A national survey of practice patterns in the noninvasive diagnosis of deep venous thrombosis

Purpose: Recent studies have recommended unilateral venous duplex scanning for the diagnosis of deep venous thrombosis (DVT) in patients who are unila terally symptomatic. Vascular laboratory accreditation standards, however, imply that bilateral leg scanning should be performed. We examined whether actual practice patterns have evolved toward limited unilateral scanning in such patients. Methods: A questionnaire was mailed to all 808 vascular laboratories in the United States that were accredited by the Intersocietal Commission for the Accreditation of Vascular Laboratories (ICAVL). To encourage candid respon ses, the questionnaires were numerically coded and confidentiality was assu red. Results: A total of 608 questionnaires (75%) were completed and returned. M ost of the respondents (442; 73%) were either, community-hospital or office -based laboratories, and the remaining 163 (27%) were university or affilia ted-hospital laboratories. Most of the laboratories (460; 76%) had been in existence for 9 years or more, and 65% had been ICAVL-accredited in venous studies for 3 years or more. Board-certified vascular surgeons were the med ical directors in 54% of the laboratories. Duplex ultrasound scanning was t he diagnostic method used by 98% of the laboratories. In patients with unil ateral symptoms, 75% of the laboratories did not routinely scan both legs f or DVT. A large majority (75%) believe that bilateral scanning is not clini cally indicated. Only 57 laboratories (14%) recalled having patients return with a DVT in the previously unscanned leg, with 93% of these laboratories reporting between one and five such patients. This observation correlated with larger volumes of venous studies performed by those laboratories (P < .05). Similarly, only 52 laboratories (12%) recalled having patients return with subsequent pulmonary emboli. Of these laboratories, only five reporte d proximal DVT in the previously unscanned legs of such patients. Of all th ese laboratories, therefore, only 1% (5 of 443) have potentially missed the diagnosis of a DVT that caused a preventable pulmonary embolus with such a policy. Among those laboratories that always perform bilateral examination s, 41% do so because of habit. Most (61%) of the laboratories that perform bilateral scanning would do unilateral scanning if it were specifically app roved by ICAVL. Conclusion: Three quarters of the ICAVL-accredited vascular laboratories pe rform limited single-extremity scanning for the diagnosis of DVT in patient s with unilateral symptoms. This broad clinical experience suggests that th is practice is widespread in selected patients. Clinical protocols should b e established to provide guidelines for local laboratory implementation.