High sensitivity with color duplex sonography in thrombosis screening after ankle fracture surgery.

BACKGROUND

Phlebography is regarded as the reference standard for diagnosing asymptomatic deep vein thrombosis (DVT) in studies of thromboprophylaxis. However, technical advances with noninvasive color duplex sonography (CDS) have made this procedure an interesting alternative.

OBJECTIVES

The objective of the present prospective study was to compare the sensitivity and specificity of CDS with those of phlebography.

PATIENTS

The first 180 consecutive patients included in a larger randomized trial for prolonged thromboprophylaxis were subject to unilateral CDS and to phlebography after ankle fracture surgery. The patients were examined 6 weeks after surgery, all examinations being evaluated blindly. After patient drop outs and exclusions, 144 patients were left for analysis.

RESULTS

Phlebography and CDS examinations were inconclusive or were not completed for 19% of these patients (28/144). DVT was diagnosed by phlebography in 21% (24/116) of the remaining patients. Most of the thrombi were isolated calf DVTs (18/24). In contrast, DVT was diagnosed by CDS in 31% of these patients (36/116): only one case diagnosed by phlebography was missed by CDS. The specificity of CDS is thus 86% and its sensitivity is 96%. The positive predictive value is 64%, and the negative predictive value is 99%.

CONCLUSIONS

CDS is a safe method for detecting asymptomatic distal DVT. It has a high sensitivity and high negative predictive value, which means that the method is highly reliable to rule out DVT. Our results indicate that CDS could be considered as an alternative method for DVT screening.