Establishing the 99th percentile of a novel assay for high-sensitivity troponin I in a healthy blood donor population.Background
 The recommended cut-off of cardiac troponin (cTn) for the diagnosis of acute myocardial infarction (AMI) is the 99th percentile in a healthy reference population.  We aimed to determine the 99th percentile of the novel ADVIA Centaur® High Sensitivity Troponin I assay (Siemens Healthcare Diagnostics) in fresh lithium heparin plasma samples from healthy blood donors.


 A total of 1000 apparently healthy blood donors were included.  High-sensitivity (hs) cTnI, hs-cTnT, creatinine and N-terminal pro b-type natriuretic peptide (NT-proBNP) were measured in fresh lithium heparin plasma samples, and glycated hemoglobin (HbA1c) was measured in ethylenediaminetetraacetic acid (EDTA)-blood.  The 99th percentile was estimated for the whole population, as well as for males and females separately.


 For the total population the 99th percentile of ADVIA Centaur® High Sensitivity Troponin I was 96 (65-149) ng/L.  The estimated value differed significantly from results published by others and was highly dependent on which values were considered statistical outliers.


 Conclusions
 The estimated 99th percentile for hs-cTnI in the population studied differed significantly from previously published results.  There is a need for further specifications regarding how subjects used for estimating the 99th percentile of cTns in healthy populations should be recruited and how outlier values should be identified, as this can highly influence the diagnostic cut-off applied for AMI.
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