Comparison of BD Vacutainer SST™ Plus Tubes with BD SST™ II Plus Tubes for common analytes PDF

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Clinica Chimica Acta 306 Ž2001. 139–143 www.elsevier.comrlocaterclinchim Short communication Comparison of BD Vacutainer SSTe Plus Tubes with BD SSTe II Plus Tubes for common analytes Valerie J. Bush a,) , Margaret R. Janu b, Franz Bathur b, Alice Wells c , Amitava Dasgupta c a Becton Dickinson and ...

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Comparison of BD Vacutainer SST™ Plus Tubes with BD SST™ II Plus Tubes for common analytes Margaret R Janu Clinica Chimica Acta

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Clinica Chimica Acta 306 Ž2001. 139–143 www.elsevier.comrlocaterclinchim

Short communication

Comparison of BD Vacutainer SSTe Plus Tubes with BD SSTe II Plus Tubes for common analytes Valerie J. Bush a,) , Margaret R. Janu b, Franz Bathur b, Alice Wells c , Amitava Dasgupta c a

Becton Dickinson and Company, 1 Becton DriÕe, MC 307, Franklin Lakes, NJ 07417-1885, USA Pathology Department, Concord Repatriation General Hospital , Hospital Road, Concord, NSW 2137, Australia Department of Pathology and Laboratory Medicine, UniÕersity of Texas-Houston Medical School, 6431 Fannin, MSB 2.292, Houston, TX 77030, USA b

c

Received 11 October 2000; received in revised form 27 December 2000; accepted 16 January 2001

Abstract Serum separator tubes were introduced 25 years ago and are widely used in the clinical laboratory today for routine collection of blood. These tubes have gained widespread acceptance due to the advantage of the barrier gel that facilitates rapid separation of serum from cellular constituents of blood and thus reduces hemolysis. However, there are some limitations associated with gel tubes Ži.e., gel stability and analyte incompatibilities.. The serum separator BD SSTe tubes manufactured by BD are widely used in clinical laboratories. Recently, BD has developed a new barrier gel, which is superior to the existing gel. We studied the stability of common analytes when serum specimens were stored in the new BD SSTe II tubes by comparing the performance with the existing BD SSTe tubes. We did not observe any significant reduction in concentrations of 42 commonly ordered analytes using the new BD SSTe II tubes. Significant differences were noted at low serum volumes for estradiol in both tube types over time. We conclude that the new BD SSTe II tubes are suitable for collection of blood and storage of serum for commonly ordered laboratory tests. q 2001 Elsevier Science B.V. All rights reserved. Keywords: Barrier gel; Stability; BD SSTe II tubes

1. Introduction Plain blood collection tubes suffer from many limitations. A complete separation between serum and blood cells may not be achieved in all collections. Moreover, hemolysis of specimens upon prolonged storage is a serious problem, thus limiting the ) Corresponding author.: Tel.: q1-201-847-5739; fax: q1-201847-4857. E-mail address: Valerie – [email protected] ŽV.J. Bush..

reuse of specimen for further testing to honor AaddonB requests of tests by the ordering physicians. In order to circumvent these problems, serum separator tubes were first introduced to laboratories approximately 25 years ago by Becton Dickinson and Company ŽBD.. An inert gel moves to the serumrclot interface during centrifugation, thus providing a barrier between the serum and the clot. These tubes gained widespread acceptance largely due to the advantage of barrier gel that facilitates rapid separation of serum from cellular constituents of blood and

0009-8981r01r$ - see front matter q 2001 Elsevier Science B.V. All rights reserved. PII: S 0 0 0 9 - 8 9 8 1 Ž 0 1 . 0 0 3 9 6 - 5

