The interobserver reliability of a novel qualitative point of care assay for heart-type fatty acid binding protein.

Background: Heart-type fatty acid-binding protein (h-FABP) may help to improve the early diagnosis of acute coronary syndromes in patients presenting to the Emergency Department (ED) with chest pain. A novel qualitative point of care h-FABP lateral flow immunoassay (True Rapid, FABPulous BV) could provide results to clinicians within just 5min. Given the qualitative nature of this test and prior to evaluation in a large diagnostic study, we aimed to determine inter-observer reliability when interpreted contemporaneously by staff in the ED.

Methods: In a nested prospective cohort study including adult patients with suspected cardiac chest pain, venous blood samples were tested for h-FABP (FABPulous BV) on arrival and 3h later. Each test result was independently interpreted by two different investigators after 5min. The investigators were blinded to each other's interpretation and recorded their findings on separate case report forms. We determined interobserver reliability by calculating the Cohen's kappa score and 95% confidence intervals.

Results: A total of 43 test results (from 31 patients) were each interpreted by two independent investigators. Absolute agreement between investigators was 93.0%, with a Cohen's kappa of 0.81 (95% CI 0.6-1.0), indicating near perfect agreement. In total there were three (7.0%) disagreements. In each case one investigator reported a 'weak positive' result while the other interpreted the result as 'negative'.

Conclusions: These findings demonstrate the interobserver reliability of a qualitative point of care h-FABP assay. Further work must evaluate diagnostic accuracy and determine the clinical implications of the small rate of disagreement.