Diagnostic Potential of Combined Photoplethysmography and Ankle-Brachial Index in Peripheral Arterial Disease: A Duplex Ultrasonography-Based Comparative Study.

Background: Although ankle-brachial index (ABI) and photoplethysmography (PPG) have also shown adequate sensitivity in detecting peripheral arterial disease, their diagnostic performance is less reliable in asymptomatic cases or those with high atherosclerotic cardiovascular risks.
Methods and Results: We evaluated 130 participants using ABI, PPG, and duplex ultrasonography, diagnosing 65 with peripheral arterial disease. From the PPG, we derived 2 parameters: PPG amplitude ratio of the lower-to-upper extremities (PPG _ratio ) and the PPG amplitude of the lower extremity (PPG _amp ). Sensitivity, specificity, accuracy, and the area under receiver operating characteristic (ROC) curve were calculated for PPG parameters and ABI, and their combination of both methods. Univariate and multivariate logistic regression assessed the prognostic potential of these parameters. ROC analysis revealed optimal cutoff values in diagnosing peripheral arterial disease were 0.417 for PPG _ratio and "58" for PPG _amp . Both PPG _ratio and PPG _amp demonstrated significantly higher sensitivities, 78.4% and 75.7%, respectively, compared with 55.9% for ABI <0.9 ( P <0.05). The areas under the ROC curves of combination models, including model 1 (ABI <0.9 and PPG _ratio ), model 2 (ABI <0.9 and PPG _amp ), and model 3 (ABI <0.9, PPG _ratio , and PPG _amp ), exhibited improved performance with areas under the ROC curves of 0.922, 0.922, and 0.931 (all P <0.01) compared with ABI alone (area under the ROC curve, 0.822). Additionally, the PPG parameters, both alone and combined with ABI, were associated with major adverse cardiac events and all-cause mortality after adjusting for other relevant factors.
Conclusions: On the basis of duplex ultrasonography, combining ABI and PPG markedly improves peripheral arterial disease diagnosis in high-risk individuals compared with either method alone and provides crucial insights into major adverse cardiac events and all-cause mortality risks.