A systematic review of the accuracy of ultrasound in the diagnosis of deep venous thrombosis in asymptomatic patients

Abstract

Evaluation of the accuracy of ultrasound has yielded heterogeneous results. Our objective was to summarize the evidence on the accuracy of ultrasound compared to venography in asymptomatic patients, taking into account the variation due to threshold differences. Searches of journal table of contents, computer databases (Medline, Embase, Biomed, Cochrane) and conference proceedings were performed. A study was eligible if it prospectively compared ultrasound to venography for the diagnosis of DVT in asymptomatic patients. Data of studies selected for inclusion were extracted independently by two authors. High quality studies with consecutive patient enrollment, blind evaluation of the two techniques, and absence of verification bias are summarized as Level 1, while those not fulfilling one or more of these criteria are considered Level 2. Original study authors were contacted to confirm accuracy and to provide missing data. A pooled estimate of the accuracy of ultrasound was obtained according to the method of Moses and coworkers. This method gives a summary diagnostic odds ratio (DOR). The DOR is a single indicator of test performance. It varies between 0 and infinity and exceeds 1, only when ultrasound is more often positive in patients with DVT relative to those without DVT. Higher DOR indicates better discriminatory test performance. Thirty one studies were rated as potentially unbiased and graded as Level 1. The mean prevalence of DVT as determined by venography was 22%. In Level 1 studies, the odds of positive ultrasound in proximal veins was 379 times higher (95% confidence limits 65, 2,200) and in distal veins 32 times higher (7.5, 135) among patients with DVT than those without. Our results suggest that, particularly for proximal veins, ultrasound is accurate for the diagnosis of DVT in asymptomatic postoperative orthopedic patients. More research is needed in other clinical settings.

Tissue factor expression as a possible determinant of thromboembolism in ovarian cancer

“…Our study, however, focused on asymptomatic DVT patients and symptomatic DVT occurred in just three patients of the 32 patients, compared with asymptomatic DVT in seven of 32 patients. Symptomatic DVT patients have been known to be objectively far less common than in screening tests including asymptomatic DVT patients (Kassaï et al, 2004). Girard et al (1999) reported that 82% of patients with acute PTE still displayed detectable residual DVT at the time of PTE diagnosis, and DVT remains asymptomatic in nearly two-thirds of PTE patients.…”

Literature search parameters marginally improved the pooled estimate accuracy for ultrasound in detecting deep venous thrombosis

“…Of the 45 studies, 42 were published in English, 2 in French [35,36], and 1 in Italian [37]. Detailed results of this meta-analysis are published elsewhere [38]. One article was missed when only the Medline database was searched, and one level 1 and three level 2 studies were missed when the Medline search was limited to English-language articles.…”

The true treatment benefit is unpredictable in clinical trials using surrogate outcome measured with diagnostic tests

“…Nonetheless, the difficulty inherent in the evaluation of diagnostic tests and lack of reliable studies make any adjustment impossible. Systematic review of diagnostic tests could gainfully be used to evaluate the quality and summarize the accuracy of potentially unbiased studies with appropriate meta-analytic methods [65]. Unfortunately, as shown by recent metaanalyses, most studies are potentially biased or do not report in sufficient detail patient or study features that might influence diagnostic accuracy.…”