Can Increased Incidence of Deep Vein Thrombosis (DVT) be Used as a Marker of Quality of Care in the Absence of Standardized Screening? The Potential Effect of Surveillance Bias on Reported DVT Rates after Trauma Elliott R. Haut, MD, Kathy Noll, MSN, David T. Efron, MD, Sean M. Berenholz, MD, Adil Haider, MD, MPH, Edward E. Cornwell III, MD, and Peter J. Pronovost, MD, PhD Background: Deep vein thrombosis (DVT) is a significant cause of morbidity and mortality in trauma patients, even with appropriate prophylaxis. Many na- tional agencies (Agency for Healthcare Research and Quality, Joint Commis- sion, National Quality Forum) have sug- gested DVT incidence as a measurement of health care quality, but none has recom- mended a standardized screening approach. Duplex ultrasound serves an important role as a noninvasive diagnostic tool for detection of DVT. However, screening of asymptomatic patients for DVT is some- what controversial and these practices vary widely among trauma centers. We hy- pothesized that as the number of screening duplex examinations in trauma patients in- creases, the rate of DVT identification will also increase. Methods: Retrospective cohort study of 21,961 patients from an urban, univer- sity-based Level I trauma center for more than 11 years (1995–2005). We grouped patients according to admission at the trauma service either before or after im- plementation of a written practice manage- ment guideline for DVT prophylaxis and duplex ultrasound surveillance in 1998. We compared duplex, DVT, and pulmo- nary embolism rates per 1,000 trauma ad- missions using Fisher’s exact test. Results: The proportion of trauma pa- tients having a duplex ultrasound increased significantly (20.9 – 81.5 per 1,000 trauma admissions, p < 0.0001). The rate of DVT reported increased 10-fold (0.7–7.0 per 1,000 admissions, p  0.0024), significantly, between the two periods. The pulmonary embolism rate increased almost fivefold (0.7–3.2 per 1,000 admissions, p  0.15), although this difference was not statistically significant. Conclusions: Increasing the number of duplex screening exams resulted in an increased rate of DVT identification. In the absence of standardized surveillance, DVT rates may be more influenced by how often caregivers look for these events rather than the quality of care provided. Key Words: Deep vein thrombosis, Duplex surveillance, Quality of care, Screening, Trauma, Pay for performance, Surveillance bias. J Trauma. 2007;63:1132–1137. D eep vein thrombosis (DVT) is a common occurrence and causes significant morbidity and mortality after major trauma. The reported rate of DVT varies widely depending upon many factors. The rate of DVT is related to injury severity and patient-specific variables. 1 It may be as high as 58% 2 or as low as 0.36% 1 in trauma patients depend- ing upon how diligent clinicians are at looking for these often clinically silent DVTs. Many trauma centers have implemented guidelines for DVT prophylaxis in an attempt to decrease morbidity and mortality associated with the development of potentially le- thal pulmonary emboli (PE). Guidelines often utilize risk stratification to target those at highest risk for developing PE for the most aggressive prophylaxis. However, even when providers are diligent with prophylaxis regimens, trauma pa- tients are still at risk for developing DVT and PE. Duplex ultrasound is commonly used to detect DVT. The Eastern Association for the Surgery of Trauma guidelines sug- gest that “duplex ultrasound may be used to assess symptomatic trauma patients with suspected DVT without confirmatory venography” based upon Level I evidence. 3 However, the data for screening of asymptomatic patients for DVT is somewhat conflicting and these practices vary widely among trauma cen- ters. Some authors have suggested that routine duplex screening for DVT in asymptomatic high-risk trauma patients may have some utility. 4–8 The goal of DVT detection in asymptomatic patients is to allow treatment of the DVT to prevent propagation or embolization of the clot and death from PE. Cippolle et al. stressed that adherence to a prophylaxis protocol is more impor- tant than screening duplex at preventing thromboembolic complications. 9 Others emphasize that the large expenditure to screen asymptomatic patients may be cost prohibitive. 10 –13 Submitted for publication December 14, 2006. Accepted for publication June 25, 2007. Copyright © 2007 by Lippincott Williams & Wilkins From the Division of Trauma and Surgical Critical Care, Department of Surgery (E.R.H., K.N., D.T.E., S.M.B., A.H., E.E.C., P.J.P.); Department of Anesthesiology and Critical Care Medicine (E.R.H., D.T.E., S.M.B., E.E.C., P.J.P.), The Johns Hopkins University School of Medicine; and Department of Health Policy and Management (E.E.C., P.J.P.), Johns Hopkins University Bloomberg School of Public Health, Baltimore, Maryland. Presented at the 20th Annual Meeting of the Eastern Association for the Surgery of Trauma, January 16 –20, 2007, Fort Myers, Florida. Address for reprints: Elliott R. Haut, MD, FACS, Department of Surgery, The Johns Hopkins Hospital, 600 N. Wolfe St., 625 Osler, Balti- more, MD 21287; email: ehaut1@jhmi.edu. DOI: 10.1097/TA.0b013e31814856ad The Journal of TRAUMA  Injury, Infection, and Critical Care 1132 November 2007