Comparison of test results obtained from lithium heparin gel tubes and serum gel tubes

ObjectivesThere is currently trend that plasma might be alternative to serum due to some of its advantages. This study aimed to compare test results from heparinized plasma and serum.MethodsBlood samples from total of 40 participants (20 healthy, 20 hemodialysis patients) were drawn into serum gel tubes with clot activator and lithium heparin gel tubes. Twenty-eight clinical chemistry analytes were measured in serum and plasma samples. To determine whether difference between test results is clinically significant, total error (TE) was calculated and compared total allowable error (TEa) limits.ResultsTE of below 5% was calculated for amylase, AST, calcium, total cholesterol, chloride, CK, glucose, HDL-cholesterol, iron, LDH, LDL-cholesterol, magnesium, sodium, total bilirubin, uric acid and urea. Albumin, ALT, creatinine, CRP, lipase, phosphorus, potassium, total protein, and triglyceride had TE of 5–7%. TE of 7–10% were determined for ALP, direct bilirubin, and GGT. TE values were within TEa limits for all analytes.ConclusionsIt was concluded that results of 28 analytes measured in lithium heparin gel tubes are comparable to those of serum gel tubes. It is thought that several advantages including reduced turnaround time might be provided by using plasma instead of serum for these tests.

Simple thrombin-based method for eliminating fibrinogen interference in serum protein electrophoresis of haemodialysed patients

Introduction: Serum samples of haemodialysed patients collected through vascular access devices, e.g. central venous catheter (CVC) can contain residual heparin, which can cause incomplete clotting and consequently fibrinogen interference in serum protein electrophoresis (SPE). We hypothesized that this problem may be overcome by addition of thrombin and aimed to find a simple thrombin-based method for fibrinogen interference removal. Materials and methods: Blood samples of 51 haemodialysed patients with CVC were drawn through catheter into Clot Activator Tube (CAT) and Rapid Serum Tube Thrombin (RST) vacutainers (Becton Dickinson, New Jersey, USA) following the routine hospital protocols and analysed with gel-electrophoresis (Sebia, Lisses, France). Samples were redrawn in the CAT tubes and re-analysed after being treated with thrombin using two methods: transferring CAT serum into RST vacutainer and treatment of CAT serum with fibrinogen reagent (Multifibren U, Siemens, Marburg, Germany). Results: Direct blood collection in RST proved to be slightly more efficient than CAT in removing the interfering band in beta fraction (CAT removed 6/51 and RST removed 12/51, P = 0.031). Transferring CAT serum into the RST vacutainer proved to be more efficient for subsequent removal of interfering band from CAT serum than the addition of fibrinogen reagent (39/45 vs. 0/45 samples with efficiently removed interfering band, P < 0.001). Conclusion: Fibrinogen interference caused by incomplete clotting because of residual heparin can be overcome by addition of thrombin. Transferring CAT serum into the RST vacutainer was the most efficient method.

Çinko Düzeylerinin Ölçümünde Matriks Seçimi

INTRODUCTION: Measurement of blood zinc levels is frequently used in the diagnosis of a few conditions such as growth retardation, immunodeficiency, infertility, neurological disorder, and acrodermatitis enteropathica. The serum matrix is the most preferred one to determine zinc levels due to the ease of analysis with other tests and cost-effectiveness of blood collection tubes used to obtain serum samples. In our study, we aimed to compare serum and plasma zinc test results for accurate and reliable zinc measurement in plain tubes with clot activator and gel and in heparin-free tubes, which specifically produced for trace element analysis. METHODS: Twenty-seven randomly selected patients were included in the study. Blood samples drawn simultaneously from patients were pipetted into tubes with clot activator and gel (SST) (SST II Advance, Vacutainer, Becton Dickinson and Company, USA) as well as into trace element tubes with sodium heparin (NH) (NH Trace Elements Sodium Heparin, Vacuette, Greiner Bio-One GmbH, Austria). After the centrifugation process, zinc levels in serum and plasma samples were analyzed by colorimetric method using an autoanalyzer. Bias between serum and plasma zinc levels was evaluated according to the allowable bias criterion based on biological variation and regression analysis performed. RESULTS: The mean and standard deviation of serum and plasma zinc levels were 49.0±11.5 μg/dL and 46.4±12.0 μg/dL, respectively, and a statistically significant difference was determined (p=0.012) in between. Besides, the bias between serum and plasma was 6.8%, which was above the allowable bias (3.3%) and considered as clinically significant. No systematic or random errors detected. DISCUSSION AND CONCLUSION: When selecting a blood collection tube for trace element analysis, the structural differences between tubes and the matrix effect should be considered carefully.

