Determination of sex-specific 99th percentile upper reference limits for a point of care high sensitivity cardiac troponin I assay

Objectives: High sensitivity (hs) cardiac troponin (cTn) assays are defined per the IFCC Committee on Clinical Application of Cardiac Biomarker (C-CB) by the ability to measure ≥ 50% of concentrations greater than the limit of detection (LoD) with an impression of ≤10% at sex-specific 99th percentiles. Our study determined the sex-specific 99th percentile upper reference limits for males and females utilizing heparinized plasma from AACC universal sample bank for the Siemens point of care (POC) Atellica^® VTLi hs-cTnI immunoassay.

Methods: Apparently healthy subjects, included overall 693, males 363, and females 330, following exclusionary surrogate biomarker use of hemoglobin A_1c, NT-proBNP, and eGFR, along with statin medication. hs-cTnI was measured in a central laboratory, on multiple POC Atellica^® VTLi immunoassay analyzers. The LoD was 1.24 ng/L and the 10%CV concentration was 6.7 ng/L. 99th percentile URLs were determined by the nonparametric (NP) method.

Results: Histograms of the hs-cTnI concentrations (ng/L) for males and females were used to visualize the distributions and concentrations in men and women and differed significantly (pre- and post-exclusion, both p <0.001). 99th percentile URLs were: overall 23 ng/L (90% CI 20-32 ng/L); male 27 ng/L (CI 21-37 ng/L); female 18 ng/L (CI 9-78 ng/L). The percentages of subjects having a measurable concentration ≥ the LoD were: overall 83.7%, male 87.3%, female 79.7%.

Conclusions: Our findings show the novel POC Atellica^® VTLi hs-cTnI assay meets the designation of a 'high-sensitivity' assay using heparinized plasma.