Biological variation and reference change value of high-sensitivity troponin T in healthy individuals during short and intermediate follow-up periods.

BACKGROUND Acute myocardial infarction is defined by a troponin concentration >99th percentile with an acute increase and/or decrease, the magnitude of which has not yet been well defined. To aid the interpretation of changes in cardiac troponin concentration, we sought to establish biological variation and reference change values (RCVs) by applying both the normal and lognormal approaches for cardiac troponin T (cTnT) sampled at hourly and weekly intervals in healthy individuals and measured on the Roche E 170 and Elecsys® 2010 automated platforms. METHODS High-sensitivity cTnT (hsTnT) was measured at baseline, and after 1, 2, 3, and 4 h and after 1, 2, 3, and 4 weeks in 20 and 17 healthy individuals, respectively. A healthy status was established by physical examination, MRI analysis at rest and during dobutamine stress, lung function testing, and blood sample testing. RESULTS Hourly total and within-individual CVs were 18% and 15%, respectively, for the E 170 assay, and 24% and 21%, respectively, for the Elecsys 2010 assay. Weekly total and within-individual CVs for these assays were 32% and 31%, respectively, for the E 170 assay, and 32% and 30%, respectively, for the Elecsys 2010 assay. The RCVs for the E 170 and Elecsys 2010 assays were ±46% and ±62% (hourly), respectively, and ±87% and ±86% (weekly), respectively. The corresponding lognormal values were +64%/-39% and +90%/-47% (hourly), and +138%/-58% and +135%/-58% (weekly). CONCLUSIONS RCVs appear attractive for interpreting hsTnT results. The short-term biological variation of hsTnT is low but becomes somewhat more important at intermediate sampling intervals. Knowledge of this variation is important for interpreting results from patients in whom cTnT values increase from low concentrations.