NEW YORK (Reuters Health) – Rates of deep vein thrombosis (DVT) in immobilized stroke patients are lower when thigh-length graduated compression stockings are used rather than below-knee stockings, a multicenter team reports.

While below-knee stockings are more widely used than the thigh-length stockings, there’s no good evidence that the short versions are as effective for DVT prophylaxis, the researchers explain in the Annals of Internal Medicine published online September 21.

Dr. Martin Dennis with the University of Edinburgh, Western General Hospital, UK and colleagues conducted a randomized comparison trial of below-knee and thigh-length compression stockings involving 3114 immobile patients hospitalized with acute stroke in 112 hospitals in 9 countries.

Randomization was not blinded, as the nature of the assigned device was pretty obvious.

“Ultrasonographers performed compression duplex ultrasonography in 1406 patients (96% of the survivors) in each treatment group between 7 and 10 days after enrollment,” according to the report. Somewhat fewer than half the patients had a second scan about 4 weeks later.

The primary endpoint, either a symptomatic or asymptomatic DVT in the popliteal or femoral veins, occurred in 98 of 1552 patients (6.3%) who received thigh-length stockings and in 138 of 1562 (8.8%) who received below-knee stockings, the researchers found. The 2.5-percentage point difference (P= 0.007) translates to a 31% difference in odds.

Thigh-length stockings were removed more often because of concerns about the skin or patient comfort issues, but 75% of patients in both groups wore the stockings until they were discharged, died, or regained their mobility or for 30 days.

Despite the statistical reduction in risk of DVT with thigh-length stockings, the authors conclude in their discussion of the results and other related studies “that thigh-length stockings are unlikely to have clinically important benefits for patients with stroke.”

Nevertheless, the 2.5-percentage point reduction in absolute risk suggests “a potentially substantial effect on public health” since a large number of hospitalized patients in categories other than stroke are fitted with stockings to prevent DVT.

Ann Intern Med 2010;