Short-term increases of plasma cardiac troponin I are better evaluated by comparison with the reference change value

We have investigated consecutive troponin I measurements using the Reference Change Value (RCV) at low concentrations, in patients admitted in Emergency Department (ED). Materials and methods: Patients admitted for chest pain (N = 103) were evaluated retrospectively on the basis of two consecutive cardiac troponin-I (cTn-I) tests. The second test levels exceeding the "Critical Reference Change Value" (CrRCV), a quantity calculated on the basis of the fi rst result and the RCV of cTn-I, were considered particularly relevant. Clinical cases were analysed matching the concentration change (signifi cative or not) with acute coronary syndrome (clinically confi rmed or not). Healthy individuals (N = 70) results and internal quality control results were evaluated for the calculation of, respectively, the biological and the analytical variation of plasma cTn-I. Results: The cTn-I RCV was very high because of the high analytical variation of cTn-I in proximity of its decision limit, as shown by its imprecision profi le study. Analysing data with the fi rst result < 0.1 g/L we have obtained an cTn-I RCV negative predictive value -NPV = 88% (95% CI = 82-92%). The 4 groups of patients have demonstrated a clinically signifi cant diff erence (Chi square test; P < 0.001).