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Clinical Decisionmaking

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Use of a clinical decision rule can improve the accuracy and efficiency of orthopedists in diagnosing deep vein thrombosis

Patients who undergo orthopedic surgery or suffer orthopedic injuries are at substantial risk for developing proximal deep vein thrombosis (PDVT). This blood clot in the popliteal vein of the knee and above is important to diagnose because it can become life-threatening if it travels to the lungs. Orthopedists could improve their diagnosis of PDVT by using a clinical decision rule, according to two recent studies. The studies were supported in part by the Agency for Healthcare Research and Quality (HS13059) and led by Daniel L. Riddle, Ph.D., P.T., of Virginia Commonwealth University.

In the first study, Dr. Riddle and his colleagues assessed whether a set of clinical characteristics, a so-called clinical decision rule, was valid for diagnosing or ruling out PDVT in outpatients with musculoskeletal disorders. A score of 3 or more on a list of clinical findings (for example, entire leg swelling, calf swelling of at least 3 cm more than the asymptomatic leg, paralysis or immobilization of the lower extremities, recently bedridden for more than 3 days, or major surgery within 4 weeks) equaled a high probability of PDVT. A score of 1 or 2 indicated a moderate probability of PDVT, and 0 equaled a low probability of PDVT.

The researchers used data collected from 464 outpatients with surgical and nonsurgical musculoskeletal disorders and found that 5.6 percent of patients in the low probability group had PDVT compared with 14.1 percent in the moderate probability group and 47.4 percent in the high probability group.

In the second study, Dr. Riddle and his colleagues surveyed a nationally representative random sample of 676 orthopedists. The orthopedists were asked to estimate the probability of PDVT among six hypothetical clinical vignettes using defined criteria. For the moderate and high risk vignettes, orthopedists' planned diagnostic tests agreed with the gold standard (clinical decision rule and evidence-based diagnostic test recommendations) about 70 percent of the time. The researchers conclude that orthopedists could probably improve their diagnosis of PDVT by applying the clinical decision rule and current evidence on use of diagnostic tests.

More details are in "Preliminary validation of clinical assessment for deep vein thrombosis in orthopaedic outpatients," by Dr. Riddle, Marnix R. Hoppener, M.Sc., Roderik A. Kraaijenhagen, M.D. and others; and "Improving the diagnostic process for deep vein thrombosis in orthopaedic outpatients," by Dr. Riddle, Bruce E. Hillner, M.D., Philip S. Wells, M.D., and Robert E. Johnson, Ph.D., in the March 2005 Clinical Orthopaedics and Related Research 432, pp. 252-257, 258-266.

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