Data from: Diagnostic accuracy study of an oscillometric ankle-brachial index in peripheral arterial disease: the influence of oscillometric errors and calcified legs

Background.
Peripheral arterial disease (PAD) is an indicator of widespread atherosclerosis. However, most individuals with PAD, in spite of being at high cardiovascular risk, are asymptomatic. This fact, together with the limitations of the Doppler ankle-brachial index (ABI), contributes to PAD underdiagnose.
The aim of this study was to compare oscillometric ABI and Doppler ABI to diagnose peripheral arterial disease, and also to examine the influence of oscillometric errors and calcified legs on the PAD diagnoses.

Methods and Findings.
We measured the ankle-brachial indexes of 90 volunteers (n = 180 legs, age 70 ± 14 years, 43% diabetics) using both oscillometer OMRON-M3 and Doppler. For concordance analyses we used the Bland and Altman method, and also estimated the intraclass correlation coefficient. Receiver Operating Characteristic Curves were used to examine the diagnostic performance of both methods. The ABI means were 1.06 ± 0.14 and 1.04 ± 0.16 (p = 0.034) measured by oscillometer and Doppler ABIs respectively, with limits of agreement of ± 0.20 and intraclass correlation coefficient = 0.769. Oscillometer yielded 23 "error" measurements, and also overestimated the measurements in low ankle pressures. Using Doppler as gold standard, oscillometer performance for diagnosis of PAD showed an Area Under Curve = 0.944 (sensitivity: 66.7%, specificity: 96.8%). Moreover, when considered calcified legs and oscillometric "error" readings as arteriopathy equivalents, sensitivity rose to 78.2%, maintaining specificity in 96%. The best oscillometer cut-off point was 0.96 (sensitivity: 87%, specificity: 91%, positive likelihood ratio: 9.66 and negative likelihood ratio: 0.14).

Conclusion.
Despite its limitations, oscillometric ABI could be a useful tool for the diagnosis of PAD, particularly when considering calcified legs and oscillometric "errors" readings as peripheral arterial disease equivalents.

背景
外周动脉疾病（Peripheral arterial disease, PAD）是广泛动脉粥样硬化的表征。然而，多数外周动脉疾病患者虽处于心血管疾病高风险状态，却无明显临床症状。这一现状，加之多普勒踝肱指数（Doppler ankle-brachial index, ABI）存在的检测局限，导致外周动脉疾病的诊断不足。
本研究旨在对比示波法踝肱指数与多普勒踝肱指数在诊断外周动脉疾病中的应用效果，同时探讨示波法检测误差与下肢钙化对外周动脉疾病诊断的影响。

研究方法与结果
本研究采用欧姆龙M3型示波仪（OMRON-M3）与多普勒设备，对90名志愿者（共180条下肢，年龄70±14岁，其中糖尿病患者占比43%）的踝肱指数进行检测。一致性分析采用Bland-Altman法，并计算组内相关系数（intraclass correlation coefficient）。通过受试者工作特征曲线（Receiver Operating Characteristic Curves, ROC曲线）评估两种检测方法的诊断效能。
示波法与多普勒法测得的踝肱指数均值分别为1.06±0.14与1.04±0.16（p=0.034），一致性限为±0.20，组内相关系数为0.769。示波法共检出23例“异常”检测结果，且在踝部压力较低时会高估检测值。以多普勒检测结果作为金标准时，示波法诊断外周动脉疾病的曲线下面积为0.944（灵敏度：66.7%，特异度：96.8%）。此外，当将下肢钙化与示波法“异常”读数视为动脉病变等效情况时，灵敏度提升至78.2%，特异度仍维持在96%。示波法的最佳截断值为0.96（灵敏度：87%，特异度：91%，阳性似然比：9.66，阴性似然比：0.14）。

结论
尽管存在一定局限性，示波法踝肱指数仍可作为外周动脉疾病诊断的有效工具，尤其是在将下肢钙化与示波法“异常”读数视为外周动脉疾病等效病变的场景下。