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V.J. Bush et al.r Clinica Chimica Acta 306 (2001) 139–143

also prevents hemolysis on prolonged storage. Other advantages of a serum separator tube include analyte stability, primary tube sampling and storage, and reduced need for aliquot tubes. The serum separator BD SSTe tubes manufactured by BD are widely used throughout the world for blood collection. Other commercial brands of serum separator tubes are available in the US and elsewhere in the world. Analyte stability in serum separator tubes has been documented in the past w1–5x. One disadvantage of gel separator tubes is the instability of certain analytes Ži.e., therapeutic drugs and steroid hormones. when serum is stored for long periods of time on the barrier w3–8x. Another disadvantage is the instability of the gel itself under extreme temperature conditions, commonly recognized as the presence of gel globules or an oily film in the serum. These have been implicated in instrument probe clogging and subsequent down time. BD recently released a new serum separator tube containing a new gel ŽBD SSTe II. which is superior to the existing gel, with respect to analyte w9x and gel stability. The new gel is composed of a different polymeric material and provides a better barrier between serum and cellular constituents of blood as well as a wider centrifugation range. We studied the stability of commonly ordered analytes when sera were stored in the new BD SSTe II tubes compared to the current BD SSTe tubes available in the market. 2. Materials and methods Two separate studies were undertaken to evaluate the stability of chemistry analytes in the new BD SSTe II tubes with paired samples. 2.1. Part 1 The first study entailed collecting two tubes from patients. Both were collected from each patient in a randomized order after obtaining informed consent. A total of 30 healthy donor samples and 28 patient samples outside the normal reference range were recruited for the study. Patient specimens were analyzed for their regularly ordered tests so that the sample size varies among the different analytes. All patients were adults ŽG 18 years., with a mix of males and females. The 13 = 100 mm BD SSTe

Plus Žcatalog a367973. tube was the laboratory’s usual tube and served as the control. Values from the BD SSTe tube were compared to those from the 16 = 100 mm BD SSTe II Žcatalog a367958.. Visual assessment of the gel tubes was documented relative to barrier formation and appearance after centrifugation. Specimen handling was according to standard laboratory practice Žallowed to clot for 30 min, centrifuged at 1100 = g for 10 min.. Each sample was tested twice: initially Žwithin 2 h of collection., and 24 " 2 h after the initial test. Storage of samples between testing intervals was at 48C. 2.2. Part 2 Stored serum collected from patients during their regularly scheduled visit was used for the second Table 1 Instruments and analytes tested Part 1: patient blood

Part 2: patient serum

Hitachi 917

Abbott AxSYM w

Opus Magnum

CA-125 HbsAg HCV HIV 1,2 Troponin I

Testosterone Progesterone

Beckman Access w

Sodium Vitamin B12 Potassium Folate Chloride Bicarbonate Glucose Urea Creatinine Uric acid Calcium Phosphorus Magnesium Total protein Albumin Total bilirubin ALKP ALT AST LD GGT CK Triglyceride Cholesterol HDL-C LDL-C Iron Ferritin Transferrin Amylase

Abbott IMx Hitachi 717 Free T3 Myoglobin Free T4 TSH Estradiol Beckman Array w Ceruloplasmin

V.J. Bush et al.r Clinica Chimica Acta 306 (2001) 139–143

portion of the study. One milliliter of serum from different patients was added to each of the two tubes Ž16 = 100 mm BD SSTe and SSTe II., for a total of 10 patients. Serum was placed on the gel to simulate post centrifugation practice. One milliliter of serum was selected intentionally to exaggerate any absorption effects by the gels in each tube. These samples were analyzed at t s 0 and t s 24 " 2 h. The initial time testing was conducted when serum was first added to each tube Ž t s 0.. The samples were stored at 48C for 24 h according to standard laboratory practice and re-tested after the storage period. We studied 43 different analytes for parts 1 and 2 to ensure that the stability of analytes frequently

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ordered by the physicians were covered. The analytes and the automated analyzer used for measuring them are given in Table 1 Statistical comparisons of results included: descriptive statistics and analysis of variance ŽANOVA.. Absorbance units for the viral markers were recorded and assessed for misclassification. The ANOVA compared tubes over time and for overall interactions using the following model: y s donor q tube q time q tube = time q error. A level of significance was set at a s 0.05. Given that the interaction effect Žtime = tube. was significant for some analytes, to assess tube effects within a time interval, a separate ANOVA between the tubes were calculated. This second ANOVA compared pairs of

