Technical Note: Implementation of Point of Care High Sensitivity Troponin I on the i-STAT Device and Comparative...

High sensitivity troponin I (hs-TnI) is a sensitive biomarker for the diagnosis of myocardial infarction. Recently, the FDA has approved a point of care (POC) hs-TnI assay on the i-STAT device (Abbott Laboratories, Abbott Park, IL). We evaluated concordance of this assay with a laboratory based hs-TnI assay using the DXI 800 analyzer (Beckman, Brea, CA).

i-STAT device precision for hs-TnI was studied using two controls provided by the manufacturer across all i-STAT analyzers (n=68) to be used at our health system. For initial concordance study, 40 plasma specimens were analyzed using the DXI 800 hs-TnI assay and i-STAT hs-TnI assay. Then, for further evaluation, in 20 plasma specimens (10 males and 10 females), hs-TnI concentrations were determined by using two DXI analyzers (each measurement in duplicate) and 17 i-STAT devices (each run in duplicate). For overall reproducibility of results using i-STAT devices, all 68 analyzers were assessed side-by-side using a large plasma pool. Moreover, in four patients, i-STAT hs-TnI whole blood values were compared with plasma hs-TnI values using the DXI 800.

Both short- and long-term precision of hs-TnI controls demonstrated acceptability. When the mean hs-TnI concentrations obtained by the DXI 800 were plotted in the x-axis (reference method) and corresponding mean values obtained by i-STAT were plotted in the y-axis, we observed the following regression equation: y=1.06x+2.72, r=0.97, (r=0.98). When all 68 i-STAT analyzers were compared with each other using pooled plasma specimens, we observed acceptable results. Additionally, in 20 plasma specimens, where hs-TnI obtained by two DXI 800 analyzers (mean value) were plotted in the x-axis and the corresponding overall mean of hs-TnI results obtained using 17 i-Stat analyzers were plotted in the y-axis, we observed the following regression equation: y=0.97x+2.36 (r=0.98). We also observed concordance between whole blood hs-TnI and plasma-based TnI in four patients.

We observed good concordance in hs-TnI values obtained by i-STAT and DXI 800; however, due to different analytical cut-offs, assay design, and lack of a TnI standard, this concordance should not be interpreted as equivalent performance.