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Comparison of Becton Dickinson Vacutainer rapid serum tube with the serum separator tube for routine chemistry and immunoassay tests
  1. Ronald Yan1,2,
  2. Amy Lou3,4,
  3. Gail Watts1,
  4. Heather Tarr1,
  5. Hilary Smith1,
  6. Lois Kinney1,
  7. Yu Chen1,4
  1. 1Department of Laboratory Medicine, Dr. Everett Chalmers Regional Hospital, Horizon Health Network, Fredericton, New Brunswick, Canada
  2. 2Dalhousie Medical Program in New Brunswick, Saint John, New Brunswick, Canada
  3. 3Department of Pathology and Laboratory Medicine, Capital Health, Halifax, Nova Scotia, Canada
  4. 4Department of Pathology, Dalhousie University, Halifax, Nova Scotia, Canada
  1. Correspondence to Dr Yu Chen, Division of Clinical Biochemistry, Department of Laboratory Medicine, Dr Everett Chalmers Regional Hospital, Horizon Health Network, Fredericton, New Brunswick, Canada E3B 5N5; yu.chen{at}horizonNB.ca

Abstract

Aims To shorten the clotting time and resolve the delayed clotting or no clotting on specimens from patients on anticoagulant therapy, Becton Dickinson (BD) recently developed the Vacutainer rapid serum tube (RST). The aim of this study was to systematically compare the new RST tube with the widely used serum separator tube (SST) for routine chemistry and immunoassay tests on 3 common analyser platforms.

Methods Blood from 45 people (24 women and 21 men, age 21–77 years) was collected using the SST and RST tubes in sequence. Sera from both tubes were separated and analysed simultaneously for 54, 50, and 10 chemistry and/or immunoassay tests on the Roche Modular, Abbott Architect, and Siemens Centaur analysers, respectively.

Results The results from the RST tube were comparable with those from the SST tube on most analytes. Although the results for a few analytes showed statistically significant differences between the two tubes (p<0.05), the differences had no clinical significance for most assays. Only for parathyroid hormone on the Abbott Architect, the RST tube demonstrated clinical significant bias versus the SST tube (−15.3%, p<0.01).

Conclusions The RST tube provides acceptable performance for routine chemistry and immunoassay tests.

  • CHEMICAL PATHOLOGY
  • CHEMISTRY
  • LABORATORY TESTS
  • QUALITY ASSURANCE

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Introduction

Completely clotted ‘cell free’ serum is the standard specimen for clinical chemistry and immunoassay testing.1 The Clinical and Laboratory Standards Institute (formerly the National Committee for Clinical Laboratories Standards) recommends processing of the blood collection tube within 2 h of collections to minimise preanalytical errors in the serum from contact with cells.1 Serum tubes with gel separator are widely used in clinical laboratories, especially for those with a preanalytical automation. As with all other serum tubes, the Becton Dickinson serum separator tube (SST) requires a blood clotting time of at least 30 min. This practice does not meet the demand for faster laboratory result turn-around time (TAT) in critical care units, such as emergency departments and intensive care units to reduce the time to make decisions, interventions, and shorten patient's length of stay. Even for clinical programmes based outside the hospital (eg, New Brunswick's Extramural Program) and remote blood collection sites, this clotting time may be excessive for a timely separation of samples in order to facilitate transport to the regional laboratory. Plasma has been proposed as an alternate specimen type for clinical chemistry testing,2 however, plasma has its well-known limitations, such as higher cell counts, reduced storage stability for certain analytes, potential interference from fibrinogen and anticoagulants among others. To provide laboratories with a fast turn-around time similar to a plasma specimen, and the quality of a properly clotted serum specimen, BD recently developed a Vacutainer rapid serum tube (RST) containing bovine thrombin and gel technology to speed blood clotting time to 3–5 min.3 The RST tube may also resolve the slow clotting or no clotting problem with the specimens from dialysis patients or patients undergoing thrombolytic therapy. If validated, the RST tube may also ease the stress that medical laboratory technologists face from the prolonged clotting time, demand for a faster TAT, and the risk of the latent clotting which may cause analyser probe clog and/or erroneous test results.

Although BD has carried out a few studies, most of which were on selected chemistry analytes, independent third party validation data for the performance of the new RST tube remains scarce. Recently, Dimeski et al have demonstrated satisfactory performance of the RST tube compared with the lithium heparin plasma separator tube (PST) for 31 analytes on Beckman DxC800 and DxI800 analysers.4 Although high-sensitivity troponin T and creatine kinase-MB did not significantly differ between the RST and SST tubes,5 the RST tube has been suggested to reduce false positive results of troponin I by the PST, PST II and SST II tubes on the DxI800 analyser,4 ,6 and of troponin T by the PST tube on the Roche Cobas e411 analyser.7 Comparable results were also reported for the RST tube against the SST II tubes on serum potassium and lactate dehydrogenase.8

The aim of this study was to systematically compare the new RST tube with the well established SST tube for thorough routine chemistry and immunoassay panels on three other common analyser platforms—the Roche Modular, Abbott Architect and Siemens Centaur analysers.

