Impedance plethysmography in symptomatic patients in a rehabilitation hospital

Purpose: To determine the utility of impedance plethysmography (IPG) in the diagnosis of deep venous thrombosis (DVT) in symptomatic patients in a rehabilitation hospital. Methods: Retrospective review for a 1 year period (1997) of all IPG performed for suspected DVT in symptomatic patients in a rehabilitation hospital. Abnormal IPG was confirmed by compression ultrasound (US). Patients with normal IPG were followed by repeat IPG, US, or clinical progression of symptoms. Mean clinical follow up was 6 weeks. Results: 43 patients were identified. There were 16 abnormal and 27 normal initial IPG. 5 of the 16 abnormal IPG were confirmed by US. Of the 27 normal baseline IPG only one developed a DVT on follow up. This 1 DVT was found by repeat abnormal IPG and confirmed by US. The sensitivity of IPG for DVT was 83% and the specificity was 70%. The negative predictive value was 96% and the positive predictive value was 31%. Conclusions: A normal IPG in a symptomatic patient in a rehabilitation hospital setting makes the development of a clinically significant venous thromboembolism highly unlikely. However an abnormal IPG has a high likelihood of being falsely positive and needs confirmation. Clinical Implications: Since it may be difficult to transport these patients for US, IPG, which is inexpensive, performed at the bedside and easily interpreted, is useful in the evaluation of a suspected DVT in a free standing rehabilitation facility. As shown in other patient populations, it is safe to withhold anticoagulation in rehabilitation patients with clinically suspected DVT, if their initial IPG is normal provided follow up is available.