Detection of previous proximal venous thrombosis with Doppler ultrasonography and photoplethysmography
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To evaluate the reliability of two noninvasive tests, the photoplethysmograph (PPG) and venous Doppler ultrasound, in determining the presence or absence of previous proximal deep vein thrombosis (DVT), we performed a blinded retrospective cohort study of patients with objectively confirmed (DVT+) or refuted (DVT-) previous episodes of suspected DVT. Twenty-nine of 33 DVT+ patients had abnormal PPG and/or reflux by venous Doppler ultrasound, whereas 39 of 49 DVT- patients had normal PPG and no Doppler reflux (sensitivity, 88%; specificity, 80%). Of 33 DVT+ patients, 20 had abnormal Doppler results (sensitivity, 61%), in contrast to 46 of 49 DVT- patients with normal results (specificity, 94%). Moreover, 23 of 33 DVT+ patients showed abnormal PPG results (sensitivity, 70%), whereas 40 of 49 DVT- patients had normal PPG (specificity, 82%). Based on our findings, the presence of Doppler reflux is specific for previous proximal DVT, whereas a combination of normal PPG and Doppler ultrasound is reliable for excluding previous proximal DVT. Abnormal PPG with normal Doppler ultrasound does not reliably predict the presence or absence of previous DVT. However, this occurred in only 16 of 82 patients. Therefore, the combination of PPG and venous Doppler ultrasound can reliably predict the presence or absence of previous proximal DVT in most patients.