The role of quantitative D-dimer levels in the follow-up and differential diagnosis of pulmonary thromboembolism and community-acquired pneumonia

Aim: To identify the quantitative D-dimer levels in pulmonary thromboembolism (PTE) and hospitalized-community acquired pneumonia (CAP) patients, and to determine the alteration of D-dimer levels with anticoagulant or antibacterial therapy. It is not well known that the quantitative analysis of D-dimer has a role in the differential diagnosis of PTE from other diseases. Materials and methods: Serum D-dimer levels were measured and compared prospectively with a latex-enhanced immunoturbidimetric method at admission, before initiating any antibiotic or anticoagulant therapy and then at days 3, 10, and 30 of treatment in PTE and CAP patients. Results: A total of 80 patients (45 PTE and 35 CAP), with a mean age of 61 ± 16 years, were included in the study. Mean D-dimer levels at admission were significantly higher in the PTE group than in the CAP group (3388 ± 2080 vs. 1190 ± 1089 µ/L, P = 0.001). After initiating the anticoagulant therapy, a significant decrease in D-dimer levels was identified in the PTE group, but not in the CAP group, on day 3 (678 ± 652 µ/L vs. 724 ± 907 µ/L). In the receiver operating characteristic curve analysis, D-dimer levels of >1700 µ/L were statistically significant as a cut-off value for the diagnosis of PTE (AUC: 0.820; 95% CI: 0.73-0.92). Conclusion: Although serum quantitative D-dimer levels cannot be used solely for the differential diagnosis of CAP and PTE, they might be helpful in making the decision to perform further diagnostic methods. Since D-dimer levels decreased more rapidly and significantly in PTE than CAP cases, they might be used as a marker for monitoring the treatment response in patients with PTE, but this must be proven with more comprehensive studies.