Blood Stored In EDTA Tubes Provides Accurate Peanut Basophil Activation Test Results For 48 hours.

BACKGROUND: The peanut basophil activation test (BAT) has demonstrated excellent diagnostic accuracy with heparinized blood, but its clinical utility is limited by the short stability of samples stored in this anticoagulant. OBJECTIVE: Using EDTA anticoagulated blood, these investigations determined if Peanut BAT sample stability can be extended to 2 days, the minimum stability requirement for diagnostic tests currently offered through American reference laboratories. METHODS: Peanut non-allergic control (NAC), peanut IgE sensitized (PS), and peanut allergic (PA) children aged 6 months through 17 years were recruited from members of Kaiser Permanente Southern California. EDTA anti-coagulated blood samples were collected from participants, shipped to a centralized laboratory, and stored at 4oC for peanut BAT testing 1 and 2 days later. RESULTS: Peanut BAT results for 23 unblinded participants were used to establish sample rejection and interpretation criteria that were subsequently validated in a prospective double-blind study involving 112 additional children (39-NAC, 36-PS, 37-PA). Of 105 blinded blood samples tested on each study day, 88 (84%) day-1 and 90 (86%) day-2 peanut BAT results were considered interpretable, with diagnostic accuracies of 95.5% and 94.4%, respectively. Moreover, all interpretable PA results were considered positive (100% sensitivity). CONCLUSION: Using EDTA anti-coagulated blood samples collected remotely, 1 and 2 days before testing, study results highlight the favorable diagnostic performance characteristics of the peanut BAT and provide further evidence that the test could be readily operationalized for clinical use by interested commercial reference laboratories.

Optimizing d-mannose and glyceraldehyde concentrations as glucose preservatives without clinically affecting biochemical test results.

Objectives: The objectives were to evaluate blood additives that combined lithium heparin (LH)-salt with glyceraldehyde (GLY) or d-mannose (MAN) for preserving glucose levels in plasma samples and to simultaneously determine the compatibility of these additives with 14 other biochemical tests. Methods: Blood samples from 40 subjects, equally divided into healthy and diabetic groups, were collected using five different additives. The three most effective additives, LH/GLY, LH/MAN, and LH/GLY/MAN, were selected for ensuring the best preservation of glucose levels and compatibility with 14 biochemical tests. One-way analysis of variance was used to analyze the mean paired differences of glucose level and biochemical tests. Simultaneously, the clinical criteria from Johns Hopkins Hospital were used to guide the interpretation and set acceptable thresholds for measurements that exceeded the standards. Results: The combination of 160 mmol/L GLY, 8.4 mmol/L MAN, and LH, maintained glucose levels at approximately 93.4-93.7 % for healthy subjects and 91.3-92.8% for subjects with diabetes mellitus over 8 h. The mean paired differences of glucose levels in preservation were statistically insignificant. The biases in 14 biochemical tests for LH/GLY/MAN and LH/MAN remained within the acceptable clinical criteria during the 8 h. Conclusions: Combining 160 mmol/L GLY, 8.4 mmol/L MAN, and LH, proved more effective in maintaining glucose levels than individual additives or the conventional sodium fluoride preservative. It did not yield clinical discrepancies in the 14 biochemical tests during 8 h at room temperature.

Quality assurance of add-on testing in plasma samples: stability limit for 29 biochemical analytes.

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.

Possible alternative strategies to implement basophil activation testing in multicentric studies.

The Basophil Activation Test (BAT) enables flow cytometry characterization of basophil reactivity against specific allergenic molecules. The focus now revolves around democratizing this tool, but, as blood sample stability could be challenging, after having developed a simplified approach, herein, we aimed to characterize two strategies for implementing BAT in multicentric studies: store and ship blood before or after sample processing. Fresh heparin- and EDTA-anticoagulated whole blood samples followed both BAT workflows: "collect, store, process & analyze" or "collect, process, store & analyze". Storage temperatures of 18-25 °C or 2-8 °C and preservation times from 0 to 7 days were considered. Interleukin-3 was also evaluated. With the "collect, store, process & analyze" workflow, heparin-anticoagulated blood and 18-25 °C storage were better than other conditions. While remaining possible, basophil activation exhibited a possible reactivity decay after 24 h. Under the conditions tested, interleukin-3 had no role in enhancing basophil reactivity after storage. Conversely, the "collect, process, store & analyze" workflow demonstrated that either heparin- or EDTA-anticoagulated blood can be processed and kept up to 7 days at 18-25 °C or 2-8 °C before being analyzed. Various strategies can be implemented to integrate BAT in multicentric studies. The "collect, store, process & analyze" workflow remains a simplified logistical approach, but depending on time required to ship from the clinical centers to the reference laboratories, it might not be applicable, or should be used with caution. The "collect, process, store & analyze" workflow may constitute a workflow improvement to provide significant flexibility without impact on basophil reactivity.

