Pulse oximetry as a potential screening tool for lower extremity arterial disease in asymptomatic patients with diabetes mellitus.
BACKGROUND
Lower extremity arterial disease (LEAD) is common and underdiagnosed in patients with diabetes mellitus and is associated with higher total mortality.


METHODS
We compared the accuracy of pulse oximetry, the ankle-brachial index (ABI), and the combination of the two to diagnose LEAD in consecutive outpatients with type 2 diabetes who had no symptoms of LEAD, in a primary care setting. Exclusions were age younger than 40 years, known LEAD, or typical symptoms of LEAD. Fifty-seven patients were enrolled. All patients had (1) ABI measurement; (2) pulse oximetry to measure Sao2 of their index fingers and big toes in the supine position and at 12-in elevation; and (3) Doppler waveform analysis of the lower extremity arteries. The ABI was considered abnormal if it was less than 0.9. Pulse oximetry of the toes was considered abnormal if the Sao2 was more than 2% lower from the finger or on 12-in elevation of the foot. The combination was considered positive if either the ABI or pulse oximetry was positive for LEAD and negative if both were negative. We defined LEAD as monophasic waveforms on waveform analysis.


RESULTS
Of our patients, 31% had LEAD. Pulse oximetry had a sensitivity of 77% (95% confidence interval [CI], 61%-88%) and a specificity of 97% (95% CI, 91%-99%); ABI had a sensitivity of 63% (95% CI, 46%-77%) and a specificity of 97% (95% CI, 91%-99%). Positive likelihood ratios were 30 (95% CI, 7.6-121) for pulse oximetry and 24.8 (95% CI, 6.2-99.8) for ABI; negative likelihood ratios were 0.23 (95% CI, 0.12-0.43) for pulse oximetry and 0.38 (95% CI, 0.25-0.59) for ABI. For the combination, sensitivity was 86% (95% CI, 71%-94%) and specificity was 92% (95% CI, 84%-96%).


CONCLUSIONS
Pulse oximetry of the toes seems as accurate as ABI to screen for LEAD in patients with type 2 diabetes. Combination of the two tests increases sensitivity.
Parameswaran
G Iyer
GI
Department of Medicine, Unity Health System, Rochester, NY 14626, USA. gparameswaran@unityhealth.org
Brand
Kathy
K
Dolan
James
J
D000328:Adult; D000368:Aged; D000842:Ankle / Q000098:blood supply; D001157:Arterial Occlusive Diseases / Q000097:blood / Q000175:diagnosis* / Q000209:etiology; D001794:Blood Pressure / Q000502:physiology; D001916:Brachial Artery / Q000000981:diagnostic imaging / Q000503:physiopathology; D003430:Cross-Sectional Studies; D003924:Diabetes Mellitus, Type 2 / Q000097:blood / Q000150:complications*; D003925:Diabetic Angiopathies / Q000097:blood / Q000150:complications / Q000175:diagnosis; D005260:Female; D005263:Femoral Artery / Q000000981:diagnostic imaging / Q000503:physiopathology; D006801:Humans; D007866:Leg / Q000098:blood supply*; D008297:Male; D008403:Mass Screening / Q000379:methods*; D008875:Middle Aged; D010092:Oximetry / Q000295:instrumentation; D010100:Oxygen / Q000097:blood*; D016491:Peripheral Vascular Diseases / Q000097:blood / Q000175:diagnosis* / Q000209:etiology; D012372:ROC Curve; D015203:Reproducibility of Results; D012189:Retrospective Studies; D018608:Ultrasonography, Doppler
D010100:Oxygen