Agreement between troponin T levels from plain and heparinized tubes

To determine whether there was a clinically significant effect on troponin T measurement when the sample was collected in a heparinized (plasma) blood collection tube compared with a serum tube.

Prospective cohort study using a convenience sample of 198 patients with undifferentiated illness presenting to an Emergency Department who required troponin T measurement. Samples were collected in both plain (serum) tubes and plasma tubes for comparison. All samples were measured using an Elecsys 2010 Immunoassay system (Roche-Boehringer Mannheim, Germany).

There were 35 troponin T measurements > or = 0.03 microg/L (the limit of reproducibility of the test). The negative predictive value for troponin T performed in heparinized tubes compared with plain tubes was 100% (95% confidence interval 96.4-100) at the > or = 0.03 microg/L level and 100% (95% confidence interval 97-100%) at the > or = 0.1 microg/L level. At a cut-off point for risk stratification in acute coronary syndromes (> or = 0.1 microg/L), there was 100% concordance between the two measurements for each sample.

The use of plasma (heparinized) tubes for the collection of troponin T samples is unlikely to produce clinically significant false-negative results compared with collection of troponin T samples in serum (plain) tubes.