VB12 were derivatized into CN-B12, which was collected through solid-phase extraction and analyzed via LC-MS/MS. 236 serum samples were measured both by LC-MS/MS and immunoassay, results were compared, and the IF-Ab effect was evaluated. The LC-MS/MS assay afforded a linear slope from 20 to 4,000 pmol/L for CN-B12. OH-VB12, methyl-VB12, and CoA-VB12 showed recovery within 89.3–109.5%. The intra-assay CV of VB12 was 2.6–4.1%, whereas the total CV was 9.3–9.8%. Passing–Bablok regression between LC-MS/MS and immunoassay results showed that the slope was 1.085 and the intercept was −15.691. The Bland–Altman plot showed that the mean difference and difference% were −34.6 pmol/L and 0.3%, respectively. Inter-rater agreement analysis showed that the linear weighted kappa value was 0.885, implying good agreement between the two methods. However, two samples were falsely elevated and one sample was falsely normal in the immunoassay compared with LC-MS/MS. The LC-MS/MS method helped in the distinction of false-normal VB12 results shown by the immunoassay. The VB12 LC-MS/MS method can be used as an arbiter of clinically discordant immunoassay results. [ABSTRACT FROM AUTHOR]

A trueness-based EQA/PT program for high density lipoprotein cholesterol (HDL-C) was initiated. We analyzed the 4 year EQA/PT program to overview the measurement standardization for HDL-C in China. Two levels of freshly frozen, commutable serum external quality assessment/proficiency testing (EQA/PT) materials were prepared and determined by reference measurement procedure each year. The samples were delivered to clinical laboratories and measured 15 times in 3 days. The precision [coefficient of variation (CV)], trueness (bias), and accuracy [total error (TE)] were calculated and used to evaluate measurement performance. The pass rates of individual laboratories and peer groups were analyzed using the acceptable performance from the National Cholesterol Education Program (NCEP) and biological variation as the evaluation criteria. More than 60% of laboratories use heterogeneous systems, and there was a decrease in the percentage from 2016 to 2019. About 95, 78, and 33% of laboratories met the minimum, desirable and optimum TE criteria derived from biological variation. The pass rates were 87.0% (84.7–88.8%), 58.7% (55.3–62.4%), and 97.3% (95.6–98.3%) that met the acceptable performance of TE, bias, and CV of NCEP. The homogeneous systems had higher pass rates of TE, bias, and CV than the heterogeneous groups in 2016, but they did not show apparent advantages in 2017–2019. The trueness-based EQA/PT program can be used to evaluate the accuracy, reproducibility, and trueness of results. For some IVD manufacturers and individual laboratories, accuracy, especially trueness, are still problems. Efforts should be made to improve the situation and achieve better HDL-C measurement standardization. [ABSTRACT FROM AUTHOR]

Background: This study aimed to quantify and compare serum aldosterone (sALD) levels through three different chemiluminescence immunoassays (CLIAs) and liquid chromatography tandem mass spectrometry (LC-MS/MS) analysis. Methods: Serum samples from 221 patients with suspected primary aldosteronism (PA) were retrospectively included in this study conducted at the Peking Union Medical College Hospital from June to August in 2017. sALD levels were determined using the LC-MS/MS method and three different CLIA systems, viz., DiaSorin® XL, iSYS and Auto Lumo A2000. Pooled fresh serum samples were used for recalibration. Passing-Bablok regression analysis, correlation matrix, and Bland-Altman plots were used to evaluate the concurrence among ALD levels determined using the three CLIAs. Results: Within-laboratory precision of the four assays ranged from 2.1% to 9.4%, except the coefficient variation (CV) of one of the CLIAs, which exceeded 20.0% for samples with low sALD levels. sALD levels determined using LC-MS/MS were significantly lower than those determined using the other three CLIAs (p < 0.0001). Spearman's correlation coefficient of the four assays ranged from 0.745 to 0.950 (p < 0.0001). The Bland-Altman plot showed that the average bias (%) for the three CLIAs and LC-MS/MS ranged from −69.3 to −49.2. After recalibration, this correlation did not improve among the assays. However, the bias and bias percentage at the medical decision level improved between LC-MS/MS and DiaSorin® XL/iSYS. Conclusions: Significant inconsistencies between the results of CLIAs and LC-MS/MS indicate that different sALD measures cannot be used interchangeably. [ABSTRACT FROM AUTHOR]

