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Introduction: Clinical laboratories should guarantee sample stability in specific storage conditions for further analysis. The aim of this study is to evaluate the stability of plasma samples under refrigeration for 29 common biochemical analytes usually ordered within an emergency context, in order to determine the maximum allowable period for conducting add-on testing. Materials and methods: A total of 20 patient samples were collected in lithium heparin tubes without gel separator. All analyses were performed using Alinity systems (Abbott Laboratories, Abbott Park, USA) and samples were stored at 2-8 °C. Measurements were conducted in primary plasma tubes at specific time points up to 48 hours, with an additional stability study in plasma aliquots extending the time storage up to 96 hours. The stability limit was estimated considering the total limit of change criteria. Results: Of the 29 studied parameters, 24 demonstrated stabilities within a 48-hour storage period in primary plasma tubes. However, five analytes: aspartate aminotransferase, glucose, lactate dehydrogenase, inorganic phosphate and potassium evidenced instability at different time points (7.9 hours, 2.7 hours, 2.9 hours, 6.2 hours and 4.7 hours, respectively). The stability study in plasma aliquots showed that all parameters remained stable for 96 hours, except lactate dehydrogenase, with a stability limit of 63 hours. Conclusions: A reduced stability of primary plasma samples was observed for five common biochemical analytes ordered in an emergency context. To ensure the quality of add-on testing for these samples, plasma aliquots provide stability for a longer period. [ABSTRACT FROM AUTHOR]

Background: It is recommended that samples for plasma ammonia analysis are kept chilled and processed promptly as in vitro metabolism causes falsely elevated results. Rejection of unsuitable samples can cause delayed diagnosis and treatment of hyperammonaemia with potentially serious clinical consequences. The Metabolic Biochemistry Network (MetBioNet) hyperammonaemia guideline recommends analysis of samples not collected under ideal conditions and reporting with appropriate comments. An audit found that some laboratories did not follow this guidance. An investigation was performed into whether storage at controlled room temperature and delayed sample processing affected interpretation of plasma ammonia results. Methods: Eleven healthy volunteers provided informed consent. Blood was taken from each into 14 paediatric EDTA blood sample tubes, one placed immediately on ice, the others in a rack at room temperature. The chilled and baseline room temperature samples were centrifuged and plasma analysed by the Roche Ammonia (NH3L2) method. Samples stored at room temperature were analysed at 10-min intervals up to 2 h. Results: Baseline room temperature ammonia was higher than in the chilled sample (19 ± 6.6 µmol/L [mean ± standard deviation] and 18 ± 6.6 µmol/L, respectively). Ammonia increased further by 0.09 ± 0.02 µmol/L per minute to 30 ± 8.4 µmol/L at 2 h. No result was above the reference range (50 µmol/L). No healthy subject with normal baseline ammonia would have been erroneously identified as having hyperammonaemia. Conclusions: Results support MetBioNet guidance that laboratories accept blood samples for ammonia analysis which are not processed under ideal conditions. [ABSTRACT FROM AUTHOR]

Although the use of cryoprotectant dimethyl sulfoxide (DMSO) is the gold standard in cryopreservation of hematopoietic stem cells, it is well known that it has a negative effect on cell viability. The aim of this prospective study was to examine how the length of post-thaw exposure to DMSO affects the cell viability and stability of peripheral blood stem cell (PBSC) samples. Additionally, the effects of donor type and pre-cryopreservation storage time on post-thaw viability during the stability study were evaluated. In 30 autologous and 30 allogeneic PBSC samples viable CD34+, CD14+, CD19+, CD16+/56+, and CD3+ cells were determined immediately after thawing, and one-and three-hours post-thaw.

C-peptide and insulin are peptide hormones and their stability is affected by a number of pre-analytical factors. The study aimed to investigate the impact of sample type, storage temperature and time delays before centrifugation and analysis on the stability of C-peptide and insulin. Ten healthy non-diabetic adults in fasting and non-fasting state were enrolled. 40 mL of blood was collected from each participant into SST and dipotassium EDTA tubes. Samples were centrifuged immediately or at timed intervals (8, 12, 48 and 72 h). After baseline measurements on the Roche Cobas e602 analyzer using electrochemiluminescence immunoassays, aliquots were stored at room temperature (RT), 2–8 and −20 °C for 4 h to 30 days. The percentage deviation (PD) from baseline was calculated and a change greater than desirable biological variation total error was considered clinically significant. C-peptide was more stable in separated serum than plasma (PD of −5 vs. −13 %) samples stored at 2–8 °C for 7 days and was most unstable at RT when centrifugation was delayed (PD −46 % in plasma and −74 % in serum after 48 h). Insulin was more stable in plasma than in serum under the different storage conditions with a minimum PD of −1% when stored at −20 °C for 30 days. When samples were kept unspun at RT for 72 h, PD was −23 and −80 % in plasma and serum, respectively. C-peptide was more stable in serum provided the sample was centrifuged immediately and stored in the fridge or freezer while insulin was found to be more stable in EDTA plasma. [ABSTRACT FROM AUTHOR]

