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Pulmonary embolism in patients with intermediate probability lung scans: diagnosis with Doppler venous US and D-dimer
R J Quinn1, R Nour, S P Butler
1Department of Nuclear Medicine, St George Hospital, Kogarah, New South Wales, Australia.
Purpose:
To test the usefulness of lower limb Doppler venous compression ultrasound (US) and serum D-dimer measurements in diagnosis of pulmonary embolism in patients in whom ventilation-perfusion (V-P) scans indicate intermediate probability of pulmonary embolism.
Materials And Methods:
V-P scanning, pulmonary angiography, US, and D-dimer measurements were performed in 36 patients without known deep venous thrombosis but with intermediate probability of having a pulmonary embolism.
Results:
Pulmonary angiography demonstrated pulmonary embolism in 15 (41%) of 36 patients. US demonstrated deep venous thrombosis in only two patients, both with pulmonary embolism. Sensitivity of US was only 13%, but specificity was 100%. Five (14%) of the 36 patients had normal (< 220 micrograms/L) D-dimer levels; none of the five had pulmonary embolism. Sensitivity and specificity of D-dimer values were 100% and 16%, respectively, with a negative predictive value of 100%.
Conclusion:
Combined D-dimer measurement and US were helpful in correctly diagnosing pulmonary embolism in only seven (20%) of 36 patients. Pulmonary angiography is still required to diagnose pulmonary embolism in the majority of patients.