The Diagnostic Potential of Combined Photoplethysmography and Ankle-Brachial Index in Peripheral Arterial Obstructive Disease: A Comparative Analysis with Doppler Ultrasound

Background and aims While ankle-brachial index (ABI) and photoplethysmography (PPG) have also shown adequate sensitivity in detecting PAOD, their accuracies can be compromised in detecting milder cases. We aim to evaluate the diagnostic value of combining ABI and PPG in detecting PAOD for subjects with high atherosclerotic cardiovascular risks compared to duplex sonography. Methods 130 participants underwent ABI, PPG, and duplex sonography during the evaluation process. Two parameters were derived from the PPG-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 operative curve (AUC) were calculated for PPG parameters and ABI, and the combination of both methods. Multivariate analysis was performed for adjusting other relevant risk factors. Results 65 participants were diagnosed with PAOD based on duplex sonography. The ROC analysis revealed optimal cut-off values in diagnosing PAOD 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%, in comparison to 55.9% of ABI<0.9 (p<0.05). Lower PPG ratio and PPG amp remained independently associated with PAOD even after adjusting for confounding factors. The AUC of combination models, including model 1 (ABI and PPG ratio ), model 2 (ABI and PPG amp ), and model 3 (ABI, PPG ratio , and PPG amp ), exhibited improved performance with AUCs of 0.922, 0.922, and 0.931 (all p<0.01) compared to that of ABI alone (AUC:0.822). Conclusions The combination of ABI and PPG increases the sensitivity and accuracy prominently in diagnosing PAOD compared to ABI or PPG alone.