Thrombin-accelerated quick clotting serum tubes: an evaluation with 22 common biochemical analytes

Serum bicarbonate stability study at room temperature - influence of time to centrifugation and air exposure on bicarbonate measurement reported according to the CRESS checklist

OBJECTIVES

The aim was to evaluate the stability of serum bicarbonate at room temperature, depending on time to centrifugation and air exposure.

METHODS

Stability study was conducted in the laboratory of Clinical Hospital Centre Rijeka, Croatia in January-February 2022. Nine samples from 10 volunteers were collected in clot activator gel tubes (Greiner Bio-One). Bicarbonate was measured on Beckman Coulter AU480 (Beckman Coulter, Brea, USA). Three tubes were left at room temperature for 30 min, three tubes for 2 h, three tubes for 4 h until centrifugation. First tube from first group (baseline) was measured immediately after centrifugation. Other measurements were expressed as percentage deviation (PD%) from baseline. First tube was remeasured after 1 and 2 h (OT_0h_1h; OT_0h_2h). Second and third tubes were opened 1 and 2 h after centrifugation (C_0h_1h; C_0h_2h). Second group of tubes was processed the same way with 2-hour centrifugation delay (WB_2h; OT_2h_1h; OT_2h_2h; C_2h_1h; C_2h_2h), and third group with 4-hour delay (WB_4h; OT_4h_1h; OT_4h_2h; C_4h_1h; C_4h_2h). PD% was compared to Maximum Permissible Difference (MPD=5.69%). MedCalc statistical software was used (MedCalc, Ostend, Belgium).

RESULTS

Bicarbonate baseline mean value (range) was 27.3 (23.4-29.6) mmol/L. Obtained PD% (95%CI) were: C_0h_1h 0.46 (-1.21, 2.12); C_0h_2h 0.18 (-2.22, 2.57); OT_0h_1h -6.46 (-7.57, -5.36); OT_0h_2h -10.67 (-12.13, -9.21); WB_2h -0.15 (-2.04, 1.74); C_2h_1h 0.01 (-1.52, 1.54); C_2h_2h -0.40 (-2.65, 1.85); OT_2h_1h -5.43 (-7.30, -3.55); OT_2h_2h -11.32 (-13.57, -9.07); WB_4h -0.85 (-3.28, 1.58); C_4h_1h -2.52 (-4.93, 0.11); C_4h_2h -3.02 (-5.62, 0.43); OT_4h_1h -7.34 (-9.64, -5.05); OT_4h_2h -11.85 (-14.38, -9.33).

CONCLUSIONS

Serum bicarbonate is stable for 4 h in closed uncentrifuged tubes, another 2 h in closed tubes after centrifugation, and is unstable within 1 h in opened tube.

Evaluation of the quick-clotting serum separator tube, VQ-Tube™, for clinical chemistry and thyroid hormone assays

BACKGROUND

The type of blood collection tube affects specimen quality and laboratory results. Because plasma specimens have a shorter processing time compared with serum specimens, emergency biochemistry tests use plasma. However, serum specimens remain stable after centrifugation and show more accurate results than plasma. Therefore, a quick-clotting serum separator tube is expected to be useful for shorter turnaround times and accurate results. We evaluated a new quick-clotting serum separator tube VQ-Tube™ (AB Medical, Korea) for clinical chemistry and thyroid hormone assays.

METHODS

One hundred volunteers from four university hospitals were recruited, and peripheral blood samples were collected in quick-clotting serum separator tube VQ-Tubes™ and the commonly used serum separator tube V-Tubes™. The obtained specimens were used for 16 clinical chemistry assays and three thyroid hormone assays.

RESULTS

The differences (%) in the test results obtained from the samples in each tube satisfied the allowable difference ranges (19 assays). The differences in the test results between the tubes satisfied the desired specifications for accuracy except for the glucose results (2.75%). The paired t-test revealed significant differences between the results of six assays, but each set of results showed a good correlation. Samples were visually inspected for serum clarity and gel barrier integrity, and incomplete clotting reactions and haemolysed serum were not observed.

CONCLUSIONS

The new quick-clotting VQ-Tube™ demonstrated reliable test results compared with the commonly used serum separator tube V-Tube™. This quick-clotting tube will provide fast test results with adequately separated serum specimens, especially for patients who need fast tests.

