Regular paper
Differences in the diagnosis of myocardial infarction by troponin T compared with clinical and epidemiologic criteria

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Abstract

We investigated the difference in the number of myocardial infarction (MI) diagnoses based on troponin T compared with clinical and epidemiologic (modified FINnish Multinational MONItoring of trends and determinants in CArdiovascular diseases) diagnoses, and the prognosis of patients with discordant diagnoses. Five hundred fifty-nine consecutive patients (315 men and 244 women, median age 69 years) were admitted to the hospital with a suspected acute coronary syndrome. Median follow-up time was 17 months. Of the 559 patients, 127 had a clinical and 137 an epidemiologic diagnosis of MI. When a diagnosis of MI was primarily based on troponin T (>0.10 μg/L), the number of MIs was 169, which increased by 33% compared with the number of MIs by clinical diagnosis, and by 23% compared with those by epidemiologic diagnosis. However, troponin T was not elevated in 13% of the 127 patients with the clinical diagnosis and in 14% of the 137 patients with the epidemiologic diagnosis of MI. Among patients in whom clinical diagnosis of MI was not made, the prognosis with regard to coronary death or nonfatal MI was not significantly worse in patients with troponin T >0.10 μg/L than ≤0.10 μg/L (hazard ratio 1.07; 95% confidence interval 0.62 to 1.84). In patients with a suspected acute coronary syndrome, troponin T-based diagnostics leads to an increase in the number of patients diagnosed with MI compared with clinical or epidemiologic diagnosis. The prognostic impact of troponin T in patients without clinical diagnosis of MI based on elevations in conventional enzyme activities needs further study in larger series of patients.

Section snippets

Patients

During the study period (from August 30, 1995, until February 29, 1996), 646 patients with a suspected acute coronary syndrome were admitted to the emergency department of the Kuopio University Hospital. Twenty-two surviving patients were excluded either because of a premature discontinuation of the study protocol (difficulties in drawing a blood sample, returning home after only 1 sample, or transfer to other hospital department) or because of missing biochemical marker measurements. Of the

Comparison of diagnostic classifications

Of the 559 patients, 127 (23%) had a clinical diagnosis of MI. If diagnosis of MI was based on elevated troponin T (>0.10 μg/L), the number of MIs increased up to 169, by 33% compared with a clinical MI diagnosis. Seventeen patients (13%) in whom MI was diagnosed clinically had troponin T ≤0.10 μg/L. Of these 17 patients, 4 (24%) had ST-segment or T-wave changes on the ECG, and 4 (24%) had conventional enzyme activity >1 and ≤2 × the upper reference limit. Ten of the 17 patients (59%) had a

Discussion

Our study of consecutive patients admitted to the hospital with a suspected acute coronary syndrome showed that the diagnosis of MI made on the basis of increased serum troponin T concentration (>0.10 μg/L) increased the total number of patients receiving the diagnosis of MI by 33% compared with the clinical diagnosis, and by 23% compared with the standardized epidemiologic diagnosis. However, there was some crossover to the other direction between the diagnostic classifications; troponin T

Acknowledgements

We thank the personnel of the Accident and Emergency Department and the Department of Clinical Chemistry of the Kuopio University Hospital for their skillful work during the study. We also thank Pertti Palomäki, MD, and Jouko Remes, MD, for their collaboration in the early phases of this study, and Heikki Miettinen, MD, and Veikko Salomaa, MD, for comments on this text.

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    This study was supported by grants from the Finnish Foundation for Cardiovascular Research, the University of Kuopio and the Kuopio University Hospital, Kuopio, Finland

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