Materials and methods

Specimens and blood collection

Blood samples were collected from 28 healthy volunteers and 17 patients to help span the analytical range for routine chemistry and immunoassay tests. Among them, there were 24 women and 21 men with an age range of 21–77 years. The study was performed at the Dr Everett Chalmers Regional Hospital, Horizon Health Network, Fredericton, New Brunswick, Canada, with appropriate ethics approval, and with informed consent from the participants. Blood was collected using the SST (BD REF #367986) and RST (BD REF #368774) tubes in sequence. Sera were separated according to the BDs and analyser/reagent manufacturer’s instructions, aliquoted and stored at −20°C until analysis.

Routine chemistry and immunoassay measurements

Sera from the RST and the SST tubes were analysed simultaneously for a panel of routine chemistry assays and immunoassays on a Roche Modular analyser (54 analytes) and Siemens Centaur (10 hormone analytes) at the Dr Everett Chalmers Regional Hospital. A set of serum aliquots were analysed simultaneously for 50 analytes on the Abbott Architect ci8200 at the Queen Elizabeth Hospital laboratory, in Charlottetown, Prince Edward Island, Canada (under the supervision of coauthor AL). All analyses of the particular same analyte were conducted in one quality controlled analytical run. N<45 for some assays was due to the sex-specific nature of the anylates (eg, prostate-specific antigen, β-human chorionic gonadotropin, etc) and/or values below the lower limit of quantitation (eg, troponin). RST tube did not demonstrate significant difference compared with the SST tube on specimen integrity as to the haemolysis, icterus and lipaemia serum indices.

Statistical analysis

Statistical analysis was carried out using the SPSS V.20.0 software (IBM Corporation, Armonk, New York, USA). Sample data was tested for normality using the Shapiro–Wilk test. Data drawn from a normal population (Shapiro–Wilk p>0.05) were expressed as mean±SD, and were compared using a paired Student t test. Sample data for analytes found to be from non-normally distributed populations were expressed as median with IQR, and were compared using a Wilcoxon signed rank test performed with the ‘exact’ method. P<0.05 was considered as statistically significant. Generally, clinical significance was judged by bias >10% compared with values from the SST tube, or more stringently by other common clinical acceptance limits (CAL, eg, 0.075 mmol/L for calcium, 0.3 mmol/L for potassium, 3 mmol/L for sodium, 5% for total protein and high density lipoprotein cholesterol, etc).9

Results

Comparison of the RST tube with the SST tube on Roche Modular assays

The results from the RST tube were comparable with those from the SST tube on all 54 analytes on the Roche modular platform (tables 1 and 2). Although there was statistical significance in 11 analytes, the difference between the RST and the SST tubes were all less than 10% and the CALs.

Table 1

Comparison of Becton Dickinson Vacutainer rapid serum tube (RST) with the serum separator tube (SST) on Roche Modular platform assays—analytes with normal distribution

Table 2

Comparison of Becton Dickinson Vacutainer rapid serum tube (RST) with the serum separator tube (SST) on Roche Modular platform assays—analytes with non-normal distribution

Comparison of the RST tube with the SST tube on Abbott Architect assays

The results from the RST tube were comparable with those from the SST tube on most analytes on the Abbott architect platform (tables 3 and 4). Although there was statistical significance in 18 analytes, the difference between the RST and the SST tubes were all less than 10% and CAL, except for parathyroid hormone (PTH), in which the RST tube demonstrated clinically significant bias versus the SST tube (−15.3%, p<0.01). Due to nature of healthy subjects’ participation in the study, many results were below the lower limit of quantitation, therefore, the statistical analysis of RST tube versus the SST tube on troponin I, BNP and βHCG were not performed, but their testing values were comparable based on small sample sizes.

Table 3

Comparison of Becton Dickinson Vacutainer rapid serum tube (RST) with the serum separator tube (SST) on Abbott Architect platform assays—analytes with normal distribution

Table 4

Comparison of Becton Dickinson Vacutainer rapid serum tube (RST) with the serum separator tube (SST) on Abbott Architect platform assays—analytes with non-normal distribution

Comparison of the RST tube with the SST tube on Siemens Centaur assays

The results from the RST tube were comparable with those from the SST tube on all 10 hormone analytes on the Siemens Centaur platform (table 5). Although there was statistical significance in oestradiol, the difference between the RST and the SST tubes was 8% (p=0.022). There was a –9.6% bias for progesterone, however, this was not statistically significant (p=0.178).

