Detecting Siemens macrotroponin by a point of care high sensitivity troponin I assay: A first look

• Techniques for macrotroponin detection tend to be slow and resource intensive. • A point of care hs-cTnI can be used by central laboratory as a comparative method. • Discordance between Atellica and iSTAT hs-cTnI rapidly detects many macrotroponins. Macrotroponins are increasingly recognized as the most common interference that confound interpretation of high sensitivity troponin I (hs-cTnI) results. Techniques for detection of macrotroponin presence tend to be slow and resource intensive. We evaluated the possibility of using a novel point of care hs-cTnI assay to rapidly distinguish samples with macrotroponin when original testing is performed on the Siemens Atellica hs-cTnI. 64 residual plasma specimens from 56 patients with low likelihood of macrotroponin (reference group) were retested on iSTAT hs-cTnI. A second group of 29 samples with previously confirmed macrotroponin I using selective IgG depletion were also re-tested on both assays (macrotroponin group). In the reference group samples, all except 4 showed close agreement between methods (median bias = −1.4% 90% CI −7.2%, +2.4%) whereas macrotroponin-positive samples generally showed larger biases (median bias = −57% 90% CI −68%, −52%). All 4 clearly discordant samples in the reference group showed low recovery after IgG depletion consistent with presence of macrotroponin. Despite the bias, 93% of macrotroponin-positive samples also produced iSTAT hs-TnI results above its sex-specific 99th percentiles. These preliminary data suggest analysing plasma on iSTAT hs-cTnI is a promising tool for rapid and specific macrotoponin detection in the central laboratory for investigation of clinically discordant troponin results produced by the Siemens Atellica platform.