Preanalytical stability of [-2]proPSA in whole blood stored at room temperature before separation of serum and plasma: implications to Phi determination

Background [-2]proPSA seems to outperform free/total prostate-specific antigen (PSA) ratio in prostate cancer diagnosis. However, [-2]proPSA stability remains an underestimated issue. We examined [-2]proPSA stability over time in whole blood before separation of serum and plasma and its implications for prostate health index (Phi) determination. Total PSA (tPSA) and free PSA (fPSA) stabilities were also assessed. Methods Blood was drawn from 26 patients and separated in two tubes for plasma (K2EDTA and K2EDTA plus protease inhibitors – P100) and one for serum (clot activator plus gel separator). Tubes were stored at room temperature before centrifugation 1, 3 and 5 h for serum and EDTA plasma or 1 and 5 h for P100 plasma. To investigate the influence of gel separator on markers’ stability, blood was collected from 10 patients in three types of tubes to obtain serum: tubes with clot activator plus gel separator, with silica particles or glass tubes. Biomarkers were assayed with chemiluminescent immunoassays. Results [-2]proPSA and Phi levels significantly and progressively increased over time in serum (+4.81% and +8.2% at 3 h; +12.03% and +14.91% at 5 h, respectively, vs. 1 h; p<0.001). Conversely, [-2]proPSA levels did not change in plasma (EDTA or P100). tPSA levels did not change over time in serum or plasma, whereas fPSA decreased in serum. All markers were higher in plasma than in serum at any time point. This difference did not seem to be attributable to the use of gel for serum preparation. Conclusions EDTA prevented spurious in vitro modifications in PSA-related isoforms, confirming that a stabilized blood sample is a prerequisite for [-2]proPSA measurement and Phi determination.

A comparative evaluation of lithium estimation for samples collected in different tubes and its stability on storage

PURPOSE: Lithium (Li) is a well-established drug for the treatment of bipolar affective disorders. Li as a drug is known to possess a narrow therapeutic index. Thus, regular monitoring of blood Li in patients receiving Li therapy is essential. Plain tubes with clot activator are known to interfere with Li estimation. The current study was planned to compare Li estimation in sera from vacutainers with clot activator, and plasma from sodium heparinized vacutainers with that of Li estimation in sera from glass vials. The time-dependant stability of Li estimation on storage at 2°C–8°C for 48 h in these three set of tubes was also evaluated. MATERIALS AND METHODS: Blood from the patients on Li therapy (n = 100) was collected in 3 different collection tubes: plain vacutainer with clot activator (S), Sodium heparinized vacutainer (P) and Glass vial (G) and was analyzed by ion selective electrode (ISE) analyzer for Li levels. Secondary aliquots were also taken from each type of collection tube and stored at 2°C–8°C. Time-dependant stability of Li estimation was checked at 12 h, 24 h, and 48 h. ANOVA followed by Tukey's posttest was performed to calculate statistical significance taking glass vial as reference collection tube. Bland–Altman plots were plotted to compare between three collection tubes at baseline. Stability on storage was defined when >95% of the samples were within allowable error limit for that time point taking baseline levels as reference. RESULTS: A mean bias of 0.18 mmol/L and mean percentage bias of 19.9% in Li levels was observed between serum from (S) than serum from (G). This difference was found to be statistically significant. However, statistically nonsignificant mean bias of 0.02 mmol/L and mean percentage bias of 3.34% in Li levels was observed between plasma from (P) and serum from (G). Time-dependant stability was observed more in glass vials as compared to vacutainers with clot activator or sodium heparin. CONCLUSION: Serum from glass vial should be the preferred method for blood collection to determine Li levels.