SARS-CoV-2 live virus culture and sample freeze-thaw stability.

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.

ALISTER - Application for lipid stability evaluation and research.

BACKGROUND AND AIMS: In lipidomic and metabolomic studies, pre-analytical pitfalls enhance the risk of misusing resources such as time and money, as samples that are analyzed may not yield accurate or reliable data due to poor sample handling. Guidance and pre-analytic know-how are necessary for translation of omics technologies into routine clinical testing. The present work aims to enable decision making regarding sample stability in every phase of lipidomics- and metabolomics-centered studies. MATERIALS AND METHODS: Data of multiple pre-analytic studies were aggregated into a database. Flexible approaches for evaluating these data were implemented in an RShiny-based web-application, tailored towards broad applicability in clinical and bioanalytic research. RESULTS: Our "Application for lipid stability evaluation & research" - ALISTER facilitates decision making on blood sample stability during lipidomic and metabolomic studies, such as biomarker research, analysis of biobank samples and clinical testing. The interactive tool gives sampling recommendations when planning sample collection or aids in the assessment of sample quality of experiments retrospectively. CONCLUSION: ALISTER is available for use under https://itmp.shinyapps.io/alister/. The application enables and simplifies data-driven decision making concerning pre-analytic blood sample handling and fits the needs of clinical investigations from multiple perspectives.

Sample Preparation for Electron Cryo-Microscopy of Macromolecular Machines.

High-resolution structure determination by electron cryo-microscopy underwent a step change in recent years. This now allows study of challenging samples which previously were inaccessible for structure determination, including membrane proteins. These developments shift the focus in the field to the next bottlenecks which are high-quality sample preparations. While the amounts of sample required for cryo-EM are relatively small, sample quality is the key challenge. Sample quality is influenced by the stability of complexes which depends on buffer composition, inherent flexibility of the sample, and the method of solubilization from the membrane for membrane proteins. It further depends on the choice of sample support, grid pre-treatment and cryo-grid freezing protocol. Here, we discuss various widely applicable approaches to improve sample quality for structural analysis by cryo-EM.

Acceptability of plasma ammonia results when samples are not transported and processed under ideal conditions.

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.

The impact of cryoprotectant exposure time on post-thaw viability of autologous and allogeneic hematopoietic stem cells and leukocyte subpopulations.

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. Analysis of the absolute count of viable cells in thawed samples showed a significant difference between all measurement points for CD34+ (p < 0.001), CD14+ (p < 0.001), and CD19+ cells (p < 0.001). No significant differences were observed for post-thaw stability of allogeneic samples analysed between products stored before cryopreservation ≥ 24 hours (N = 20), and those stored < 24 hours (N = 10), except for viable CD3+/CD4+ cells after three hours post-thaw (p = 0.028). In conclusion, DMSO had different effects on leukocyte subpopulations in cryopre-served PBSC samples. The type of donors and the length of storage before cryopreservation did not affect the post-thaw stability of cryopreserved PBSC samples.

Comparability and Stability of Serum Creatinine Concentration in Capillary and Venous Blood.

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.

The stability of C-peptide and insulin in plasma and serum samples under different storage conditions.

OBJECTIVES: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.

Recommendation for the design of stability studies on clinical specimens.

OBJECTIVES: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.

Sample stability and heparin interference in ionized calcium and ionized magnesium measurements in horses using the Stat Profile Prime Plus co-oximetry electrolyte analyzer.

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.

Evaluation of the stability of fecal immunochemical test specimens.

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.

Evaluation of the impact of pre-analytical conditions on sample stability for the detection of SARS-CoV-2 RNA.

