Appropriate use of D-dimer testing can minimize over-utilization of venous duplex ultrasound in a contemporary high-volume hospital

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BACKGROUND—The sensitivity of D-dimer (DD) in detecting deep venous thrombosis (DVT) is remarkably high, however many institutions send patients immediately for a venous duplex ultrasound (VDU). This study was designed to examine the appropriate utilization of DD and VDU in a high volume hospital. METHODS—A retrospective study was conducted on consecutive patients who presented to a high volume emergency department (ED) with lower extremity limb swelling/pain over a 30-day period, who were sent for VDU during an evaluation for DVT. VDU data were merged with electronic DD lab results. The enzyme-linked immunosorbent assay (ELISA) method was used to provide DD values and thresholds. Values above 0.60 mg/SEU were considered abnormal. RESULTS—We reviewed the medical records of 517 ED patients in the month of June, 2013. After applying the Wells criteria, 157 patients (30.4%) were excluded due to a history of DVT or PE, having been screened for shortness of breath, or sent for surveillance; leaving 360 for analysis. The average age was 59.3±16.5 years with more females (210, 58.3%), and the majority reported limb pain or swelling (73.9%). DD was performed on 51 patients with an average value of 3.6±5.4 mg/SEU, of which 43 (84.3%) were positive. DD identified all positive and negative DVT patients (100% sensitivity and negative predictive value), but also included 40 false positives (16.7% specificity). On the other hand, 309 patients were sent directly to VDU without DD; of those, 43 (13.9%) were positive for DVT. However, 266 (86.1%) patients were negative for DVT by VDU without DD, and these were deemed improper by our current study protocol. Potential charge savings were calculated as VDU for all (360 × $1000 = $360,000), DD for all (360 × $145= $52,200), and VDU for both true and false positives (estimated to be about 25% of the cases; 90 × $1000 = $90,000); this equals a charge savings of $217,800 and would avoid unnecessary VDUs. CONCLUSIONS—Based on the results of our study, we suggest that the DD test be utilized during the initial workup for patients with limb swelling/pain in the emergency room. Appropriate utilization of DD, as well as other clinical criteria, may limit the over-utilization and added cost of VDU, without a negative impact on patient care. The results of DD tests should be utilized to limit the number of patients sent for VDU to only those patients with a positive DD or other significant underlying concerns.