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Association between pulmonary microthromboembolism and coagulation variables in hypercoagulable states: an autopsy
1Department of Respiratory Medicine, Showa University Fujigaoka Hospital, Yokohama City, Japan. asahi-hp@lares.dti.ne.jp
Objective:
This autopsy study was carried out to investigate the relationship between the number of pulmonary microthromboemboli and coagulation tests in patients with coagulation abnormalities.
Methodology:
Fifty-one patients in whom coagulation studies were performed within 2 days prior to death were studied. The coagulation tests included platelet counts, prothrombin times expressed as International Normalized Ratios (INR), activated partial thromboplastin times, fibrinogen concentrations, plasma fibrinogen/fibrin fragment E antigen levels, and plasma D-dimer levels. For microscopic analysis, five tissue blocks of the lung were taken from each subject and the number of pulmonary microthromboemboli per 20 cm2 of tissue sections was calculated.
Results:
Thirty-six of the 51 patients had pulmonary microthromboembolism. International Normalized Ratios were higher than 1.7 in 12 of 36 embolic and in two of 15 non-embolic patients (33.3% of sensitivity and 86.7% of specificity). There was no significant difference in D-dimer levels between the two groups. Multiple regression analysis identified that INR was significantly related to the number of microthromboemboli (P = 0.042).
Conclusions:
D-dimer levels appear to be inappropriate as a single screening test for disseminated intravascular coagulation (DIC) in critically ill patients because the levels in these subjects are elevated irrespective of the presence of microthromboemboli. Because of the high specificity, INR could be a specific marker for microthromboemboli. The significant association between the number of microthromboemboli and INR might indicate the importance of the extrinsic pathway in the initiation of DIC.