Valerie Bush

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

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 (i.e., gel stability and analyte incompatibilities). The serum separator BD SST 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 SST II tubes by comparing the performance with the existing BD SST tubes. We did not observe any significant reduction in concentrations of 42 commonly ordered analytes using the new BD SST II tubes. Significant differences were noted at low serum volumes for estradiol in both tube types over time. We conclude that the new BD SST II tubes are suitable for collection of blood and storage of serum for commonly ordered laboratory tests.

The Evolution of Evacuated Blood Collection Tubes

“A laboratory test is no better than the specimen, and the specimen no better than the manner in which it was collected.” So stated the advertising language of BD (Becton Dickinson and Company) to promote the first evacuated blood collection tubes, back in the late 1940s and early 1950s.1 This technology for blood collection, patented in 1949, is substantially similar to the technology pervasive in clinical practice today.

Stability of therapeutic drugs in serum collected in vacutainer serum separator tubes containing a new gel (SST II).

The stability of therapeutic drugs in sera collected in Becton-Dickinson Vacutainer serum separator SST tubes has been well studied. Although most therapeutic drugs are stable, certain drugs such as phenytoin, carbamazepine, and phenobarbital decrease in concentrations over a long storage time. To circumvent this problem, Becton-Dickinson devised a new gel formulation. The authors studied the stability of 14 commonly monitored drugs in sera when stored on the new gel of the SST II tubes and compared the concentrations of drugs in sera stored in plain tubes (no gel), those stored in the old SST tubes, and those stored in the SST II tubes containing a new serum separator gel. The concentrations of most drugs studied did not decline even after 24 hours of storage in SST II tubes. After storage for 7 days in SST II tubes, the concentration of carbamazepine declined by 10% and that of phenytoin decreased by 4%. This is a significant improvement over the existing tube, where concentrations of several drugs declined with prolonged storage. The authors conclude that new SST II tubes are effective in collecting blood for therapeutic drug monitoring.

Evaluation of Refrigerated Stability of 15 Analytes in Lithium Heparin Gel Primary Tubes

Objective: To determine the stability of 15 analytes when plasma specimens are placed in refrigerated storage to enable add-on testing. Methods: Blood samples were obtained from 40 volunteer outpatients and collected in plasma separator tubes. The tubes were spun to obtain platelet-poor plasma, which was analyzed for a comprehensive metabolic panel at 1 hour after collection and placed into refrigerated storage for subsequent analyses. Repeat analyses occurred at 8, 16, 24, 48, and 72 hours after collection. Subsets of 5 patient samples were aliquoted into secondary tubes after initial analysis and reanalyzed at the same time points. Stability was defined as no change within calculated acceptable allowable limits. Results: After refrigerated storage in the primary tube, most analytes were stable for the first 24 hours. The analytes that showed clinically significant changes after storage in the primary tube were glucose, potassium, CO 2 , and aspartate transaminase (AST). All analytes from the aliquot tubes remained stable for the duration of the study. Conclusions: The duration of stability for most analytes we tested was at least 24 hours in the gel tube or the aliquot. Analytes are stable for longer periods of time when stored in aliquot tubes, remixed, and re-spun before analysis.

Effects of Pre-analytical Variables in Therapeutic Drug Monitoring

There are many factors that can influence the quality of specimens and the accuracy of results. This chapter will discuss sources of errors in therapeutic drug monitoring during the pre-analytical phase. Topics include: in vivo patient variables; the effects of blood collection techniques and materials; specimen processing and transport; and specimen type. Laboratorians should be aware of the specimen type recommended and validated by instrument manufacturers for each drug assay on a particular platform to ensure accurate reporting of drug levels. Understanding the effects of pre-analytical factors on test results should allow the laboratory to better manage the pre-analytical phase for improved specimen quality.