Background: Thyroid hormone levels are essential for diagnosing and monitoring thyroid diseases. However, their reference intervals (RIs) in elderly Chinese individuals remain unclear. We aimed to identify factors affecting thyroid-stimulating hormone (TSH), free triiodothyronine (FT3), and free thyroxine (FT4) levels using clinical "big data" to establish hormone level RIs for elderly Chinese individuals. Methods: We examined 6781, 6772, and 6524 subjects aged ≥65 years who underwent FT3, FT4, and TSH tests, respectively, at the Peking Union Medical College Hospital between September 1, 2013, and August 31, 2016. Hormones were measured using an automated immunoassay analyzer (ADVIA Centaur XP). RIs were established using the Clinical Laboratory Standards Institute document C28-A3 guidelines. Results: The median TSH was significantly higher in women than in men; the opposite was true for median FT3 and FT4 levels. No differences were observed in TSH or FT4 by age in either sex or overall; FT3 levels significantly decreased with age. Seasonal differences were observed in TSH and FT3 levels but not FT4 levels; the median TSH was the highest in winter and lowest in summer, whereas the median FT3 was the lowest in summer (albeit not significantly). RIs for TSH were 0.53–5.24 and 0.335–5.73 mIU/L for men and women, respectively; those for FT3 were 3.76–5.71, 3.60–5.42, and 3.36–5.27 pmol/L in 64- to 74-, 75- to 84-, and 85- to 96-year-old subjects, respectively. The RI for FT4 was 11.70–20.28 pmol/L. Conclusions: RIs for TSH in elderly individuals were sex specific, whereas those for FT3 were age specific. [ABSTRACT FROM AUTHOR]

Background: The demand for vitamin D testing is increasing in China. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) immunoassay is specific and accurate but requires expensive equipment, experienced operators, and complicated pretreatment of serum. Automated immunoassays are simple and convenient but only determine total 25-hydroxyvitamin D (25OHD). The objective of this study was to quantify 25OHD2 and 25OHD3 in patients to assist clinical physicians and laboratory directors in choosing the most appropriate method to determine 25OHD. Methods: Vitamin D testing was conducted for 23,695 patients in Peking Union Medical College Hospital from May 2015 to January 2017. Using this large data set, the prevalence and levels of 25OHD2 were analyzed. LC-MS/MS was used to separately determine 25OHD2 and 25OHD3. Results: 25OHD2 (≥2.5 ng/mL) was detected in 16.4% (3877/23,695) of patients. Males had a significantly lower incidence of detectable 25OHD2 (p < 0.01); 1077 (13.9%) samples contained detectable 25OHD2 (median: 3.7 ng/mL; 2.5%-97.5%: 2.5-17.2 ng/mL). For females, 2800 (17.5%) samples contained detectable 25OHD2 (median: 4.0 ng/mL; range: 2.5-20.6 ng/mL). Of the 3877 patients with detectable 25OHD2, males had a significantly higher level of 25OHD3 (p < 0.01). There was no significant difference in total 25OHD. The proportion of 25OHD2 in total 25OHD was 1.3%-100%; 87.5% (3391/3877) of the samples contained <10 ng/mL 25OHD2. 25OHD2 negatively correlated with 25OHD3 (r = -0.197, p < 0.01) and positively correlated with total 25OHD (r = 0.217, p < 0.01). Conclusions: Prevalence of 25OHD2 in patients tested for vitamin D is relatively high in China. 25OHD2 is significantly negatively correlated with 25OHD3. [ABSTRACT FROM AUTHOR]

Background: The relationship between fractional cholesterol esterification rate in plasma or serum high-density lipoprotein (HDL) (FERHDL) and lipoprotein subfractions and other cardiovascular disease (CVD) risk factors has been demonstrated. However, the current method for measuring FERHDL requires fresh serum samples and radioactive labeling of the samples, making it impractical for use in clinical laboratories. In this study, we developed a simple and precise HPLC method for the measurement of FERHDL. Correlations between FERHDL and CVD risk factors were evaluated in 119 healthy volunteers. Methods: Fasting blood samples were collected and serum was isolated within 2 h. Serum HDL was prepared by precipitation of apolipoprotein B (apoB)-containing lipoproteins with dextran sulfate and magnesium chloride. HDL fractions were divided into two aliquots and incubated at 0°C and 37°C, respectively, for 1 h. Free cholesterol in the HDL fractions was analyzed by HPLC. FERHDL was calculated as the percent decrease of free cholesterol during incubation. Results: The esterification reaction of HDL free cholesterol was not linear, but the measured FERHDL was stable when serum samples were stored at room temperature for <4 h, or at 4°C for <24 h. The intra-assay and total CVs for FERHDL measurements were 1.0%-2.1% and 1.6%-3.8%, respectively. Results of 119 healthy volunteers showed that FERHDL was positively correlated with age, BMI, blood pressure, total cholesterol (TC), triglyceride (TG) and small dense low-density lipoprotein-cholesterol (LDLb-C), and negatively correlated with HDL-C and HDL2-C. FERHDL has shown to be a predictor of HDL and LDL subfraction distributions. Conclusions: This method is simple, non-radioactive and precise and will be useful in prediction of lipoprotein subfraction distributions and in clinical assessment of CVD risks. [ABSTRACT FROM AUTHOR]