Table 2 Summary of patient blood results ŽPart 1. Analyte

Sodium Žmmolrl. Potassium Žmmolrl. Chloride Žmmolrl. Bicarbonate Žmmolrl. Glucose Žmmolrl. Urea Žmmolrl. Creatinine Žmmolrl. Uric acid Žmmolrl. Calcium Žmmolrl. Magnesium Žmmolrl. Phosphorus Žmmolrl. Total protein Žgrl. Albumin Žgrl. Total bilirubin Žmmolrl. ALKP ŽUrl. ALT ŽUrl. AST ŽUrl. GGT ŽUrl. LD ŽUrl. Total CK ŽUrl. Triglyceride Žmmolrl. Cholesterol Žmmolrl. HDL Žmmolrl. LDL Žmmolrl. Amylase ŽUrl. Iron Žmmolrl. Transferrin Žgrl. Ferritin Žngrml. Vitamin B12 Žpmolrl. Folate Žnmolrl. )

Sample size

58 58 58 58 58 58 58 58 58 45 58 58 58 58 58 58 58 58 58 58 58 58 45 45 45 45 45 45 28 28

BD SSTe Initial time

BD SSTe II

Mean " SD

Mean " SD

141 " 2.46 4.2 " 0.38 104 " 3.4 25 " 2.8 6.2 " 1.72 7.2 " 4.68 0.11 " 0.078 0.36 " 0.136 2.27 " 0.118 0.81 " 0.067 1.20 " 0.305 70 " 6.6 39 " 4.8 10 " 6.3 107 " 73.9 26 " 28.8 27 " 26.4 58 " 97.5 182 " 97.4 91 " 131.8 1.7 " 1.04 5.4 " 1.34 1.4 " 0.43 3.2 " 1.01 75 " 42.3 15.5 " 7.6 2.7 " 0.54 306 " 372.4 252 " 89.7 16 " 7.2

141 " 2.44 4.2 " 0.36 104 " 3.5 26 " 2.8 6.2 " 1.72 7.2 " 4.72 0.11 " 0.077 0.36 " 0.136 2.29 " 0.114 0.81 " 0.062 1.21 " 0.301 72 " 6.5 40 " 4.6 10 " 6.3 108 " 74.4 26 " 29.1 27 " 27.0 58 " 98.3 181 " 97.6 92 " 135.5 1.7 " 1.05 5.5 " 1.34 1.4 " 0.44 3.3 " .099 75 " 42.4 15.6 " 7.5 2.7 " 0.54 319 " 392.6 247 " 93.7 16 " 7.1

p value - 0.05 is statistically significant and indicated in bold.

p)

0.107 0.901 0.553 0.000 0.450 0.203 0.228 0.090 0.000 0.413 0.000 0.000 0.000 0.709 0.004 0.061 0.800 0.116 0.255 0.008 0.028 0.000 0.007 0.000 0.017 0.262 0.000 0.021 0.202 0.0772

BD SSTe 24 Hours

BD SSTe II

Mean " SD

Mean " SD

142 " 2.77 4.2 " 0.38 105 " 3.6 24 " 3.1 6.2 " 1.68 7.2 " 4.64 0.11 " 0.078 0.36 " 0.133 2.28 " 0.115 0.81 " 0.074 1.21 " 0.309 70 " 6.9 39 " 4.9 10 " 65.6 118 " 118.6 26 " 27.8 28 " 27.6 56 " 93.9 179 " 92.0 89 " 123.6 1.7 " 1.04 5.4 " 1.39 1.4 " 0.42 3.3 " 1.01 75 " 42.3 15.6 " 7.7 2.7 " 0.53 323 " 387.9 241 " 92.2 16 " 7.0

142 " 2.65 4.2 " 0.36 105 " 3.6 25 " 3.1 6.2 " 1.70 7.3 " 4.66 0.11 " 0.078 0.36 " 0.135 2.29 " 0.115 0.81 " 0.082 1.21 " 0.309 72 " 6.9 39 " 4.8 10 " 5.8 119 " 120.4 26 " 28.4 28 " 27.5 57 " 97.9 176 " 91.0 91 " 131.6 1.7 " 1.04 5.5 " 1.37 1.4 " 0.42 3.3 " 1.01 75 " 42.3 15.6 " 7.7 2.7 " 0.54 328 " 392.3 244 " 96.4 16 " 7.2

p)

