Digital photoplethysmography in the diagnosis of suspected lower limb DVT: is it useful?

to determine the role of digital photoplethysmography (D-PPG) in the diagnosis of deep-vein thrombosis (DVT), in comparison to the "gold standard" of either contrast ascending venography (ACV) or colour-flow duplex imaging (CFDI).

prospective study of 100 hospital inpatients (103 legs) referred to the X-ray department for ACV or CFDI with clinically suspected lower limb DVT in a district general hospital. Each patient was assessed by either ACV or CFDI, and D-PPG.

thirty-seven limbs were found to have DVT as demonstrated by ACV or CFDI. All patients with a venous refilling time (RT) of greater than 20 s and venous pump (VP) of greater than 35 had a normal ACV or CFDI. Using RT of less than 21 s as the optimal cut-off point, D-PPG achieved a sensitivity of 100%, negative-predictive value of 100%, specificity of 47% and positive-predictive value of 51%. By using VP of less than 36 as the optimal cut-off point, a sensitivity of 100%, a negative-predictive value of 100%, a specificity of 35% and positive-predictive value of 46% were achieved.

these results validate the use of portable D-PPG as a useful screening tool for the diagnosis of clinically suspected lower limb DVT. A positive test requires further confirmation by one of the "gold standard" methods, whereas a negative test effectively excludes DVT.