Table 5

Comparison of Becton Dickinson Vacutainer rapid serum tube (RST) with the serum separator tube (SST) on Siemens Centaur platform immunoassays

Discussion

Generally, the RST tubes performed similarly to the more established SST tube on routine chemistry and immunoassay tests on Roche Modular, Abbott Architect and Siemens Centaur platforms. The RST tubes demonstrated statistically significant bias compared to the SST tube on a few analytes, however, the differences in all except PTH were small enough (<10% and < clinical acceptance limits (ACL)) to be deemed as clinically insignificant.

To our knowledge, this study is the first independent third party validation of the new RST tube on extensive testing panels of Roche Modular, Abbott Architect and Siemens Centaur systems. The acceptable RST tube performance makes it a promising replacement for the SST tube in clinical chemistry and immunoassay testing with significant savings on TAT of 15–20 min depending on how fast samples can be delivered. There is no doubt that this faster clotting and, consequently, shorter laboratory result TAT will ease the work of the laboratory and its clients and enhance the satisfaction of laboratorians and clinicians, eventually improving the patient care. The possibility of clinical chemistry, immunoassay and therapeutic drug monitoring testing by one blood tube draw will further benefit patients from potential risk of iatrogenic anaemia by repetitive diagnostic phlebotomy,10 ,11 streamline the laboratory workflow, and help to make it more justifiable for implementing the RST tube since its current price (∼US$0.20/tube) is the double that of the SST tube (∼US$0.10/tube).

The RST tube showed clinical significant bias compared to the SST tube (−15.3%, p<0.01) on PTH. PTH is a peptide hormone with a reported half-life of 3–5 min.12 Although serum specimen is acceptable for PTH measurement, EDTA-plasma is the preferred sample type. Serum PTH has been found to progressively decline over 72 h, while plasma PTH in the EDTA tube or protease inhibitor tube appeared stable.13 When serum is used for PTH measurement, the blood should be centrifuged immediately after clotting. Our data indicates that a more detailed stability study on PTH is needed for the new RST tube.

One drawback of the present study was that although we recruited some patients in addition to healthy volunteers to span the analytical range, for some analytes, such as troponin I, BNP and βHCG, the values of this subject population were all normal or even below the lower limit of quantitation. The RST tube performed consistently with the SST tube on these analytes. However, statistical analysis could not be done on the Abbott Architect system. The acceptability of the RST tube on troponin I and troponin T have been validated in dynamic range on Beckman DxI800 and Roche Coabas e411 analysers; furthermore, the RST tube has been shown to reduce false positive troponin results compared to the SST and PST tubes.4–7 For BNP, βHCG, oestradiol, progesterone, and so on, future validation studies with specific patient populations to cover the high end of analytical range are warranted.

From the data of this study, it can be concluded that the RST tube performs similarly to the SST tube for routine chemistry and immunoassays when analysed on Roche Modular, Abbott Architect and Siemens Centaur automated platforms. From technical and clinical perspectives, samples collected into the RST tubes are superior to the SST tubes for the reduced TAT, however, due to the higher cost of RST tubes, economic evaluation based on clinical goals and operating budgets will be helpful. There are no technical limitations precluding the use of RST tubes for routine chemistry and immunoassays, however, implementation will depend on the individual needs of a particular laboratory and its clients.

Take home messages

  • We evaluated the Becton Dickinson rapid serum tube (RST) along with the more established serum separator tube (SST) tube on routine chemistry and immunoassay tests on three common analyser platforms.

  • The results from the RST tube were comparable with those from the SST tube on most analytes.

  • Only for parathyroid hormone on the Abbott Architect, the RST tube demonstrated clinically significant bias versus the SST tube (−15.3%, p<0.01).

  • The RST tube provides acceptable performance for routine chemistry and immunoassay tests.

Acknowledgments

RY was supported by a summer studentship from the New Brunswick Health Research Foundation. The Rapid Serum Tubes were supplied by Becton Dickinson. The authors would like to thank Roche, Abbott, and Siemens for supporting immunoassay and chemistry reagents for this study.

References

Footnotes

  • Contributors RY did data analysis and drafted the manuscript. AL helped in testing, reviewed and approved the manuscript. GW, HT, HS, LK did testing, reviewed and approved the manuscript. YC designed the study, did data analysis, revised and finalised the manuscript.

  • Competing interests None.

  • Patient consent Obtained.

  • Ethics approval Horizon Health Network Ethics Board.

  • Provenance and peer review Not commissioned; externally peer reviewed.