Knowledge of the stability of analytes in clinical specimens is a prerequisite for proper transport and preservation of samples to avoid laboratory errors. The new version of ISO 15189:2022 and the European directive 2017/746 increase the requirements on this topic for manufacturers and laboratories. Within the project to generate a stability database of European Federation of Clinical Chemistry and Laboratory Medicine (EFLM) Working Group Preanalytical Phase (WG-PRE), the need to standardise and improve the quality of published stability studies has been detected, being a manifest deficit the absence of international guidelines for the performance of stability studies on clinical specimens. These recommendations have been developed and summarised by consensus of the WG-PRE and are intended primarily to improve the quality of sample stability claims included in information for users provided by assay supplier companies, according to the requirements of the new European regulations and standards for accreditation. This document provides general recommendations for the performance of stability studies, oriented to the estimation of instability equations in the usual working conditions, allowing flexible adaptation of the maximum permissible error specifications to obtain stability limits adapted to the intended use. We present this recommendation based on the opinions of the EFLM WG-PRE group for the standardisation and improvement of stability studies, with the intention to improve the quality of the studies and the transferability of their results to laboratories. [ABSTRACT FROM AUTHOR]

Background: The determination of iCa and iMg is important in veterinary medicine, but their immediate determination in whole blood is not always possible. Their stability in other sample types and the existence of interferences must be evaluated before its use. Objectives: We aimed to analyze the effects of storage time on the stability of iCa, iMg, and other analytes in whole blood, plasma, and serum samples in horses and assess the interference of heparin in these measurements. Methods: Whole blood, heparin‐plasma, and serum samples from 10 horses were stored at 4°C and analyzed 1, 2, 3, 4, 5, 6, 7, 8, 24, 48, and 168 hours after sample collection using the Stat Profile Prime Plus Vet equipment (Nova Biomedical, Waltham, MA, USA). Results were analyzed by ANOVA or mixed‐effect models. Results: The concentration of iCa, iMg, total calcium (tCa), total magnesium (tMg), and the ratios iCa/tCa and iMg/tMg did not differ up to 168 hours when compared to the initial time. Total Ca, iMg, and tMg were not significantly different among sample types, but iCa concentrations were slightly but significantly lower in plasma. Freezing at −20°C did not affect iCa, iMg, tCa, and tMg. The pH increased in serum and plasma after 8 hours, and a mild negative correlation existed between plasma iCa concentration and pH. A negative correlation was observed also between the ratios iCa/tCa or iMg/tMg and pH in plasma and serum. A significant decrease in iCa and iMg was detected when comparing homemade syringes at high heparin concentration (~200–300 U heparin/mL) and commercial lithium‐heparin tubes (20–30 U/mL). Conclusions: Samples stored at 4°C can be used to determine iCa and iMg concentrations up to 7 days after collection. Other metabolites are stable for up to 8 hours; heparin interference should be taken into account if using homemade heparin syringes. [ABSTRACT FROM AUTHOR]

• Hb concentration decreases in FIT specimens with storage, which may lead to false negatives. • FIT specimens with initial results near the clinical cut-off are more susceptible to false negatives. • Specimen storage temperature impacts the stability of FIT specimens. • Laboratories should validate FIT specimen storage conditions to help prevent false negatives. Fecal immunochemical tests (FIT) are used to screen for colorectal cancer by detecting blood present in stool. Patients collect FIT specimens at home in a sampling kit and return them to the lab for testing. At our institution, patients are instructed to return their specimens to the laboratory within seven days from collection, which is shorter than the manufacturer stated room temperature (RT) stability of 15 days. The objective of this study was to assess and verify the stability of FIT specimens at RT and to determine if refrigerated storage improves stability. A series of experiments were performed with the OC-Sensor DIANA iFOB Test system between 2017 and 2019, using a positive clinical cut-off of 75 ng/mL (15 µg/g) hemoglobin (Hb). Specimens were collected and categorized based on their initially measured Hb concentration and had repeated measurements for up to 21 days following collection. FIT specimens were stored either at RT or refrigerated. Our results show that FIT specimens have reduced concentrations of Hb compared to baseline when stored at RT; refrigeration improved FIT specimen stability but did not completely prevent the reduction in Hb concentration. Additionally, specimens marginally above the cut-off (initial concentrations between 75 and 100 ng/mL (15–20 µg/g)) that were stored at RT showed 100% positivity on the day of collection (n=33), 63% on Day 3 (n=19), 46% on Days 4/5 (n=26), and 38% on Days 6/7 (n=26). Finally, specimens with Hb values near the clinical cut-off appear to be particularly susceptible to false negatives as a result of the reduction in Hb over time. Therefore, laboratories should verify the specifics of their FIT tests before offering it to patients to reduce false negatives. [ABSTRACT FROM AUTHOR]

Introduction: We define a designated data analytics workflow for the evaluation of stability experiments, which takes all data situations into account. This complements the evaluation described by the CLSI EP25 [1] guideline by including a targeted exception handling algorithm and thus allows one to automatically evaluate stability data based on linear regression analysis. Description: The evaluation of stability experiments based on regression analysis requires the calculation of the confidence interval of the regression line. The stability time is estimated at the intersection of the confidence interval with the acceptance criterion. This approach results in solving a quadratic equation, with factors that depend on the estimated intercept, slope, the measurement variability and the chosen timepoints. When defining an automated data analytics workflow for this problem, the different cases for the solutions of the quadratic equation must be considered. For some data situations there might be no solution at all, other data situations result in a negative and a positive solution and finally there might be even two positive solutions. All these cases have to be considered for the choice of the right solution to become the estimated stability time. The CLSI EP25 [1] guideline on stability evaluation of in vitro diagnostic reagents addresses this problem only superficially and might even lead to incorrect results for some specific data scenarios. Results: We evaluate all possible data scenarios and provide examples for each. Based on the gained theoretical insights, we define a designated data analytics workflow and visualize it with a flowchart. By following this flowchart one can implement an automated analysis workflow, targeting all data scenarios with the appropriate exception handling. Discussion: We deduce that the description for obtaining stability times according to CLSI EP25 is not fully adequate, as it addresses only best-case scenarios. However, for automated data analytics workflows all possible data situations have to be considered. With the here presented workflow one can program automated data analytics pipelines, which ensure that the right stability time is obtained, in case it exists. In addition all exceptions, where no stability times are present, are addressed in the right way and it provides hints as to the failure reason.

