One-year in vitro stability of cardiac troponins and galectin-3 in different sample types.

Background: We assessed the long-term in vitro stability of cardiac troponins and galectin-3 under different storage conditions.

Methods: We used high-sensitivity cardiac troponin I (hs-cTnI) and galectin-3 assays from Abbott and a high-sensitivity cardiac troponin T (hs-cTnT) assay from Roche. The analyte concentrations of 30 patients were measured in heparin-treated plasma, EDTA-treated plasma and serum samples after the following storage conditions: 1) samples used immediately after blood collection for baseline measurements; 2) samples stored for 0.5year at -80°C after one freeze-thaw cycle; 3) samples stored for 1.0year at -80°C after two freeze-thaw cycles; and 4) samples stored for 1.0year at -80°C after one freeze-thaw cycle. According to the concept of acceptable change limits (ACL) the analytes were considered stable as long as the median concentration at a particular time point was >80%.

Results: Baseline hs-cTnI, hs-cTnT and galectin-3 concentrations ranged from 2.3 to 5436ng/L, from 5.3 to 850ng/L, and from 8.3 to 79.3ng/mL, respectively. After applying the default criterion for analyte stability, the three analytes were stable for at least 1.0year even after two freeze-thaw cycles for each sample type. We observed the following variation in analyte concentrations after storage relative to the baseline values: the interquartile range (IQR) of cardiac troponin results extended from approx. 80 to 115%, and the IQR of galectin-3 results extended from approx. 90 to 110%.

Conclusion: hs-cTnI, hs-cTnT and galectin-3 were stable under the reported storage conditions irrespective of the sample type used. However, we observed a considerable variation in analyte concentrations after sample storage, which might affect the diagnostic/prognostic value of these analytes in individual patients using frozen blood samples.