The imprecision for a high-sensitivity cardiac troponin assay and a CA 19-9 assay in samples with high C-reactive protein concentrations.

We have recently detailed that the Ortho Clinical Diagnostics (OCD) hsTnI assay can yield non-reproducible elevated concentrations in patients with an acute phase response [1-6]. Early in these investigations, an initial repeat testing of 10 patient samples (EDTA plasma) from the emergency department (ED) at the Juravinski Hospital and Cancer Centre identified one poor repeat measurement (coefficient of variation (CV)>20%) at a concentration above the upper limit of normal (ULN) which prompted further investigation.