0.077 0.502 0.510 0.000 0.024 0.006 0.209 0.001 0.000 0.254 0.169 0.000 0.000 1.000 0.098 0.002 0.502 0.203 0.001 0.091 1.000 0.621 0.003 0.000 0.043 0.445 0.000 0.932 0.103 0.136

V.J. Bush et al.r Clinica Chimica Acta 306 (2001) 139–143

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values among donors, and not means, with an adjusted a s 0.025. Thus, while the descriptive statistics in Tables 2 and 3 may not appear different, statistical differences among pairs were noted leading to a significant p value. Additionally, the data were evaluated for clinically significant differences according to limits set by the Clinical Laboratory Improvement Act ŽCLIA. w10x. Where CLIA limits do not exist for a particular analyte, we calculated clinical limits as described by Zhang et al. w11x.

3. Results The laboratory found the barrier formation and appearance between the two gel tubes to be equivalent. Slightly more red blood cells ŽRBC. were noted in the BD SSTe II gel because of its transparent appearance. This poses no analytical problems since the RBCs are embedded in the gel and do not migrate to the surface. In fact, a clear barrier may be preferred in differentiating the interface between the serum and clot. Additionally, the BD SSTe II provides a more stable barrier and wider centrifugation conditions than the BD SSTe Ždata not shown..

3.1. Part 1: patient blood The means and standard deviations ŽSD. of the control and evaluation tubes at initial time and 24 h post-collection for the first portion of the study are shown in Table 2. While some statistical differences were found, none were found to be clinically significant. In fact, stability of all analytes in Table 2 was good in both tubes. No clinical differences between time points were found in either SST or SST II among the analytes in Table 2. In comparing differences between tube types, a slight positive bias Žmaximum difference of 4 grl, average difference of 2 grl. in the BD SSTe II tube, compared to the BD SSTe tube, was shown for total protein at both time points. Some difference in LD Žmaximum of 20 Url. was noted between two tube types t s 24 h. These slight biases may be due to vigorous mixing of the sample post collection, cellular contamination of the serum andror the time to analysis. Three BD SSTe II tubes contained hemolysis compared to one BD SSTe tube Žout of a total of 58.. Both tubes were handled equivalently and cellular contamination of the serum after centrifugation was occasionally noted in both tubes. If the barrier did not form correctly or cells remained

Table 3 Summary results for patient serum ŽPart 2. Analyte

Free T3 Žngrdl. Free T4 Žmgrdl. TSH ŽmIUrdl. Estradiol Žpgrml. Testosterone Žngrdl. Progesterone Žngrml. Myoglobin Žngrml. Troponin I Žmgrml. Ceruloplasmin Žmgrdl. CA-125 ŽUrml. HbsAg a HCV a HIV 1,2 a ) a

Sample size

10 10 10 10 10 10 10 10 10 10 10 10 10

BD SSTe Initial time

BD SSTe II

Mean " SD

Mean " SD

4.70 " 3.34 1.57 " 0. 85 7.25 " 6.65 91 " 59.0 290 " 210.1 20 " 19.7 258.4 " 333.6 28.2 " 52.0 40 " 4.97 110.5 " 73.5 0.007 " 0.005 0.259 " 0.100 0.320 " 0.818

4.71 " 3.34 1.57 " 0.85 7.31 " 6.67 91 " 59.3 290 " 210.1 20 " 19.6 258.4 " 333.6 28.2 " 52.0 40 " 4.97 110.5 " 73.5 0.007 " 0.005 0.259 " 0.100 0.320 " 0.818

p)

0.869 0.823 0.941 0.167 0.221 0.728 0.048 0.737 0.183 0.236 NA NA NA

BD SSTe 24 h

BD SSTe II

Mean " SD

Mean " SD

5.1 " 3.28 1.55 " 0.84 8.45 " 9.48 68 " 46.6 273 " 194.5 19 " 16.4 261.7 " 321.86 26.2 " 47.8 42 " 4.81 112.3 " 68.6 0.008 " 0.010 0.182 " 0.055 0.011 " 0.006

5.06 " 3.07 1.61 " 0.92 8.42 " 9.35 80 " 55.9 270 " 193.5 19 " 16.9 265.5 "338.17 25.5 " 48.9 41 " 5.08 118.7 " 79.5 0.008 " 0.008 0.185 " 0.050 0.011 " 0.004

p)

0.470 0.121 0.570 0.018 0.411 0.040 0.612 0.498 0.059 0.010 NA NA NA

p value - 0.05 is statistically significant and indicated in bold. Viral markers reported in absorbance units and values assessed for mis-classification. NA denotes statistical analysis was not applied.

