Utility of ankle brachial index in the diagnosis of peripheral arterial disease in a resource limited setting

Background: Peripheral arterial disease (PAD) constitutes a significant healthcare problem with immense health and economic implications. Owing to ill-equipped healthcare systems in poor countries the diagnosis of PAD demands the availability of a reasonably reliable and inexpensive diagnostic test. Ankle brachial index (ABI) is a simple, inexpensive office-based test for the diagnosis of PAD. The study was aimed to evaluate the reliability of ABI for the diagnosis of PAD using Doppler ultrasound (DUS) as the gold standard. Methods: The ABI of patients suspected of having lower limb PAD was measured followed by DUS examination. The sensitivity and specificity of ABI for the diagnosis of PAD was calculated by comparing it with DUS which was used as the reference or standard diagnostic test. Results: The ABI of a total of 200 limbs from 100 patients was recorded followed by DUS examination. One hundred and thirty-two limbs (66%) had PAD on DUS which was graded as mild, moderate, and severe in 45.5%, 27.2% and 30.3% respectively. Out of 132 patients who had PAD on Doppler, 96/132 (72.8%) were correctly labelled as PAD on ABI, whereas 36/132 (27.2%) received an erroneous diagnosis of normal on ABI. Conversely, only 6/60 (10%) patients who were labelled as PAD on ABI had a normal arterial system on DUS. The ABI yielded a low overall sensitivity of 72.7% and a high specificity of 90%. The sensitivity was relatively low for mild PAD (52.7%), however, for moderate and severe PAD, ABI demonstrated a high sensitivity of 88.9% and 100% respectively. Overall agreement between ABI and DUS for the diagnosis of PAD was good (k = 0.67). Conclusion: ABI demonstrated a good sensitivity and specificity for the diagnosis of PAD especially in patients with moderate-severe PAD. Combined with the advantages of ready availability, low cost, and technical feasibility the use of ABI should be maximized in routine clinical practice to clinch the diagnosis of PAD in suspected individuals.