Keywords: real-time PCR; sample stability; SARS-CoV-2 EN real-time PCR sample stability SARS-CoV-2 e78 e80 3 04/25/23 20230515 NES 230515 To the Editor, We read with great interest the article "SARS-CoV-2 RNA identification in nasopharyngeal swabs: issues in pre-analytics" by Basso et al. (2020), particularly regarding the findings on sample stability [[1]]. With those results in mind, we aimed to evaluate whether nasopharyngeal swab samples maintained viability for SARS-CoV-2 RNA detection through qRT-PCR following different storage periods in various conditions in southeastern Brazil. The coefficient of variation (CV) of observed Ct from samples maintained at environment temperature ranged from 1.3 to 5.3% for I E i gene; 0.4-6.8% for I RdRp/S i and 0.81-4.8% for I N i gene (data not shown). [Extracted from the article]

• SARS-CoV-2 patient samples covered the range of cycle threshold values. • Split samples were cultured fresh and after storage at 80 °C for 7 or 17-18 days. • Freeze-thaw did not significantly affect SARS-CoV-2 viral culture isolation. • Therefore, frozen samples may be used to assess SARS-CoV-2 infectiousness. The effect of freeze-thaw on SARS-CoV-2 viral viability is not well established. We isolated virus from 31 split clinical samples cultured fresh or after a 7- or 17/18-day freeze. We found that freeze-thaw did not significantly affect viral culture isolation. Therefore, frozen samples may be used to assess SARS-CoV-2 infectiousness. [ABSTRACT FROM AUTHOR]

Samples of biologic specimens and their derivatives (eg, wet tissues, paraffin-embedded tissue blocks, histology slides, frozen tissues, whole blood, serum/plasma, and urine) are routinely collected during the course of nonclinical toxicity studies. Good Laboratory Practice regulations and/or guidance specify minimum requirements for specimen retention duration, with the caveat that retention of biologic specimens need not extend beyond the duration of sample stability. However, limited availability of published data regarding stability for various purposes following storage of each specimen type has resulted in confusion, uncertainty, and inconsistency as to the appropriate duration for storage of these specimens. To address these issues, a working group of the Society of Toxicologic Pathology Scientific and Regulatory Policy Committee was formed to review published information, regulations, and guidance pertinent to this topic and to summarize the current practices and rationales for retention duration through a survey-based approach. Information regarding experiences reaccessing biologic specimens and performing sample stability investigations was also collected. Based on this combined information, the working group developed several points to consider that may be referenced when developing or revising sample retention practices. This Points to Consider article is a product of a Society of Toxicologic Pathology (STP) Working Group commissioned by the Scientific and Regulatory Policy Committee (SRPC) of the STP. It has been reviewed and approved by the SRPC and Executive Committee of the STP, the British Society of Toxicologic Pathologists (BSTP) and European Society of Toxicologic Pathology (ESTP) but it does not represent a formal Best Practice recommendation; rather, it is intended to provide key "points to consider" in designing nonclinical studies or interpreting data from toxicity and safety studies in support of regulatory submissions. The points expressed in this document are those of the authors and do not reflect views or policies of the employing institutions. Readers of Toxicologic Pathology are encouraged to send their thoughts on these articles or ideas for new topics to the Editor. [ABSTRACT FROM AUTHOR]

BackgroundAcute kidney injury (AKI) is associated with increased mortality, morbidity, hospital length of stay, and costs. A quantitative urine test is available to assess the risk of developing AKI by measuring the concentrations of two protein biomarkers, TIMP-2 and IGFBP-7. The NephroCheck Test combines these concentrations into an AKIRisk Score. The purpose of this study is to characterize the analytical performance characteristics of the AKIRisk Score.MethodsLinearity and analytical sensitivity were evaluated by following Clinical Laboratory Standards Institute (CLSI) EP06-A and EP17-A, respectively. Precision was evaluated by testing clinical samples and examining the repeatability of test results. Potential interference was evaluated for endogenous and exogenous substances. Sample stability was examined at room temperature and at 2-8°C, as well as the effect of sample centrifugation temperature on test results.ResultsThe AKIRisk Score exhibits approximately 10% coefficient of variation (CV) at the recommended cutoff value of 0.3 and the limit of quantitation (LoQ) was 0.002. Only albumin, bilirubin (conjugated), and methylene blue interfered with test results, at concentrations exceeding 1250 mg/L, 72 mg/L, and 0.49 mg/L, respectively. AKIRisk Score results were stable for 6h at room temperature, 24h refrigerated, and not impacted by sample centrifugation temperature.ConclusionsOur studies demonstrate that the AKIRisk Score has robust analytical performance, good precision, minimal analytical interference, acceptable sensitivity, and excellent sample stability.

