Prospective study comparing the rate of deep venous thrombosis of complete and incomplete lower extremity venous duplex ultrasound examinations

Background: A lower extremity venous duplex ultrasound (LEVDUS) examination positive for deep venous thrombosis (DVT) is an indication for anticoagulation. Incomplete examinations that fail to examine all lower extremity veins in patients not otherwise indicated for anticoagulation may be followed by repeated examination to exclude missed or progressing DVT. This study examined the frequency of incomplete LEVDUS studies, reasons for incomplete studies, veins incompletely examined, and follow-up LEVDUS after incomplete LEVDUS. The incidence of a positive finding of DVT was compared between initial complete LEVDUS and follow-up LEVDUS after an initial incomplete examination to determine whether improving rates of follow-up LEVDUS after an incomplete examination is a reasonable target for quality improvement. Methods: At a single academic medical center from January 2017 to December 2017, incomplete LEVDUS studies were prospectively identified in patients who did not otherwise have an identified indication for anticoagulation. Rate of DVT in complete LEVDUS was also determined during the same time frame. Incomplete LEVDUS reports were reviewed for clinical setting, patient demographics, examination indication, ordering providers, reasons for incomplete examinations, anatomic locations of veins not visualized, rates of follow-up LEVDUS examinations within 30 days of the initially incomplete study, and rates of DVT identified in follow-up examinations of initially incomplete examinations. Results: Of the 2843 LEVDUS examinations performed in 2017, 341 studies identified DVT and 197 incomplete examinations did not identify DVT. Veins not visualized on incomplete studies included tibial veins (n = 170 [86.3%]), femoral veins (n = 73 [37.1%]), and popliteal veins (n = 76 [38.6%]), with the most common reasons for incomplete studies being bandages or fixation devices (46.2%), intolerance of the patient for the study (14.7%), and body habitus or edema (17.4%). Only a minority of incomplete studies not identifying DVT (27.9%) had a follow-up examination performed. The majority of the repeated examinations were performed after incomplete LEVDUS examinations that were originally performed for high-risk screening (80%) as opposed to clinical suspicion for DVT (20%). There was no significant difference in demographic features of patients with initially incomplete studies who did or did not have a follow-up examination and no significant difference in the rates of DVT (13.1%) in complete LEVDUS examinations compared with the rate of DVT found in follow-up examinations of initially incomplete LEVDUS examinations (9.1%; P =.33). Conclusions: The majority of patients with incomplete LEVDUS, even those with symptoms or signs suggestive of DVT, do not have a follow-up examination within 30 days of the incomplete study. The rate of DVT detected in initially complete studies was similar to that in patients with follow-up examinations whose initial study was incomplete and did not identify DVT. This suggests that to avoid missing DVT in patients with incomplete LEVDUS studies, quality assurance programs should be initiated to ensure that follow-up LEVDUS studies are performed after an incomplete LEVDUS examination.