A Review of Efforts to Improve Lipid Stability during Sample Preparation and Standardization Efforts to Ensure Accuracy in the Reporting of Lipid Measurements

Lipidomics is a rapidly growing field, fueled by developments in analytical instrumentation and bioinformatics. To date, most researchers and industries have employed their own lipidomics workflows without a consensus on best practices. Without a community-wide consensus on best practices for the prevention of lipid degradation and transformations through sample collection and analysis, it is difficult to assess the quality of lipidomics data and hence trust results. Clinical studies often rely on samples being stored for weeks or months until they are analyzed, but inappropriate sampling techniques, storage temperatures, and analytical protocols can result in the degradation of complex lipids and the generation of oxidized or hydrolyzed metabolite artifacts. While best practices for lipid stability are sample dependent, it is generally recommended that strategies during sample preparation capable of quenching enzymatic activity and preventing oxidation should be considered. In addition, after sample preparation, lipid extracts should be stored in organic solvents with antioxidants at -20 °C or lower in an airtight container without exposure to light or oxygen. This will reduce or eliminate sublimation, and chemically and physically induced molecular transformations such as oxidation, enzymatic transformation, and photon/heat-induced degradation. This review explores the available literature on lipid stability, with a particular focus on human health and/or clinical lipidomic applications. Specifically, this includes a description of known mechanisms of lipid degradation, strategies, and considerations for lipid storage, as well as current efforts for standardization and quality insurance of protocols.

Rapid serum tube technology overcomes problems associated with use of anticoagulants

Introduction

Failure to obtain complete blood clotting in serum is a common laboratory problem. Our aim was to determine whether snake proth-rombin activators are effective in clotting blood and producing quality serum for analyte measurement in anticoagulated patients.

Materials and methods

Whole blood clotting was studied in a total of 64 blood samples (41 controls, 20 Warfarin patients, 3 anticoagulated patients using snake venom prothrombin activator (OsPA)) with plain tubes. Coagulation was analysed using a visual assay, Hyland-Clotek and thromboelastography. Healthy control blood was spiked with a range of anticoagulants to determine the effectiveness of OsPa-induced clotting. A paired analysis of a Dabigatran patient and a control investigated the effectiveness of the OsPA clotting tubes. Biochemical analytes (N = 31) were determined for 7 samples on chemistry and immunoassay analysers and compared with commercial tubes.

Results

Snake venom prothrombin activators efficiently coagulated blood and plasma spiked with heparin and commonly used anticoagulants. Clotting was observed in the presence of anticoagulants whereas no clotting was observed in BDRST tubes containing 3 U/mL of heparin. Snake venom prothrombin activator enhanced heparinised blood clotting by shortening substantially the clotting time and improving significantly the strength of the clot. Comparison of 31 analytes from the blood of five healthy and two anticoagulated participants gave very good agreement between the analyte concentrations determined.

Conclusions

Our results showed that the snake venom prothrombin activators OsPA and PtPA efficiently coagulated recalcified and fresh bloods with or without added anticoagulants. These procoagulants produced high quality serum for accurate analyte measurement.

Exogenous sample contamination. Sources and interference

Clinical laboratory medicine is involved in the vast majority of patient care pathways. It has been estimated that pathology results inform 60-70% of critical patient care decisions. The primary goal of the laboratory is to produce precise and accurate results which reflect the true situation in vivo. It is not surprising that interference occurs in laboratory analysis given the complexity of some of the assays used to perform them. Interference is defined as "the effect of a substance upon any step in the determination of the concentration or catalytic activity of the metabolite". Exogenous interferences are defined as those that derive from outside of the body and are therefore not normally found in a specimen and can cause either a positive or negative bias in analytical results. Interferences in analysis can come from various sources and can be classified as endogenous or exogenous. Exogenous substances could be introduced at any point in the sample journey. The laboratory must take responsibility for the quality of results produced. It has a responsibility to have processes in place to identify and minimise the occurrence and effect contamination and interference. To do this well the laboratory needs to work with clinicians and manufacturers. Failure to identify an erroneous result could have an impact on patient care, patient safety and also on hospital budgets. However it is not always easy to recognise interferences. This review summarises the types and sources of exogenous interference and some steps to minimise the impact they have.