V.J. Bush et al.r Clinica Chimica Acta 306 (2001) 139–143

on top of the barrier, cellular contamination of the serum would result. 3.2. Part 2: patient serum Table 3 shows the results from the second portion of the study with the patient serum samples placed in the gel tubes. Significant differences between time intervals were shown for estradiol, progesterone and CA-125 in both the SST and SST II. All other analytes showed good stability over time within a tube type.

4. Discussion No significant differences were found between the tubes at initial time for all analytes tested. However, statistical differences were shown for CA-125, estradiol and progesterone at the 24-h testing interval. On average, a decrease in values was noted for estradiol and progesterone in both tubes after 24-h storage, but progesterone values were not considered clinically significant. Instability of estradiol and progesterone in SSTe tubes has been shown previously and is volume dependent w7,8x. The present study used a reduced serum volume Ž1 ml of serum. on the gel of the tubes than would normally be seen with a full draw tube Ž3–4 ml of serum. after centrifugation. While the recovery of estradiol was improved with the BD SSTe II product, clinically significant differences were found for both tubes at these low serum volumes on the barrier. Greater recoveries would be expected with larger sample volumes on the gel. The difference in CA-125 at 24 h was not considered clinically significant. No misclassifications of the viral markers were noted. We conclude that the BD SSTe II Plus tubes provide a clear stable barrier between the serum and the clot. The phlebotomy team and laboratory reported no difference between the performance of the

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tubes. The BD SSTe II Plus tubes performed equivalently to the current BD SSTe Plus tubes for analyte compatibility at initial time and after 24 h at 48C storage on the gel. Caution should be used when storing serum in gel tubes for estradiol, especially at low sample volumes on the gel. References w1x Laessig RH, Westgard JO, Carey RN, Hassemer DJ, Schwartz TH, Feldbruegge DH. Assessment of serum separator device for obtaining serum specimens suitable for clinical analyses. Clin Chem 1976;22:235–8. w2x Hill BM, Laessig RH, Koch DD, Hassemer DJ. Comparison of plastic vs. glass evacuated serum-separator ŽBD SSTe blood drawing tubes for common clincal chemistry determinations. Clin Chem 1992;38:1474–8. w3x Reinartz JJ, Ramey ML, Fowler MC, Killeen. Plastic vs. glass BD SST evacuated serum-separator blood drawing tubes for endocrinologic analytes. Clin Chem 1993;39:2535– 6. w4x Landt M, Smith CH, Hortin GL. Evaluation of evacuated blood collection tubes: effects of three types of polymeric separators on therapeutic drug-monitoring specimens. Clin Chem 1993;39:1712–7. w5x Larsson L, Ohman S. Effect of silicone-separator tubes and storage time on ionized calcium in serum. Clin Chem 1985;31:169–706. w6x Dasgupta A, Dean R, Saldana S, Kinnaman G, McLawhon RW. Absorption of therapeutic drugs by barrier gels in serum separator blood collection tubes. Am J Clin Pathol 1994;101:456–61. w7x Reinartz JJ, Ramey ML, Fowler MC, Killeen A. Plastic vs. glass SST evacuated serum separator blood drawing tubes for endocrinologic analytes. Clin Chem 1993;39:2535–6. w8x Ferry JD, Collins S, Sykes E. Effect of serum volume and time of exposure to gel barrier tubes on results for progesterone by Roche Diagnostics Elecsys 2010. Clin Chem 1999;45:1574–5. w9x Dasgupta A, Wells A, Bush V. Stability of therapeutic drugs on serum separator tubes from BD containing a new gel formulation. J Ther Drug Monit 1999;21:428. w10x CLIA, Analytical quality requirements. Fed Regist 1992;57Ž40.:7002–186. w11x Zhang DJ, Elswick RK, Miller WG, Bailey JL. Effect of serum-clot contact time on clinical chemistry laboratory results. Clin Chem 1998;44:1325–33....