Comparism of Pulse Oximetry and Ankle Brachial Index in Screening for Ischemia in Diabetic Foot Ulcers

Abstract

Introduction: Peripheral arterial disease is implicated in the pathogenesis of foot ulcers amongst diabetics, and also has a strong predictive value for cardiovascular mortality. Ankle brachial index (ABI), which is the commonest and standard clinical screening tool requires elaborate training, is time consuming, and difficult to do in a busy clinic. Aims: This study aimed to assess the sensitivity of pulse oximetry (SpO2) in diagnosing peripheral arterial disease (PAD) among adult diabetic patients presenting with foot ulcers, and to compare its diagnostic performance, including sensitivity, specificity, and accuracy, with that of ABI. Materials and Methods: Adult diabetic patients aged 18–70 years presenting with foot ulcers at two tertiary hospitals in South Eastern Nigeria were prospectively enrolled over one year. ABI and peripheral oxygen saturation (SpO2) were measured in both the ulcerated and contralateral limbs. Measurements from the affected and unaffected limbs were compared for both ABI and SpO2 values. Sensitivity, specificity, and overall diagnostic accuracy of pulse oximetry relative to ABI as the reference standard were calculated. Results: Seventy subjects participated in the study, with a male to female sex ratio of 1.12:1. Mean age of participants was 57.69 years, and mean Diabetes mellitus duration was 9.80 years. Mean foot ulcer duration was 13.17 weeks. Subjects mean ABI for diseased leg was 1.02, and 1.00 for normal leg. We found 32.8% of subjects had PAD diagnosed by ABI, and 20.3% diagnosed using pulse oximeter. Pulse oximeter had a sensitivity and specificity of 23.81% and 83.70%, respectively, with an overall diagnostic accuracy of 65.71%. Conclusion: This study showed that ABI has a higher sensitivity in comparison with pulse oximeter in detecting ischemia among diabetics with foot ulcers. Pulse oximetry should not replace ABI as a standalone screening tool in detecting ischemia among diabetics with foot ulcer due to its low sensitivity of 23.8%.