Summary

Evaluation of the accuracy of ultrasound has yielded heterogeneousresults. Our objective was to summarize the evidence onthe accuracy of ultrasound compared to venography in asymptomaticpatients, taking into account the variation due tothreshold differences. Searches of journal table of contents,computer databases (Medline, Embase, Biomed, Cochrane) andconference proceedings were performed. A study was eligible ifit prospectively compared ultrasound to venography for thediagnosis of DVT in asymptomatic patients. Data of studiesselected for inclusion were extracted independently by twoauthors. High quality studies with consecutive patient enrollment,blind evaluation of the two techniques, and absence ofverification bias are summarized as Level 1, while those not fulfillingone or more of these criteria are considered Level 2.Original study authors were contacted to confirm accuracy andto provide missing data. A pooled estimate of the accuracy of ultrasound was obtained according to the method of Mosesand coworkers. This method gives a summary diagnostic oddsratio (DOR).The DOR is a single indicator of test performance.It varies between 0 and infinity and exceeds 1, only when ultrasoundis more often positive in patients with DVT relative tothose without DVT. Higher DOR indicates better discriminatorytest performance.Thirty one studies were rated as potential-lyunbiased and graded as Level 1.The mean prevalence of DVTas determined by venography was 22%. In Level 1 studies, theodds of positive ultrasound in proximal veins was 379 timeshigher (95% confidence limits 65, 2,200) and in distal veins 32times higher (7.5, 135) among patients with DVT than thosewithout. Our results suggest that, particularly for proximalveins, ultrasound is accurate for the diagnosis of DVT in asymptomaticpostoperative orthopedic patients. More research isneeded in other clinical settings.