Measurement of cardiac troponin I in serum with a new high-sensitivity assay in a large multi-ethnic Asian cohort and the impact of gender.

Background: As new high-sensitivity (hs) cardiac troponin (cTn) assays are introduced decision limits, based on the 99th percentile upper reference limit (99 percentile URL), for each method must be determined and from a sufficiently large cohort to mitigate against distortionary effects of high-end outliers. There is a paucity of studies with large multi-ethnic cohorts.

Methods: We determined the 99 percentile URL in 1120 (mean age: 50.4±8.2 y) apparently healthy (no history of diabetes, hypertension, heart, lung, or renal disease) Asians (597 men aged 35-65 y, 523 women aged 40-65 y) in a pre-market hs-cTnI assay (Abbott Diagnostics).

Results: Hs-cTnI performance was: limit of blank - 0.6 ng/l, limit of detection (LoD) - 1.5 ng/l; cTnI inter-assay coefficient of variation of 20% and 10% were 1.5 and 6.0 ng/l respectively. Hs-cTnI concentrations (range: 0-49.3 ng/l) were detectable (>assay LoD) in 92.3% of participants, and higher in men and individuals >50 y. All-subject, male, and female 99 percentile URL (90% CI) were 25.6 (19.6-32.6), 32.7 (21.1-47.9) and 17.9 (10.7-26.3) ng/l respectively.

Conclusion: This hs-cTnI assay exhibits hs performance besides gender and age differences. The all-subject 99 percentile URL values are similar to those reported from some groups but not in others. Users need to establish their own decision limits.