Demand for accurate SARS-CoV-2 diagnostics is high. Most samples in the UK are collected in the community and rely on the postal service for delivery to the laboratories. The current recommendation remains that swabs should be collected in Viral Transport Media (VTM) and transported with a cold chain to the laboratory for RNA extraction and RT-qPCR. This is not always possible. We aimed to test the stability of SARS-CoV-2 RNA subjected to different pre-analytical conditions. Swabs were dipped into PBS containing cultured SARS-CoV-2 and placed in either a dry tube or a tube containing either normal saline or VTM. The tubes were then stored at different temperatures (20-50 °C) for variable periods (8 h to 5 days). Samples were tested by RT-qPCR targeting SARS-CoV-2 E gene. VTM outperformed swabs in saline and dry swabs in all conditions. Samples in VTM were stable, independent of a cold chain, for 5 days, with a maximum increase in cycle threshold (Ct) of 1.34 when held at 40 °C. Using normal saline as the transport media resulted in a loss of sensitivity (increased Ct) over time and with increasing temperature (up to 7.8 cycles compared to VTM). SARS-CoV-2 was not detected in 3/9 samples in normal saline when tested after 120 h incubation. Transportation of samples in VTM provides a high level of confidence in the results despite the potential for considerable, uncontrolled variation in temperature and longer transportation periods. False negative results may be seen after 96 h in saline and viral loads will appear lower.

Transport stability profiling - a proposed generic protocol.

OBJECTIVES: Diagnostic samples are exposed to a spectrum of variables during transport to laboratories; therefore, the evaluation of a rather comprehensive stability profile of measurands is warranted. While appropriate testing standards have been established for pharmaceuticals and reagents, this is not the case for diagnostic samples. The aim of our work was to develop and evaluate a protocol applicable to diagnostic samples. METHODS: An isochronous approach with representation of temperature and exposure duration in a two-dimensional matrix was established. The deviations of the measurement results from the baseline associated with the exposure are evaluated with respect to the measurement uncertainty of the analytical measurement procedure applied. Variables of the experiment are documented in a standardized matrix. As a proof-of-concept, we profiled the stability patterns of a number of measurands at four temperature levels over up to 72 h in primary serum sample tubes. RESULTS: The protocol proved to be workable and allowed the description of a comprehensive stability profile of a considerable number of compounds based on 21 small-volume primary samples collected from each volunteer and exposed according to this protocol. CONCLUSIONS: A straightforward and feasible isochronous protocol can be used to investigate in detail the effects of different pre-processing conditions on the stability of measurands in primary samples during transport to diagnostic laboratories. This is of significance as pre-analytical logistics become increasingly important with the centralization of analytical services.

Automated data analytics workflow for stability experiments based on regression analysis.

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.

Stability of Wheat Floret Metabolites during Untargeted Metabolomics Studies.

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.

Stability of Glucose Concentrations in Frozen Plasma.

BACKGROUND: Conflicting information is available regarding the stability of glucose concentrations in frozen plasma samples. Clinical trials could benefit from such long-term storage because it would allow usage of a central laboratory with higher-quality laboratory analyzers in contrast to mobile analyzers in a decentralized setting. METHODS: In this study, venous blood samples were collected in lithium-heparin gel tubes. Plasma was separated immediately after blood was drawn, and from each of the 21 plasma samples, 6 aliquots were prepared for measurement at 6 time points: immediately and after 2, 4, 6, 8, and 12 weeks. Between sampling and measurement, aliquots were stored at less than -20°C. Transport on dry ice was simulated by placing aliquots in a -80°C freezer for 5 days between weeks 8 and 12. Measurements were performed on a hexokinase-based laboratory analyzer.Average relative differences and corresponding 99% confidence intervals (CIs) were calculated between the stored aliquots' and the immediately measured aliquots' glucose concentrations. Glucose concentrations were deemed stable as long as average relative differences were ≤±2.5%. RESULTS: Over the whole 12-weeks duration, the largest average relative difference was -1.82% (99% CI: -2.25% to -1.39%). Shorter storage durations tended to lead to less bias. CONCLUSION: In this study, the stability of glucose concentrations in frozen plasma samples obtained with lithium-heparin gel tubes could be shown for up to 12 weeks. Future studies should be performed to assess whether this is independent of the glucose analyzer and the type of sampling tube used.