Interference in Serum Lithium Estimation by Silica Clot Activator and Silicone Surfactant in ISE Principle: a Cross-Sectional Study

Serum lithium concentration is monitored to ensure patient's compliance and to avoid intoxication and thus it is a prerequisite for an individual's dose adjustment. An unavoidable error during lithium estimation in blood collected in 'red-top plastic vacutainer plus tube containing silica clot activator and silicone surfactant' by ISE appeared as a reality for a standard laboratory like AFIP. The error could not be detected even by proven internal and external QC. This cross-sectional study was carried out at AFIP Chemical Pathology Department from May' 2015 to July'2015 to find out the interference causing falsely elevated serum lithium concentration by ISE principle. Blood were collected from the 40 study subjects including 30 healthy volunteers, who never took Tab Lithium and 10 patients, who used to take Tab Lithium for bipolar mood disorder in both 'plain red-top plastic vacutainer tubes without additive' as well as 'plain red-top plastic vacutainer plus tube containing silica clot activator and silicone surfactant'. Lithium concentrations were estimated in both types of tubes by Ion-Selective Electrode (ISE) principle employing world class, USA manufactured analyzer NOVA-4 as well as by colorimetric method using Dade Dimension, Siemens. Serum lithium concentrations were undetectable for the 'lithium-free normal volunteers' in both types of tubes measured by colorimetry but in ISE principle it was undetectable when collected in plain test tube without additives but when collected in 'vacutainer plus tube containing silica clot activator and silicone surfactant' and measured by ISE technique, the mean serum lithium concentration was found to be 1.78 ±0.40 mmol/l. Besides, mean serum lithium concentration of 10 individuals taking Tab Lithium had no statistically significant difference while measured by ISE or colorimetry in 'vacutainer tubes without additive' and also in 'vacutainer plus tubes containing silica clot activator and silicone surfactant' measured by colorimetry. But, vacutainer plus tubes containing silica clot activator and silicone surfactant' while measured serum lithium concentration by ISE principle had significant (p <0.001) increase in mean concentration than others, as determined by one-way ANOVA and Post-hoc tests. This study demonstrates that positive interference; caused by silica clot activator and silicone surfactant of the collection tubes; increases measured concentration of lithium. This interference; being in the pre-analytic phase, cannot be detected by routinely performed laboratory quality control.Bangladesh J Med Biochem 2015; 8(2): 60-65

Heparinate but not serum tubes are susceptible to hemolysis by pneumatic tube transportation

Background:Pneumatic tube transportation (PTT) may induce hemolysis (H) in blood samples. We aimed to compare the H degree before and after PTT implementation in our hospital.Methods:Hemolysis indices (HI) for all lithium-heparin plasma samples (P) drawn by the Emergency Department in 2-month periods were retrospectively collected and pre- (n=3579) and post-PTT (n=3469) results compared. The impact of PTT introduction was investigated on LDH [HI threshold (HIt), 25], conjugated bilirubin (cBIL) (HIt, 30), K (HIt, 100) and ALT (HIt, 125). In addition, HI retrieved for P and paired serum samples collected in silica clot activator tubes (S) from the same venipuncture were compared in pre- (n=501) and post-PTT (n=509) periods.Results:Median (5–95th percentile) HI in P was significantly higher in post-PTT period [7 (0–112) vs. 6 (0–82), p<0.001]. Results reported as ‘Hemolysis’ in P increased from 6.6% in pre-PTT to 9.4% in post-PTT (p<0.001). Investigated tests gave the following rejection rates (pre-PTT vs. post-PTT): LDH, 13.4% vs. 18.8%, p<0.001; cBIL, 9.4% vs. 27.0%, p<0.05; K, 3.7% vs. 5.6%, p<0.001; ALT, 2.9% vs. 4.4%, p<0.01. The slightly higher susceptibility to H of S compared to paired P found in the pre-PTT [9 (1–64) vs. 6 (0–85)] was not confirmed in the post-PTT period [7 (0–90) vs. 8 (1–72)], in which median HI in S was significantly lower (p<0.001) than in pre-PTT.Conclusions:In our setting PTT promotes H in P, increasing the rate of rejected tests. The use of S appears to protect against the hemolysing effect of PTT.

Comparison of Improvacuter™ tubes with BD Vacutainer™ tubes for various hormones in the aspects of stability and influence of gel separators

Validation of blood collection tubes are important to determine the role of different collection tubes which influence the assurance of laboratory results. We compared two different tubes (ImprovacuterWe compared the results of nine immunoassays performed on UniCelEstradiol and testosterone concentrations obtained from Improvacuter Gel and Clot Activator tubes and BD Vacutainer SST II Advance tubes remained below the lower limits of analytical range for the same analytes while they were within the limits in BD Vacutainer Clot Activator tubes and Improvacuter tubes. Statistical significance of stability was not clinically significant for the hormone parameters we tested in all four tubes.Gel containing tubes (both BD and Improve) gave comparable results with the tubes which do not contain gel except for estradiol and testosterone. The use of gel containing tubes for estradiol and testosterone are not recommended on UniCel