Background: Acute aortic dissection (AAD) with concurrent ST-segment elevation myocardial infarction (STEMI) is relatively rare and sometimes overlooked. As D-dimer testing has been reported to have high sensitivity to diagnose AAD in a clinical scale, Aortic Dissection Detection Risk Score (ADD-RS), a point-of-care D-dimer analyzer capable of measuring in 10 min would be useful to deny AAD with concurrent STEMI. However, an optimal cut-off value of D-dimer in such population remains unclear. Therefore, the aim of this study was to elucidate the optimal D-dimer threshold in patients clinically diagnosed with STEMI. Methods: This retrospective cohort study was conducted at two tertiary care centers between 2014 and 2019. Patients clinically diagnosed with STEMI who underwent serum D-dimer measurement on hospital arrival were included. The primary outcome was the diagnosis of AAD. The area under the receiver operating characteristic curve (AUROC) for D-dimer values to diagnose AAD was evaluated, particularly in patients with low to moderate risks of AAD (1 of ADD-RS). The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were calculated with several cut-off values. Results: A total of 322 patients were included, and 28 were diagnosed with AAD. The AUROC for D-dimer to diagnose AAD was 0.970 (95% confidence interval: 0.948–0.993) in 262 patients with 1 of ADD-RS. If D-dimer ≥750 ng/mL was used as a cut-off value, sensitivity, specificity, PPV and NPV were 100%, 86.4%, 37.7%, and 100%, respectively. AAD could be denied in 209 (79.8%) patients using the cut-off value (D-dimer <750 ng/mL). Conclusions: Serum D-dimer ≥750 ng/mL exhibited high sensitivity and NPV to diagnose AAD with concurrent STEMI, while the ADD-RS originally utilized ≥500 ng/mL as a cut-off for any suspected AAD. A point-of-care D-dimer measurement with the new cut-off would be useful to rule-out AAD among patients with STEMI.
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