Evaluation of the BD Vacutainer(®) RST blood collection tube for routine chemistry analytes: clinical significance of differences and stability study

Introduction:

Preanalytical variables account for most of laboratory errors. There is a wide range of factors that affect the reliability of laboratory report. Most convenient sample type for routine laboratory analysis is serum. BD Vacutainer^® Rapid Serum Tube (RST) (Becton, Dickinson and Company, Franklin Lakes, NJ, USA) blood collection tube provides rapid clotting time allowing fast serum separation. Our aim was to evaluate the comparability of routine chemistry parameters in BD Vacutainer^® RST blood collection tube in reference with the BD Vacutainer^® Serum Separating Tubes II Advance Tube (SST) (Becton, Dickinson and Company, Franklin Lakes, NJ, USA).

Materials and methods:

Blood specimens were collected from 90 participants for evaluation on its results, clotting time and stability study of six routine biochemistry parameters: glucose (Glu), aspartate aminotransferase (AST), alanine aminotransferase (ALT), calcium (Ca), lactate dehidrogenase (LD) and potassium (K) measured with Olympus AU2700 analyzer (Beckman Coulter, Tokyo, Japan). The significance of the differences between samples was assessed by paired t-test or Wilcoxon Matched-Pairs Rank test after checking for normality.

Results:

Clotting process was significantly shorter in the RSTs compared to SSTs (2.49 min vs. 19.47 min, respectively; P < 0.001). There was a statistically significant difference between the RST and SST II tubes for glucose, calcium and LD (P < 0.001). Differences for glucose and LD were also clinically significant. Analyte stability studies showed that all analytes were stable for 24 h at 4 °C.

Conclusions:

Most results (except LD and glucose) from RST are comparable with those from SST. In addition, RST tube provides shorter clotting time.

Thrombin-mediated degradation of parathyroid hormone in serum tubes

BACKGROUND

Intact parathyroid hormone (PTH) tests are frequently sandwich immunoassays. Enzymes that cleave PTH may cause falsely lower PTH results. The objective of this study was to determine whether bovine thrombin in Becton Dickinson (BD) Vacutainer rapid serum tubes™ (RSTs) may lead to PTH results that are lower than in plasma separator tube™ (PST) or serum separator tube™ (SST) collections.

METHODS

Tubes of blood (PST, SST, and RST) were collected from donors. PTH concentrations were measured on a Roche Cobas e602 analyzer in aliquots held at room temperature or 4°C across time. Instrument comparison studies were also conducted on an Abbott Architect i1000SR and a Siemens Immulite 2000 XPi. Previously collected serum specimens were also incubated in exogenous bovine thrombin, the direct thrombin inhibitor hirudin, or both. Freshly collected RST specimens were also spiked with hirudin after clotting and centrifugation.

RESULTS

Significant decreases in PTH degradation rate constants were observed according to tube type, with degradation rates faster in RSTs than SSTs, and SSTs faster than PSTs. PTH degradation rate was temperature dependent. PTH decreases induced by exogenous bovine thrombin, as well as endogenous human thrombin, were reduced by hirudin.

CONCLUSIONS

Bovine thrombin is responsible for the decrease in PTH results observed in RSTs. Endogenous human thrombin, activated during clot formation, is likely responsible for the smaller decreases observed in non-RST sera versus plasma.

Interferences from blood collection tube components on clinical chemistry assays

Improper design or use of blood collection devices can adversely affect the accuracy of laboratory test results. Vascular access devices, such as catheters and needles, exert shear forces during blood flow, which creates a predisposition to cell lysis. Components from blood collection tubes, such as stoppers, lubricants, surfactants, and separator gels, can leach into specimens and/or adsorb analytes from a specimen; special tube additives may also alter analyte stability. Because of these interactions with blood specimens, blood collection devices are a potential source of pre-analytical error in laboratory testing. Accurate laboratory testing requires an understanding of the complex interactions between collection devices and blood specimens. Manufacturers, vendors, and clinical laboratorians must consider the pre-analytical challenges in laboratory testing. Although other authors have described the effects of endogenous substances on clinical assay results, the effects/impact of blood collection tube additives and components have not been well systematically described or explained. This review aims to identify and describe blood collection tube additives and their components and the strategies used to minimize their effects on clinical chemistry assays.