Abstract
High-sensitivity cardiac troponin (hs-cTn) testing has enabled physicians to make earlier diagnostic and prognostic decisions in the hospital setting than previous cardiac troponin assays. Analytical improvements have permitted one to measure cardiac troponin precisely in the nanogram per litre (ng/L) range with hs-cTn assays which has resulted in fast 0/1-h and 0/2-h algorithms for ruling-in and ruling-out myocardial infarction. Although analytical interferences that affect the reporting of hs-cTn are uncommon, not all hs-cTn assays are designed the same nor have undergone the same clinical and analytical validations. Here, after investigating an initial case of discrepant hs-cTnI results, we report that patients with an acute phase response (e.g., patients with inflammatory or infectious illnesses) can yield high and non-reproducible results with the Ortho Clinical Diagnostics hs-cTnI assay. Compared to Abbott Diagnostics hs-cTnI, Ortho Clinical Diagnostics hs-cTnI assay misclassifies biochemical injury in approximately 10% of the population being assessed for myocardial injury with imprecise results in approximately half of this population (i.e., 5%). In conclusion, caution is warranted in interpreting Ortho Clinical Diagnostics hs-cTnI alone in patients being evaluated for myocardial injury, especially in patients whose primary presentation is related to an acute phase response and not an acute coronary syndrome symptom.
Highlights
Contemporary clinical and laboratory guidelines all recommend high-sensitivity cardiac troponin testing for the biochemical detection of myocardial injury [1,2,3].In patients presenting with symptoms suggestive of acute coronary syndrome (ACS) to the emergency department (ED), early measurements with either hs-cTnI or hs-cTnT may be suitable for ruling-in/out acute myocardial infarction and for risk stratification in this acute setting [4,5,6,7]
Abbott hs-cTnI in samples with C-reactive protein (CRP) ≥ 90 mg/L, whereas a correlation was evident in samples collected in the presence of possible autoimmune diseases and poor renal function (Figure 1A)
Recovery of CRP ranged from −15% to 10% after mixing with a high coefficient of determination (R2 = 0.99), with hs-cTnI recovery lower at −12% to −66%, with three samples yielding recoveries of −61%, −62%, −66% (R2 = 0.40), suggesting an interference being present (Figure 1B)
Summary
The latest hs-cTnI assay to obtain regulatory approval (in 2019) outside the United States which is available on large, integrated core laboratory instruments (i.e., chemistry and immunoassay testing) is the Ortho Clinical Diagnostics hs-cTnI assay, with both clinical and analytical performance data recently published [8,9,10,11,12,13,14]. Data on assay performance outside carefully conducted clinical and analytical studies are important. This real-world data indicates a higher imprecision with the Ortho hs-cTnI assay (i.e., imprecision as assessed via the coefficient of variation; CV) which may limit its use for sites using the proposed
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