D-dimer for myocardial infarction diagnosis in patients with acute coronary syndrome admitted to a chest pain unit

Background

D-dimer (Dd) is a thrombosis marker and is a well-established test for venous thromboembolism but its use for acute coronary syndromes (ACS) has few studies. We evaluated the accuracy of Dd for diagnosing non-ST-segment elevation myocardial infarction (NSTEMI).

Methods

From January 2002 to December 2003, 531 patients were admitted to a chest pain unit (67.4 ± 13.5 years; 294 [55.4%] male) with probable ACS. Dd, electrocardiogram (EKG) and troponin I (TnI) were systematically performed at admission, whereas EKG and TnI were repeated 6 hours later. NSTEMI criteria were TnI ≥ 1.0 ng/ml at any moment combined with the absence of ST elevation. The chi-square test evaluated the association between NSTEMI and positive Dd (≥ 500 ng/ml). We evaluated the operational characteristics of this diagnostic test as well.

Results

Eighty-one (15.3%) patients met NSTEMI criteria. Overall, Dd was positive in 218 patients, from which 47 (21.6%) had NSTEMI. For the diagnosis of NSTEMI, Dd has shown a 58% sensibility, 62% specificity, 21.6% positive predictive value and 89.1% negative predictive value, resulting in 51.4% global accuracy. The positive likelihood ratio was 1.53 and the negative likelihood ratio was 0.68.

Conclusion

Dd can be useful for NSTEMI exclusion as part of a chest pain unit routine blood sample protocol.