Assay performance improved, but which "scorecard" designation for Vitros Troponin I?

BACKGROUND: Since cardiac troponins assay technology should comply with the recommendations of scientific societies (i.e. imprecision (10%) at the 99th percentile value observed in healthy subjects being the analytical qualifying aspect), the aim of the present study was to evaluate whether an improved troponin assay (Vitros Troponin I ES) provides data that meet the "guideline acceptable"criteria recently defined in a proposed scorecard. METHODS: Vitros Troponin I ES, an enhanced chemiluminescence immunoassay, was evaluated in a multicenter study considering: limit of blank (LOB, 60 replicates of 0 calibrators), limit of detection (LOD, 12 measurements for each of 5 serum pools), precision, linearity using control materials and serum plasma pool; matrix samples study matching serum and lithium-heparin plasma (n=107 hospitalized patients); the 99th percentile limit in serum samples from 500 healthy Caucasian donors. RESULTS: LOB and LOD, 0.0029 μg/L and 0.0030 μg/L respectively; coefficients of variation (total CV%), obtained by running 3 levels of control materials and 10 serum pools, from 15.2% (x(-)=0.014 μg/L) to 2.0% (x(-)=5.324 μg/L); method, linear up to 70 μg/L. No significant differences were found between serum and lithium-heparin matched sample (p=0.48) values; 99th percentile limit of cTnI distribution in healthy donors, 0.021 μg/L. CONCLUSION: Since its analytical reliability meets the proposed performance and scorecard requirements, the Vitros TropI method can be considered "contemporary" and "guideline acceptable".