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

Qualitative analysis of D-dimer, i.e., a fibrin degradation product, is important in excluding pulmonary thromboembolism (PTE) or deciding advanced methods for diagnosis. But it is not still well known that quantitative analysis of D-dimer has a role in differential diagnosis of other diseases that cause positive D-dimer levels. Besides it is also uncertain that the follow up of D-dimer levels has a role in PTE.In this study; it was aimed to identify the value of quantitative D-dimer levels in differential diagnosis of PTE and community acquired pneumonia (CAP) and to determine the alteration in D-dimer levels during anticoagulant treatment. It was also aimed to evaluate the effect of this alteration to severity and recurrence of PTE.A total of 80 patients were included for the study. Study was continued with 45 PTE patients and 35 CAP patients. Serum D-dimer levels were measured with latex added immunoturbidometric method, named as D-Dimer plus, at first during admission before initiating any antibiotic or anticoagulant therapy and then at 3rd day, 10th day and 1st month of treatment. The demographic characteristics, risk factors, symptoms and findings of physical examination, laboratory parameters and radiology results were recorded.No recurrence was seen at the end of 1st year follow up period among the patients who completed their anticoagulant therapy for PTE. Patients with CAP were discharged at mean 10.5 days when their clinic and laboratory parameters were improved by appropriate antibiotic therapy.Mean D-dimer levels at admission (day 0) were found significantly higher in PTE patients than CAP patients.When the % changes in D-dimer levels with time were compared it was again statistically significantly higher in PTE group. ROC curve analysis was used to determine the cut-off value for D-dimer levels at admission. D-dimer level > 1700 µ/L was found statistically significant as a cut- off value for the diagnosis of PTE.After the initiation of anticoagulant therapy a significant decrease in D-dimer levels was identified in PTE group but not in CAP group. We hypothesized that recurrence can be seen after completion of anticoagulant therapy in PTE but no recurrence was found in this study.These results pointed out that quantitative serum D-dimer levels at admission could be used in differential diagnosis of PTE and CAP. Since it shows rapid decrease in PTE patients under anticoagulant therapy than CAP patients, D-dimer levels can be used for differential diagnosis and confirmation of PTE.