Rule out of acute aortic dissection with plasma matrix metalloproteinase 8 in the emergency department

INTRODUCTION: Matrix metalloproteinases (MMPs) are involved in aortic pathophysiology. Preliminary studies have detected increased plasma levels of MMP8 and MMP9 in patients with acute aortic dissection (AAD). However, the performance of plasma MMP8 and MMP9 for the diagnosis of AAD in the emergency department is at present unknown. METHODS: The levels of MMP8 and MMP9 were measured by ELISA on plasma samples obtained from 126 consecutive patients evaluated in the emergency department for suspected AAD. All patients were subjected to urgent computed tomography (CT) scan for final diagnosis. RESULTS: In the study cohort (N = 126), AAD was diagnosed in 52 patients and ruled out in 74 patients. Median plasma MMP8 levels were 36.4 (interquartile range 24.8 to 69.3) ng/ml in patients with AAD and 13.2 (8.1 to 31.8) ng/ml in patients receiving an alternative final diagnosis (P <0.0001). Median plasma MMP9 levels were 169.2 (93.0 to 261.8) ng/ml in patients with AAD and 80.5 (41.8 to 140.6) ng/ml in patients receiving an alternative final diagnosis (P = 0.001). The area under the curve (AUC) on receiver-operating characteristic (ROC) analysis of MMP8 and MMP9 for the diagnosis of AAD was respectively 0.75 and 0.70, as compared to 0.87 of D-dimer. At the cutoff of 3.6 ng/ml, plasma MMP8 had a sensitivity of 100.0% (95% CI, 93.2% to 100.0%) and a specificity of 9.5% (95% CI, 3.9% to 18.5%) and ruled out AAD in 5.6% of patients. Combination of plasma MMP8 with D-dimer increased the AUC on ROC analysis to 0.89. Presence of MMP8 <11.0 ng/ml and D-dimer <1.0 or <2.0 µg/ml provided a negative predictive value of 100% and ruled out AAD in 13.6% and 21.4% of patients respectively. CONCLUSIONS: Low levels of plasma MMP8 can rule out AAD in a minority of patients. Combination of plasma MMP8 and D-dimer at individually suboptimal cutoffs could safely rule out AAD in a substantial proportion of patients evaluated in the emergency department.