Normal D-Dimer Concentration in Hospitalized Patients with Lung Diseases

Introduction: D-dimer testing is an established method in diagnostics of suspected pulmonary embolism (PE). However, in hospitalized patients, increased D-dimer concentration may be caused by comorbidities, which limits the applicability of this test in PE diagnostics. According to published data, calculating the index D-dimer/fibrinogen ratio can increase specificity of D-dimer testing in diagnostics of venous thromboembolism (VTE). The aim of the present study was: (1) to determine the frequency of normal D-dimer concentration in hospitalized patients with lung diseases in whom the differential diagnostics of PE can be particularly difficult; and (2) to evaluate the utility of D-dimer/fibrinogen ratio in subgroups of patients with acute VTE or with lung cancer. Materials and methods: The study group included 619 consecutive patients aged 54.9 (±15.4) years, hospitalized in a pulmonology reference centre. Among them there were 96 (15%) patients with acute VTE, 65 (10%) with exacerbation of COPD, and 172 (27%) with lung cancer. Results: Mean D-dimer concentration (Vidas D-dimer New) was 1956 ± 3691 ng/mL and median value was 842 (45–35,678) ng//mL. Normal D-dimer concentration (<500 ng/mL) was found in 225/523 (43%) patients without acute VTE. In 49% (32/65) patients with COPD and in 25% (43/172) patients with lung cancer, D-dimer concentration was below 500 ng/ml. Ddimer/ fibrinogen ratio was significantly higher in acute VTE patients compared to lung cancer patients (808 ± 688 and 289 ± 260, respectively; p < 0.001). Conclusions: Normal D-dimer concentration was found in more than 40% of patients with lung diseases hospitalized in the reference pulmonology centre. This observation can suggest a better utility of D-dimer measurement for PE exclusion in such a population than that seen in previously published reports. D-dimer/fibrinogen ratio is significantly higher in acute VTE than in lung cancer, but the clinical value of this test requires further evaluation.