KM Sam^1,2, QT Lam¹, HG Schneider^1,3

1 Clinical Biochemistry Department, Alfred Pathology Service, Alfred Health, Melbourne, Australia; 
2 School of Clinical Science, Monash University, Clayton, Australia; 
3 Department of Epidemiology and Preventative Medicine, Monash University, Melbourne, Australia;

Cardiac troponin measurement is essential in chest pain pathways to diagnose acute myocardial infarction (AMI) but its use can be challenging due to non-AMI causes of elevation. In 2022, Eggers et al. reported hsTnI/T ratio as a useful marker for early diagnosis of type 1 MI (MI1). We retrospectively reviewed 205 adult patients presenting over 3 months (30.08.2019 to 30.11.2019) with symptoms suggestive of AMI and paired hsTnI (Abbott Alinity-i STAT hsTroponin-I) and hsTnT (Roche e411 TroponinT hs) performed in real time. MI1 was defined by the 4th Universal Definition. Other patients were classified as non-MI1. In this cohort, review of clinical information determined 84 (40.9%) as MI1 patients. A hsTnI/T ratio of ≥2.0 provided sensitivity 69%, specificity 55%, positive likelihood ratio of 1.52 with overall accuracy of 61% to diagnose MI1. The receiver operating characteristics area under the curve (AUC) for our cohort was 0.673. Compared to the previously reported AUC of 0.89, our study shows lower utility of the hsTnI/T to differentiate MI1 from non MI1, instead calling for further investigation with prospective research studies.