Automated storage and retrieval modules (SRM), as part of total lab automation (TLA) systems, offer tremendous practical and economic benefits. In contrast to manual storage systems, SRMs indicate continuous motion of samples and may leave samples prone to temperature fluctuations. This study investigates analyte stability in serum and heparin plasma within an automated storage module. The stability of 28 common biochemistry analytes was investigated using 57 freshly obtained routine serum samples and 42 lithium-heparin plasma samples. Following baseline measurement, samples were stored at 2–8 °C in the automated SRM of the Accelerator a3600 TLA and reanalyzed at fixed time points (2, 4, 8, 12, 24, 48 and 72 h) on the Abbott Architect c16000 chemistry analyzer. The concentration at each time point was expressed as %-difference to the baseline value and mean results were compared to the criteria for desirable bias derived from the biological variation database. Nine of the analytes exceeded the bias criterion within 72 h after initial measurement in either serum samples, plasma samples or both. Lithium-heparin plasma samples showed increasing values for phosphor, potassium and lactate dehydrogenase (LDH), which were only considered stable for respectively 24, 12 and 4 h, glucose was considered stable for 8 h. Electrolyte concentrations and LDH activity significantly increased in serum samples beyond 48 h. Bicarbonate should not be performed as add-on test at all. The presented data indicate that the conditions within an SRM have no clinical impact on sample stability and allow stable measurement of routine analytes within 72 h, comparable to manual storage facilities. [ABSTRACT FROM AUTHOR]

Freezing is a common way of storing samples including beer samples. To verify the suitability of this procedure, the results of determination of alcohol (% v/v), original gravity, color, pH, thiobarbituric acid index, total polyphenols, saccharides, limit of attenuation, free amino nitrogen, protein nitrogen by coomassie brilliant blue, iso-α-bitter acids, diacetyl, higher alcohols, esters, fatty acids, carbonyl compounds and hop oils in beer, and protein nitrogen by coomassie brilliant blue and total polyphenols in wort were compared before and after freezing the sample. It was found that most determinations were not affected by sample freezing, but the determinations of alcohol, original gravity and total polyphenols were affected. In case these very frequent determinations would need to be performed after freezing, a new uncertainty of the method was calculated for these analyzes. From the spectrum of fifteen tested carbonyl compounds, there was a statistically significant increase in the concentration of four compounds (2-methylpropanal, 2-methylbutanal, 3-methylbutanal, phenylacetaldehyde). A significant decrease after sample freezing was observed for most of the analyzed essential oils.

Point of care testing of residual effect of antiplatelet therapy in trauma patients or during major surgery may result in improved clinical management of significant bleeding. We included 121 healthy individuals (57 females and 64 males, aged 22–65 years) in order to establish reference intervals for platelet aggregation induced by adenosine diphosphate (ADPTEM, 10 µM), arachidonic acid (ARATEM, 0.42 mM) and thrombin activating peptide (TRAPTEM, 36 µM) employing the ROTEM platelet module. Further, the impact of citrate (3.2%) and hirudin (>15 µg/ml) as anticoagulants was evaluated. Finally, we investigated assay stability (15, 30, 60, and 120 min after blood sampling) (n = 8) and between-day variation (n = 5). We report reference intervals for 121 healthy individuals and reference intervals by gender. We observed significantly higher platelet aggregation in females than in males (all P-values < 0.05). No correlation between age and platelet aggregation was observed, except for the parameter TRAPTEM amplitude (A6), in which a decline in A6 was observed with increasing age (P = 0.03). We observed significantly lower levels of platelet aggregation in citrate tubes than in hirudin tubes (all P-values < 0.05), except from TRAPTEM maximum slope, where no significant difference was observed (P = 0.40). The stability was acceptable (≤20% deviation) for up to 120 min for ARATEM in citrate tubes, and up to 60 min for the ADPTEM and TRAPTEM assays in citrate tubes. In hirudin tubes we found ADPTEM and ARATEM assays to be stable for 60 min, while the stability of TRAPTEM in hirudin tubes was found to be stable for 30 min. Using citrate tubes, the between-day variation (mean coefficient of variation, CV) was 19–20% for ADPTEM, 19–26% for TRAPTEM, and 10% for ARATEM, whereas the mean CV was 11–13% for all three assays in hirudin tubes. In conclusion, we established combined and gender-specific reference intervals for three platelet aggregation assays in both citrate- and hirudin tubes. In citrate tubes, the stability of the ROTEM platelet assays was 60–120 min, while the stability in hirudin tubes was 30–60 min. The between-day variation was lowest for samples obtained in hirudin tubes.

In this study, the preservation of As(III) in model solutions and natural groundwater samples from four locations in Croatia was conducted. Model laboratory samples were spiked with As(III) and As(V), and different complexing agents. Solutions were analysed in intervals of 24, 48 h and during ten days after preparation. Model samples containing citric acid, sodium citrate, sodium oxalate and potassium sodium tartrate in combination with acetic acid, spiked with As(III)and As(V), showed good species preservation. As(III), in model samples, was preserved for 7 days with citric acid, and citric acid in combination with acetic acid, as well as with tartrate. As(III), in natural samples, was preserved for 6 to 12 days with potassium sodium tartrate, citric acid, and citric acid in combination with acetic acid and showed improvement, compared with unpreserved samples (oxidation in 3 days). The results showed that acetic acid alone was not successful in preserving As speciation. Good resolution of inorganic arsenic species was achieved using differential pulse anodic stripping voltammetry technique (DPASV). Since this technique is comparatively cheaper and more convenient to use than other available techniques it could become a method of choice for arsenic speciation in water. [ABSTRACT FROM AUTHOR]

