Serum Tubes Reduce False Positive Troponin Results

Blood samples collected in both Rapid Serum Tubes (RST) and Plasma Separator Tubes (PST) have been compared for cardiac troponin analysis.

Plasma samples are often used for cardiac troponin testing because they allow for faster turnaround time compared to serum separator tubes (SST), which require up to 30 minutes to clot.

Scientists at the Mayo Clinic (Rochester MN, USA) measured cardiac troponin (cTnT) concentrations in 443 emergency department patients who had a cardiac biomarker panel ordered and had both RST and PST specimens collected. All cTnT analysis was performed using the 4th generation Roche Troponin T STAT assay on a single Roche Cobas e411 analyzer (Roche Diagnostics, Indianapolis, IN, USA).

The serum RST and plasma PST collection tubes used are products of Becton–Dickinson and Company (Franklin Lakes, NJ, USA). The investigators determined the mean bias between the RST and PST cTnT concentrations, as well as the clinical concordance between RST and PST results. Clinically concordant results were defined as cTnT results either both being undetectable at less than 0.01 ng/mL, or if detectable, equal or greater than 0.01 ng/mL, a difference of equal or greater than 0.02 ng/mL between specimen types.

In 328 of 443 samples, cTnT concentrations were undetectable in both the RST and PST tubes. Seven samples had a detectable cTnT result from the PST tube, but had undetectable cTnT in the RST tube collected simultaneously. Rare false positive results in lithium heparin samples were not observed with rapid clot serum tubes. Clinically discordant cTnT results were observed between PST and RST in 10 of the 443 patient samples, with three of these being very elevated cTnT results to the degree that the diagnosis would have not been affected if cTnT results were used from either PST or RST samples.

The authors concluded that that samples collected in RST tubes yield cTnT results, which are analytically and clinically concordant to samples collected in PST tubes. Similar to studies of Troponin I on the Beckman-Coulter (Brea, CA, USA) platform they found that use of RST for collection of cardiac biomarker specimens may reduce the incidence of false positive Roche Troponin T results. The study was published in the July 2012 issue of the journal Clinical Biochemistry.

Related Links:
Roche Diagnostics
Becton–Dickinson and Company
Beckman–Coulter