The Usefulness of the Combination of D-Dimer and Soluble Fibrin Monomer Complex for Diagnosis of Venous Thromboembolism in Psychiatric Practice: A Prospective Study

PURPOSE: D-dimer has the advantage of excluding venous thromboembolism (VTE) due to its high sensitivity but is disadvantageous for diagnosing VTE due to its low specificity. A method to increase the usefulness of D-dimer in the diagnosis of VTE is warranted. This study aimed to investigate the usefulness of the combination of D-dimer and soluble fibrin monomer complex (SFMC), which has been suggested as a new candidate marker for VTE, in VTE diagnosis. PATIENTS AND METHODS: This prospective study in 109 subjects was performed at a psychiatric department between August 1, 2017 and December 31, 2019. Subjects’ levels of D-dimer and SFMC were measured simultaneously. Plasma levels of D-dimer and SFMC were measured using NANOPIA(®) D-dimer and NANOPIA(®) SF. Subjects with positive D-dimer (≥1.0 µg/mL) results underwent contrast computed tomography for confirmation of VTE within 12 hours of D-dimer measurement. A receiver operating characteristic curve analysis was performed to examine the usefulness of SFMC for the diagnosis of VTE. RESULTS: Only 109 of the 783 subjects without symptoms suggestive of VTE participated in the study. Out of 41 subjects with positive D-dimer results, 17 subjects were diagnosed with VTE. A receiver operating characteristic curve analysis was performed to determine cutoff values. The area under the curves was 0.848 for SFMC (p<0.001, 95% CI 0.722 to 0.974), and the optimal cutoff value was 10.0 µg/mL (sensitivity 58.8%, specificity 100%, positive predictive value 100%, negative predictive value 77.4%). CONCLUSION: SFMC was useful for diagnosing VTE in the psychiatric patients with positive D-dimer results.