Diagnostic value of D-dimer measurement in patients referred to the emergency department with suspected myocardial ischemia

Background The accurate identification of patients with acute myocardial infarction ( AMI) remains one of the most difficult challenges facing emergency physicians. The introduction of early and reliable biomarkers of AMI should hence be acknowledged, since they would increase the efficiency of the diagnostic process. Methods A total of 2,276 consecutive patients referred to the emergency department for clinical symptoms suggestive for AMI underwent cardiac troponin T (cTnT) and D-dimer testing between January and December 2006. Patients sample were eligible for inclusion in this investigation if they had been collected prior to medication or intervention and 12-24 h after the time of patient's arrival to the emergency department, when the diagnostic efficiency of cTnT is the highest. cTnT was assayed on the Elecsys 2010 and test results were stratified according to the decisional threshold corresponding to the lowest TnT concentration associated with a 10% total imprecision in the assay (> 0.03 mu g/l). Plasma D-dimer was measured employing Vidas DD. Results The results of 741 patient's samples fulfilled the above criteria and were included in the study, 252 (34%) of whom had cTnT values > 0.03 mu g/l. The D-dimer value distribution ( median and 95% C.I.) was significantly different in patients with cTnT values > 0.03 mu g/l than in those with cTnT values < 0.03 mu g/l (2,227 mu g/l, 431-10,000 mu g/l versus 1,039 mu g/l, 143-6,338 mu g/l; P < 0.001). The area under the receiver operating characteristic ( ROC) curve, was 0.734 (95% confidence interval: 0.715-0.753; P < 0.001). At the 500 mu g/l diagnostic threshold estimated by the ROC curve analysis, corresponding to the cut- off for the diagnosis of VTE, sensitivity and specificity of Vidas D-dimer were 95% and 27%, respectively. The positive and negative predictive values were estimated as 92% and 41%, respectively. In linear regression analysis, no significant association (r = 0.090; P = 0.077) was observed between D-dimer and cTnT in patients with cTnT levels exceeding the decisional threshold of the assay. Conclusions Results of the present investigation on patients with AMI established by accepted diagnostic criteria (cTnT values above the decisional threshold of the assay associated with suggestive clinical symptoms), testify that D-dimer testing would not add clinically meaningful information to the sole determination of the cardiospecific troponins 12 - 24 h after patient's admission at the emergency department, when the cumulative data indicate that the diagnostic efficiency of cTnT is the highest.