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 (PPGratio) and the PPG amplitude of the lower extremity (PPGamp). 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 PPGratio and 58 for PPGamp. Both PPGratio and PPGamp demonstrated significantly higher sensitivities, 78.4% and 75.7%, in comparison to 55.9% of ABI<0.9 (p<0.05). Lower PPGratio and PPGamp remained independently associated with PAOD even after adjusting for confounding factors. The AUC of combination models, including model 1 (ABI and PPGratio), model 2 (ABI and PPGamp), and model 3 (ABI, PPGratio, and PPGamp), 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. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement This work was supported by the National Science and Technology Council, Taiwan, under Grant Numbers 111-2221-E-008-103-MY3, awarded to C. Lin, and 112-2218-E-008-015, awarded jointly to M.-T. Lo and C. Lin. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: All the collected data was approved by the institutional review board of the Cathay General Hospital (CGH-P108042) I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes Data will be available upon reasonable request, conditional upon obtaining Institutional Review Board (IRB) approval