Per- and polyfluoroalkyl substances (PFAS) have been extensively used as surfactants because of their high stability and good water/oil-repellent properties. PFASs, especially perfluoroalkyl acids (PFAAs), have long biological half-lives, and exposure may cause adverse health effects in humans. We assessed temporal trends of concentrations of eight PFAAs in serum of Swedish adolescents (age 16–21 years) from the general population, and estimated the stability of PFAAs and serum samples after 6 years of storage. Repeated cross-sectional sampling was performed on five occasions (covering in total 1213 individuals, 83% males) in southern Sweden between 2000 and 2017. We analyzed serum for perfluorohexane sulfonic acid (PFHxS), perfluorooctane sulfonic acid (PFOS), perfluoroheptanoic acid (PFHpA), perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), perfluorodecanoic acid (PFDA), perfluoroundecanoic acid (PFUnDA), and perfluorododecanoic acid (PFDoDA) using liquid chromatography-tandem mass spectrometry. We assessed time trends using linear regression, long-term stability was assessed by reanalyzing samples collected 2013, and the comparison was done using Pearson correlation and Bland-Altman plots.PFHxS, PFOS, and PFOA decreased by 6.7% (CI: –7.0, –6.3%), 12.6% (CI: –12.9, –12.3%), and 6.5% (CI: –6.8, –6.1%) per year, respectively, and year of sampling explained 48–81% of the variation in concentrations. PFNA and PFDA seemed to increase up to 2009 and decrease thereafter. The trends were consistent after sensitivity analyses excluding women. Strong correlations of 94–97% were observed for concentrations of all compounds, except PFHxS, after storage. The observed trends closely followed the timing of manufacturers’ voluntary phase-out initiatives, and of regulatory measures governing the compounds implemented in the EU and USA. This indicates that these actions mitigated the population’s exposure to PFHxS, PFOS, and PFOA and, in recent years, to PFNA and PFDA, in southern Sweden. Furthermore, the results suggest that PFAAs remain stable in serum samples after long-term storage.

A typical metabolomic analysis consists of a multi-step procedure. Variation can be introduced in any analysis segment if proper care in quality assurance is not taken, thus compromising the final results. Sample stability is one of those factors. Although sophisticated studies addressing sample decay over time have been performed in the medical field, they are emerging in plant metabolomics. Here, we focus on the stability of wheat floret extracts on queue inside an auto-injector held at 25 °C. The objective was to locate an analytical time window from extraction to injection with no significant difference occurring in the sample. Total ion current chromatograms, principal component analysis, and volcano plots were used to measure changes in the samples. Results indicate a maximum work window time of 7:45 h for Steele-ND wheat methanolic extractions in an auto-sampler at 25 °C. Comparisons showed a significant gradual increase in the number and intensity of compounds observed that may be caused by the degradation of other molecules in the sample extract. The approach can be applied as preliminary work in a metabolite profiling study, helping to set the appropriate workload to produce confident results.

In this study, a rapid (less than 10 min) analytical method by reverse-phase supercritical fluid chromatography was developed with an isocratic mobile phase, enabling the separation of 11 compounds, chlorophyll a and b, pheophytin a and numerous allomers or epimers. This method was used to examine the stability of chlorophyll pigments of plant extracts obtained with various extraction methods including microwave-assisted extraction (MAE), supercritical fluid extraction (SFE), pressurized liquid extraction (PLE) and ultrasound-assisted extraction (UAE), with ethanol as solvent or modifier. The effect of storage was studied for both liquid and dried extracts. Irrespective of the extraction method, the evaporation of the extracts induced partial degradation of the chlorophyll pigments. It was found that liquid extracts could be stored at 4 °C for 3 weeks without a dramatic change in allomer forms of chlorophylls. However, during this storage period, epimerization appears to be important, leading to a significant decrease in the chlorophyll b native form. [ABSTRACT FROM AUTHOR]

Freezing is a common way of storing samples including beer samples. To verify the suitability of this procedure, the results of determination of alcohol (% v/v), original gravity, color, pH, thiobarbituric acid index, total polyphenols, saccharides, limit of attenuation, free amino nitrogen, protein nitrogen by coomassie brilliant blue, iso-a-bitter acids, diacetyl, higher alcohols, esters, fatty acids, carbonyl compounds and hop oils in beer, and protein nitrogen by coomassie brilliant blue and total polyphenols in wort were compared before and after freezing the sample. It was found that most determinations were not affected by sample freezing, but the determinations of alcohol, original gravity and total polyphenols were affected. In case these very frequent determinations would need to be performed after freezing, a new uncertainty of the method was calculated for these analyzes. From the spectrum of fifteen tested carbonyl compounds, there was a statistically significant increase in the concentration of four compounds (2-methylpropanal, 2-methylbutanal, 3-methylbutanal, phenylacetaldehyde). A significant decrease after sample freezing was observed for most of the analyzed essential oils. [ABSTRACT FROM AUTHOR]

