Exercise transcutaneous oxygen pressure measurement has good sensitivity and specificity to detect lower extremity arterial stenosis assessed by computed tomography angiography

Peripheral artery disease (PAD) is a highly prevalent disease diagnosed by the use of ankle-brachial index (ABI) at rest. In some clinical conditions (diabetes, renal insufficiency, advanced age), ABI can be falsely normal and other tests are required for the PAD diagnosis (American Heart Association statement). This study was conducted to determine the accuracy of exercise transcutaneous oxygen pressure measurement (exercise-TcPo2) in detection of arterial stenosis ≥50% using computed tomography angiography (CTA) as the gold standard. We retrospectively analyzed consecutive patients referred to our vascular unit (University Hospital, Rennes, France) for exercise-TcPo2 testing from 2014 to 2015. All included patients had a CTA performed within 3 months of the exercise-TcPo2 test. Exercise-TcPo2 was performed on treadmill (10% slope; 2 mph speed). We calculated the Delta from Resting Oxygen Pressure (DROP) index (expressed in mm Hg) at the proximal and distal levels. Two blinded physicians performed stenosis quantification on CTA. The receiver operating characteristic (ROC) curve was used to define a cutoff point to detect arterial stenosis ≥50%, stenosis ≥60%, and stenosis ≥70%. A total of 34 patients (mean age 64 ± 2 years old; 74% men) were analyzed. The highest areas under the curve (AUC) were found for 60% stenosis at both proximal and distal levels. For stenosis ≥50%, sensitivity and specificity of proximal minimal DROP were 80.9% [67.1–89.7], 81.0% [59.3–92.7] respectively. For stenosis ≥50%, sensitivity and specificity of distal minimal DROP were 73.2% [60.3–83.1], 83.3% [53.8–96.2], respectively. For stenosis ≥60%, sensitivity and specificity of proximal minimal DROP were 82.5% [67.6–91.5] and 85.7% [67.7–94.8] respectively. For stenosis ≥60%, sensitivity and specificity of distal minimal DROP were 80.4% [67.3–89.1] and 88.2% [64.2–97.7], respectively. For stenosis ≥70%, sensitivity and specificity of proximal minimal DROP were 85.7% [67.7–94.8] and 75.0% [59.6–85.9] respectively. For stenosis ≥70%, sensitivity and specificity of distal minimal DROP were 86.0% [72.2–93.7] and 76.0% [56.1–88.7], respectively. Exercise-TcPo2 using a proximal minimal DROP value ≤−15 mm Hg or a distal minimal DROP value ≤−16 mm Hg is accurate to diagnose arterial stenosis especially stenosis ≥60% on the lower limbs. Exercise-TcPo2 is safe and noninvasive test that might be used in second line for PAD diagnosis.