Value of diagnostic tests for deep venous thrombosis: a decision analysis model

A decision analysis model and data pooled from more than 12,000 patients were used to help elucidate conflicting results about the preferred method for diagnosing deep venous thrombosis (DVT). The prevalence of DVT in symptomatic legs is 40%, a value at which venography followed by Doppler ultrasound (in cases of nondiagnostic or unsuccessful venography) is preferred over the sequence of Doppler-plethysmography, provided that the sensitivity of the latter is less than 94%. If the prevalence of DVT decreases to 25% or the sensitivity of Doppler is 95% or higher, then the sequences of Doppler-plethysmography and venography-Doppler are equivalent in helping minimize resulting morbidity and mortality. Because of the greater clinical significance of proximal DVT, the analysis was modified to reflect changes in prevalence, sensitivity of noninvasive tests, and rate of pulmonary embolus due to DVT extending above the knee. In this case, performing plethysmography is slightly better than performing venography followed by Doppler or plethysmography.