Sensitivity and Specificity of Pulse Oximetry and Ankle-Brachial Index for Screening Asymptomatic Peripheral Vascular Diseases in Type 2 Diabetes Mellitus.

OBJECTIVES To compare pulse oximetry and Ankle-Brachial Index (ABI) with duplex ultrasonography as reference standard to determine the diagnostic accuracy for screening asymptomatic PVD in type 2 diabetes mellitus. METHODS This cross-sectional study was conducted in 2012 at tertiary hospital in Madurai among diabetic patients attending the medicine outpatient department (OPD). Type 2 Diabetes Mellitus patients, asymptomatic with regards to symptoms and signs of PVD, aged above 40 years were included. Pulse Oximetry was performed using a pulse oximeter and ABI using sphygmomanometer cuffs and duplex ultrasonography of femoral, popliteal, tibial, posterior tibial and dorsalis pedis arteries. A diagnosis of PVD was based on: monophasic waveforms in any artery by duplex ultrasonography, toe saturation being less than finger saturation by >2% or if foot saturation decreased by >2% in an elevated position and an ABI <0.9. RESULTS Among 120 patients included in the study, prevalence of PVD was 22.5% (95% CI: 15.9, 30.8). The PVD group had a higher proportion of elderly, males, current smokers, long-standing diabetics and comorbidities. The sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of pulse oximetry were 74.1% (95% CI: 55.3, 86.8), 95.7% (89.4, 98.3), 83.3% (64.1, 93.3) and 92.7% (85.7, 96.4) respectively, while those of ABI were 70.3% (51.5, 84.2), 87.1 (78.8, 92.5), 61.3% (43.8, 76.3) and 91.0% (83.3, 95.4) respectively. Parallel testing had net sensitivity increased to 92.3% and net specificity decreased to 83.3%. Performances did not differ across the subgroups. CONCLUSIONS Pulse oximetry was atleast as good as ABI for the screening for asymptomatic PVD among diabetics.