Point of care testing of residual effect of antiplatelet therapy in trauma patients or during major surgery may result in improved clinical management of significant bleeding. We included 121 healthy individuals (57 females and 64 males, aged 22–65 years) in order to establish reference intervals for platelet aggregation induced by adenosine diphosphate (ADPTEM, 10 µM), arachidonic acid (ARATEM, 0.42 mM) and thrombin activating peptide (TRAPTEM, 36 µM) employing the ROTEM platelet module. Further, the impact of citrate (3.2%) and hirudin (>15 µg/ml) as anticoagulants was evaluated. Finally, we investigated assay stability (15, 30, 60, and 120 min after blood sampling) (n = 8) and between-day variation (n = 5). We report reference intervals for 121 healthy individuals and reference intervals by gender. We observed significantly higher platelet aggregation in females than in males (all P-values < 0.05). No correlation between age and platelet aggregation was observed, except for the parameter TRAPTEM amplitude (A6), in which a decline in A6 was observed with increasing age (P = 0.03). We observed significantly lower levels of platelet aggregation in citrate tubes than in hirudin tubes (all P-values < 0.05), except from TRAPTEM maximum slope, where no significant difference was observed (P = 0.40). The stability was acceptable (≤20% deviation) for up to 120 min for ARATEM in citrate tubes, and up to 60 min for the ADPTEM and TRAPTEM assays in citrate tubes. In hirudin tubes we found ADPTEM and ARATEM assays to be stable for 60 min, while the stability of TRAPTEM in hirudin tubes was found to be stable for 30 min. Using citrate tubes, the between-day variation (mean coefficient of variation, CV) was 19–20% for ADPTEM, 19–26% for TRAPTEM, and 10% for ARATEM, whereas the mean CV was 11–13% for all three assays in hirudin tubes. In conclusion, we established combined and gender-specific reference intervals for three platelet aggregation assays in both citrate- and hirudin tubes. In citrate tubes, the stability of the ROTEM platelet assays was 60–120 min, while the stability in hirudin tubes was 30–60 min. The between-day variation was lowest for samples obtained in hirudin tubes. [ABSTRACT FROM AUTHOR]

As it is common practice for laboratories to store patient samples for a predefined period, allowing clinicians to request additional tests on previously collected samples, knowledge about sample stability is indispensable for the laboratorian. A common approach to estimating the maximum storage time is to use a discrete study design, measuring the analyte of interest at various time-points and then checking for significant differences with the help of a statistical test, such as Student's t-test, Wilcoxon's test or an analysis of variance (ANOVA) test. Because only discrete time intervals are considered, stability data can just be approximated. Alternatively, a continuous study design, as described by the Clinical and Laboratory Standards Institute (CLSI) for performing stability experiments for in vitro diagnostic reagents, can also be adopted by the clinical laboratory to evaluate the stability of biological samples. The major advantage of this approach is that it allows laboratories to define individual stability limits for different medical situations and offers more flexibility when choosing time-points for measurements. The intent of this paper is to demonstrate the evaluation of sample stability in the clinical laboratory with a continuous study design implemented with linear or non-linear regression analysis. Appropriate statistical modeling and acceptance criteria are presented, stability functions are described briefly, and checking the overall validity of the results is discussed. [ABSTRACT FROM AUTHOR]

Stability of a measurand in a specimen is a function of the property variation over time in specific storage conditions, which can be expressed as a stability equation, and is usually simplified to stability limits (SLs). Stability studies show differences or even inconsistent results due to the lack of standardized experimental designs and heterogeneity of the chosen specifications. Although guidelines for the validation of sample collection tubes have been published recently, the measurand stability evaluation is not addressed. This document provides an easy guideline for the development of a stability test protocol based on a two-step process. A preliminary test is proposed to evaluate the stability under laboratory habitual conditions. The loss of stability is assessed by comparing measurement values of two samples obtained from the same patient and analyzed at different time points. One of them is analyzed under optimal conditions (basal sample). The other is stored under specific stability conditions for a time set by the laboratory (test sample). Differences are expressed using percentage deviation (PD%) to facilitate comparison with specifications. When the preliminary test demonstrates instability, a comprehensive test is proposed in order to define the stability equation and to specify SLs. Several samples are collected from a set of patients. The basal sample is analyzed under optimal conditions, whereas analysis of test samples is delayed at time intervals. For each patient PD% is calculated as the difference between measurements for every test sample and its basal one and represented in a coordinate graph versus time. [ABSTRACT FROM AUTHOR]

In this study, the preservation of As(III) in model solutions and natural groundwater samples from four locations in Croatia was conducted. Model laboratory samples were spiked with As(III) and As(V), and different complexing agents. Solutions were analysed in intervals of 24, 48 h and during ten days after preparation. Model samples containing citric acid, sodium citrate, sodium oxalate and potassium sodium tartrate in combination with acetic acid, spiked with As(III)and As(V), showed good species preservation. As(III), in model samples, was preserved for 7 days with citric acid, and citric acid in combination with acetic acid, as well as with tartrate. As(III), in natural samples, was preserved for 6 to 12 days with potassium sodium tartrate, citric acid, and citric acid in combination with acetic acid and showed improvement, compared with unpreserved samples (oxidation in 3 days). The results showed that acetic acid alone was not successful in preserving As speciation. Good resolution of inorganic arsenic species was achieved using differential pulse anodic stripping voltammetry technique (DPASV). Since this technique is comparatively cheaper and more convenient to use than other available techniques it could become a method of choice for arsenic speciation in water.

