Stability of Cardiac Biomarkers Tested in Different Samples

Blood-based biomarkers, such as cardiac troponin (cTn) and galectin-3, are widely used in clinical trials and/or in clinical routines as an aid for the diagnosis and risk stratification of patients with heart disease.

When blood samples are used for biomarker measurements in clinical routine analyses, efforts should be made to process these samples immediately after blood collection to provide immediate results for timely diagnosis and therapy and to avoid any pre-analytical errors.

Doctors at Konventhospital Barmherzige Brueder Linz, (Linz, Austria) tested the hypothesis that the analytes hs-cTnI, hs-cTnT and galectin-3 are stable in vitro at a storage temperature of −80 °C for at least one year, and they used blood samples from clinical routine analyses. 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 six months at −80 °C after one freeze-thaw cycle; 3) samples stored for one year at −80 °C after two freeze-thaw cycles; and 4) samples stored for one year at −80 °C after one freeze-thaw cycle.

Circulating concentrations of high-sensitivity cardiac troponin I (hs-cTnI) were measured with the STAT High Sensitive Troponin-I assay on the Abbott ARCHITECT i2000SR analyzer. The team measured hs-cTnT concentrations with the Troponin T hs assay on the Roche cobas e 411. The scientists also measured galectin-3 with the Abbott Diagnostics routine Galectin-3 assay on an ARCHITECT i2000SR analyzer.

The investigators reported that baseline hs-cTnI, hs-cTnT and galectin-3 concentrations ranged from 2.3 to 5,436 ng/L, from 5.3 to 850 ng/L, and from 8.3 to 79.3 ng/mL, respectively. After applying the default criterion for analyte stability, the three analytes were stable for at least one year even after two freeze-thaw cycles for each sample type. They 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%.

The authors concluded that hs-cTnI, hs-cTnT and galectin-3 were stable under the reported storage conditions irrespective of the sample type used. However, they 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. The study was published in the January 2018 issue of the journal Clinica Chimica Acta.

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