ACCURACY OF CLINICAL-ASSESSMENT OF DEEP-VEIN THROMBOSIS

The clinical diagnosis of deep-vein thrombosis is generally thought to be unreliable, From experience, we hypothesised that this widely held view might be incorrect. We developed a clinical model and prospectiv ely tested its ability in three tertiary care centres to stratify symp tomatic outpatients with suspected deep-vein thrombosis into groups wi th high, moderate, or low probability groups of deep-vein thrombosis. We evaluated our clinical model in combination with venous ultrasonogr aphy to determine the potential for an improved and simplified diagnos tic approach in patients with suspected deep-vein thrombosis. All pati ents were clinically assessed to determine the probability for deep-ve in thrombosis before they had ultrasonography and venography. All test s were performed and interpreted by independent observers, In 529 pati ents, the clinical model predicted prevalence of deep-vein thrombosis in the three categories: 85% in the high pretest probability category, 33% in the moderate, and 5% in the low category. There was no statist ical difference in the performance of the model in the three centres. The model demonstrated excellent interobserver reliability (Kappa=0.85 ), There were important differences with ultrasonography between the h igh and low pretest probability groups for both positive predictive va lues (100% (95% CI, 94-100%) vs(63% [35-85%], respectively). Thus, use of the clinical model combined with ultrasonography would decrease th e number of false positive and negative diagnosis if venography were d one when the ultrasound result and pretest probability were discordant . The diagnostic process could be simplified by excluding those patien ts with low pretest probability and normal ultrasound results from ser ial testing.