Discordant diagnoses of acute myocardial infarction due to the different use of assays and cut-off points of cardiac troponins.

OBJECTIVES

Several assays for the measurement of cardiac troponin (cTn) are available, but differences in their analytical performances may affect the diagnosis of acute myocardial infarction (MI).

METHODS

A survey was conducted at all Danish departments of clinical biochemistry at hospitals receiving patients with suspected acute MI to gather information about the assay and cut-off value used. cTn was measured in blood samples from 574 patients enrolled into the Odense Chest Pain Biobank with 3 different assays: the 4th generation cTnT (cTnT(4th)), high-sensitivity cTnT (cTnT(hs); Roche Diagnostics) and cTnI (Abbott Diagnostics). To evaluate concordance, patients were dichotomised according to the 99th percentile value for each assay. Additionally, a cut-off at 50 ng/l for cTnT(hs) was used, as this is the currently employed cut-off point in Denmark.

RESULTS

Using a cTnT(4th) cut-off value of >0.03 µg/l, 130 patients (23%) had potential MI. With the cTnT(hs) assay and cut-off values at 50 versus 14 ng/l, respectively, 136 (24%) versus 301 (52%) patients had potential MI. With the cTnI cut-off point, 205 patients (36%) should be considered as having had an acute MI.

CONCLUSIONS

The use of different cTn assays and cut-off values may result in a discordant frequency of MI diagnoses. This makes efforts to harmonize cTn assays and cut-off levels mandatory.