Diagnostic performance of a high-sensitive troponin T assay and a troponin T point of care assay in the clinical routine of an Emergency Department: A clinical cohort study.

BACKGROUND: A point of care test (POCT) for troponin T (TnT) in the Emergency Department (ED) was compared to a high-sensitivity TnT (hsTnT) central laboratory test (CLT) to determine the influence of test system and different cut-off values on the diagnostic performance in patients with suspected acute coronary syndrome (ACS) under routine conditions.

METHODS: All patients with routine TnT testing in the ED were enrolled. Only internal medicine patients without STEMI and with both troponin values were analyzed. TnT was measured with a contemporary sensitive POCT assay in the ED and with a hs-assay in the central laboratory. The diagnostic performance was analyzed at two different cut-off points (99th percentile and conventional rule-in cut-offs). Primary endpoint was the diagnosis of NSTEMI.

RESULTS: Of all patients (n=3423), 3.6% had a diagnosis of NSTEMI (n=124). For the hsTnT assay, 28.4% of all values were at or below the lower limit of detection (LOD) as compared to 75.7% of the POC-TnT-values. The area under the receiver operating curves did not differ significantly between the assays (hsTnT: 0.912(95%-CI: 0.884-0.940); POC-TnT: 0.896(95%-CI: 0.859-0.933)). The diagnostic performance was very similar for both assays: the positive predictive value was below 50% for troponin values below 100ng/L and hardly increased for values between 100 and 600ng/L for hs and conventional assays.

CONCLUSIONS: In our cohort of emergency patients, the diagnostic performance of conventional POC-testing was comparable to hsTnT. A 99th percentile cut-off may be useful for rule-out of NSTEMI, but seems limited for routine rule-in strategies.