Abstract Background Over the past couple of decades, measuring immunological parameters has become widespread in studies of ecology and evolution. A combination of different immunological indices is useful for quantifying different parts of the immune system and comprehensively assessing immune function. Running multiple immune assays usually requires samples to be repeatedly thawed and re-frozen. There is some evidence that repeated freezing and thawing can affect assay results, but this has never been comprehensively studied in some common ecological immunology assays. We tested the effect of multiple (1, 2, 3, 4, 5, 10) freeze-thaw cycles on the results of four commonly used immunological assays: haemolysis-haemagglutination titres, haptoglobin concentration, bacterial killing capacity and total immunoglobulins (IgY). We tested five different bird species from four different bird orders (Passeriformes, Columbiformes, Charadriiformes and Galliformes), and we included both captive and free-living individuals. In addition, we tested for haptoglobin concentrations and the haemolysis-haemagglutination assay if re-analysing samples 1 year apart led to different results. For the haemolysis-haemagglutination assay we also tested two different sources of rabbit blood, and we compared untreated microtitre plates with plates that were “blocked” to prevent nonspecific interactions between the plate and assay reagents. Results Repeated freezing and thawing of plasma had no effect on lysis titres, haptoglobin concentrations, bacterial killing capacity, or total immunoglobulin levels. Agglutination titres were unaffected by up to five cycles but were lower after ten freeze-thaw cycles. For the haemolysis-haemagglutination assay and haptoglobin concentrations, re-analysing samples 1 year apart yielded highly correlated data. For the haemolysis-haemagglutination assay, the source of rabbit blood did not influence the results, and the untreated vs. blocked plates differed slightly overall, but at the individual level assay results were highly correlated. Using different rabbit blood sources or different types of microtitre plates yielded highly correlated data. Conclusions Our data suggest that repeated freeze-thaw cycles do not impair assay results to the point of influencing ecological or evolutionary conclusions. Plasma samples can be safely stored in one tube and thawed repeatedly for different assays. Nevertheless, we recommend consistent treatment of samples in terms of freeze-thaw cycles or other laboratory treatments to minimize the potential for introducing a systematic bias.

Background: The addition of S100B protein to guidelines for the management of mild traumatic brain injury (mTBI) decreases the amount of unnecessary computed tomography (CT) scans with a significant decrease in radiation exposure and an increase in cost savings. Both DiaSorin and Roche Diagnostics have developed automated assays for S100B determination. Recently, bioMérieux developed a prototype immunoassay for serum S100B determination. For the first time, we present the evaluation of the S100B measurement using a bioMérieux Vidas® 3 analyzer. Methods: We evaluated the matrix effects of serum and plasma, and their stability after storage at 2–8 °C, −20 °C and −80 °C. The new measurement prototype (bioMérieux) was compared with an established one (Roche Diagnostics), and a precision study was also conducted. Lastly, clinical diagnostics performance of the bioMérieux and Roche Diagnostics methods were compared for 80 patients referred to the Emergency Department for mTBI. Results: Stability after storage at 2–8 °C, −20 °C, and −80 °C and validation of the serum matrix were demonstrated. The bioMérieux analyzer was compared to the Roche Diagnostics system, and the analytical precision was found to be efficient. Clinical diagnosis performance evaluation confirmed the predictive negative value of S100B in the management of mTBI. Conclusions: The study's data are useful for interpreting serum S100B results on a bioMérieux Vidas® 3 analyzer. [ABSTRACT FROM AUTHOR]

Aldosterone is produced by the adrenal gland and plays an important role in blood pressure regulation and electrolyte hemostasis. Clinically, measurement of urine aldosterone provides evidence for the diagnosis of hyper- and hypo-aldosteronism. Urine specimen that is collected in consecutive 24 h is preferred, which mitigates the risk of misdiagnosis due to large diurnal variation in aldosterone secretion. Preservatives such as boric acid are routinely added to the collection containers prior to urine collection. However, little is known of the effectiveness of these preservatives on stabilizing aldosterone in urine. In the current study, we examined the stability of urine aldosterone under typical clinical laboratory storage conditions with and without the supplementation of boric acid. Our result demonstrated that the addition of boric acid is unnecessary. • Preservatives are often required for 24 h urine collection to measure aldosterone. • The effectiveness of preservative such as boric acid to stabilize aldosterone in urine is not well understood. • Addition of boric acid as preservative to urine for aldosterone measurement is not needed based on our study results. [ABSTRACT FROM AUTHOR]

Background: The use of self-collected capillary blood has several advantages over phlebotomy, as such finger-prick testing is rapidly becoming accepted as a routine sample type for adults. However, there is limited evidence that venous and capillary serum is comparable for many analytes. This study aimed to determine whether capillary samples could offer an alternative sampling method to venous samples for the assessment of serum creatinine using the enzymatic method and if this analyte was stable in unspun capillary blood for 3 days. Methods: Matched capillary and venous blood samples were collected from 48 patients for the determination of serum creatinine, one set being processed on day zero, the other set being stored at ambient temperature and then processed on day three. Self-collected capillary blood was compared with phlebotomist-collected venous samples. Results: Serum creatinine concentrations from venous and capillary blood samples taken on day zero were compared to concentrations in capillary blood from day three. Data produced showed serum creatinine concentrations from capillary and venous serum to be comparable. Conclusion: It is believed that this is the first published study to determine if self-collected capillary blood sampling is an acceptable alternative to venous sampling for the measurement of serum creatinine concentration; our data indicates that there is no significant difference in results from unspun venous and capillary blood stored at room temperature for at least 3 days compared to venous blood tested on the same day of collection., Competing Interests: TW (Laboratory Director) was employed by Inuvi Diagnostics, ER (Laboratory Manager) was employed by Inuvi Diagnostics, MS (Clinical Innovation Lead) was employed by Thriva Ltd., (Copyright © 2023 Woolley, Rutter and Staudenmaier.)

