The two-point compression ultrasound exam assesses the lower extremity venous system at two points: common femoral vein and popliteal vein. Signs of DVT include lack of compressibility and visualized thrombus.
Several studies have looked at the accuracy of ultrasound performed by emergency physicians. Results are variable but overall shows good accuracy.
-One prospective cross-sectional study  compared EP-performed two-point ultrasound and Radiology Dept ultrasound. 47 different EPs at various training levels performed a total 199 studies, 45 studies were positive for DVT. Results: Sensitivity 100% (95%CI 92-100%), specificity 99% (95%CI 96-100%).
-Another Prospective single center study  compared EP-performed three-point ultrasound and Radiology Dept whole-leg ultrasound. A total 183 patients were studied with 27 (15%) positive for DVT. Results: Sensitivity 70% (95% CI 60-80%), Specificity 89% (95% CI 83-94%)
-A systematic review  of EP-performed study had a total of 936 patients and showed overall sensitivity 95% (95% CI 87-99%) and specificity 96% (95%CI 87-99%).
2. Crisp JG, Lovato LM, Jang TB. Compression ultrasonography of the lower extremity with portable vascular ultrasonography can accurately detect deep venous thrombosis in the emergency department. Ann Emerg Med. 2010 Dec;56(6):601-10.
3. Kline JA, O’Malley PM, Tayal VS, Snead GR, Mitchell AM. Emergency clinician-performed compression ultrasonography for deep venous thrombosis of the lower extremity. Ann Emerg Med.2008 Oct;52(4):437-45.