There is scant documentation of the stability of common haematological parameters on storage of blood samples under tropical conditions. K2EDTA samples in multiple vials were taken from 20 healthy blood donors, baseline readings taken, and stored at 33°C and 37°C. Readings from the stored vials were taken after 1, 3 and 6 h. The percent change against the baseline readings at each time point for each storage temperature was calculated. Platelet counts showed an unacceptable shift within 1 h at 37°C and 3 h at 33°C; red cell volume related parameters showed an unacceptable shift within 3 h at 37°C and 6 h at 33°C. Haemoglobin, red blood cell count, white blood cell count and mean corpuscular haemoglobin remained stable for 6 h at both temperatures. The unacceptable change for many parameters on storage at ≥33°C demonstrates the importance of ensuring pre-analytical control in regions experiencing such climatic conditions. [ABSTRACT FROM AUTHOR]

Introduction: This study aimed to investigate the analytical bias in haematological parameters induced by storage at 33 °C. Materials and methods: Blood from the diversion pouch of 20 blood donors were collected in K2EDTA vials and stored at 33 °C. Readings from each vial were taken at 0, 4, 6, 12, 24, 48 and 72 hours after collection on the Sysmex XP-100 analyser (Sysmex Corporation, Kobe, Japan). The percent difference from the baseline readings were calculated and subjected to a Wilcoxon signed rank test at a Holm corrected significance level of 0.05. A median percent difference, which was statistically significant and greater than the maximum acceptable bias (taken from studies of biological variation), was taken as evidence of unacceptable shift. If the median shift was lesser than the maximum acceptable bias, two one-sided Wilcoxon signed rank tests for equivalence were used to determine whether the percent differences were significantly lesser than the maximum acceptable bias. Results: Haemoglobin, red blood cell count, white blood cell count, mean corpuscular haemoglobin and lymphocyte count showed acceptable bias after storage for at least 24 hours at 33 °C. Haematocrit, mean corpuscular volume, mean corpuscular haemoglobin concentration, platelet count and mean platelet volume showed unacceptable shift in less than 4 hours when stored at 33 °C. Conclusions: Since many haematological parameters show unacceptable bias within 4 hours of sample storage at 33 °C, the recommended limit of time from collection to processing should be revised for areas where high environmental temperatures are common. [ABSTRACT FROM AUTHOR]

Non-targeted metabolomics research of human volatile urinary metabolome can be used to identify potential biomarkers associated with the changes in metabolism related to various health disorders. To ensure reliable analysis of urinary volatile organic metabolites (VOMs) by gas chromatography-mass spectrometry (GC-MS), parameters affecting the headspace-solid phase microextraction (HS-SPME) procedure have been evaluated and optimized. The influence of incubation and extraction temperatures and times, coating fibre material and salt addition on SPME efficiency was investigated by multivariate optimization methods using reduced factorial and Doehlert matrix designs. The results showed optimum values for temperature to be 60 °C, extraction time 50 min, and incubation time 35 min. The proposed conditions were applied to investigate urine samples’ stability regarding different storage conditions and freeze-thaw processes. The sum of peak areas of urine samples stored at 4 °C, −20 °C, and −80 °C up to six months showed a time dependent decrease over time although storage at −80 °C resulted in a slight non-significant reduction comparing to the fresh sample. However, due to the volatile nature of the analysed compounds, more than two cycles of freezing/thawing of the sample stored for six months at −80 °C should be avoided whenever possible. [ABSTRACT FROM AUTHOR]

Background: Over the past couple of decades, measuring immunological parameters has become widespread in studies of ecology and evolution. A combination of different immunological indices is useful for quantifying different parts of the immune system and comprehensively assessing immune function. Running multiple immune assays usually requires samples to be repeatedly thawed and re-frozen. There is some evidence that repeated freezing and thawing can affect assay results, but this has never been comprehensively studied in some common ecological immunology assays. We tested the effect of multiple (1, 2, 3, 4, 5, 10) freeze-thaw cycles on the results of four commonly used immunological assays: haemolysis-haemagglutination titres, haptoglobin concentration, bacterial killing capacity and total immunoglobulins (IgY). We tested five different bird species from four different bird orders (Passeriformes, Columbiformes, Charadriiformes and Galliformes), and we included both captive and free-living individuals. In addition, we tested for haptoglobin concentrations and the haemolysis-haemagglutination assay if re-analysing samples 1 year apart led to different results. For the haemolysis-haemagglutination assay we also tested two different sources of rabbit blood, and we compared untreated microtitre plates with plates that were "blocked" to prevent nonspecific interactions between the plate and assay reagents. Results: Repeated freezing and thawing of plasma had no effect on lysis titres, haptoglobin concentrations, bacterial killing capacity, or total immunoglobulin levels. Agglutination titres were unaffected by up to five cycles but were lower after ten freeze-thaw cycles. For the haemolysis-haemagglutination assay and haptoglobin concentrations, re-analysing samples 1 year apart yielded highly correlated data. For the haemolysis-haemagglutination assay, the source of rabbit blood did not influence the results, and the untreated vs. blocked plates differed slightly overall, but at the individual level assay results were highly correlated. Using different rabbit blood sources or different types of microtitre plates yielded highly correlated data. Conclusions: Our data suggest that repeated freeze-thaw cycles do not impair assay results to the point of influencing ecological or evolutionary conclusions. Plasma samples can be safely stored in one tube and thawed repeatedly for different assays. Nevertheless, we recommend consistent treatment of samples in terms of freeze-thaw cycles or other laboratory treatments to minimize the potential for introducing a systematic bias. [ABSTRACT FROM AUTHOR]