The Ability of Non-invasive Physiological Tests to Detect Arterial Occlusions in the Lower Extremity

An ROC study with particular regard to recruitment of patients for clinical trials

Abstract

In the prerandomization phase of a clinical trial it is essential to be able to exclude, in a non-invasive way, patients who cannot be randomized into the trial. The ability of routine non-invasive physiological examinations to detect arterial occlusion in the lower extremities was investigated in 182 patients with hypercholesterolaemia. Ankle blood pressure measurement, pulse oscillometry, digital pulse plethysmography and treadmill and cycle exercise tests were performed as part of the prerandomization phase of the Probucol Quantitative Regression Swedish Trial (PQRST). The PQRST was designed to compare the antiatherosclerotic effect of two different lipid-lowering regimens. Before randomization the patients also underwent aorto-femoral arteriography, which was used as ‘gold standard’. The results were analysed with ROC methodology. Ankle blood pressure measurement (ABP) and inclination time (IT), measured with digital pulse plethysmography, without significant mutual difference, were the variables, best able to detect occlusions. For ABP, the A_Z -values were 0.85, 0.82 and 0.94 in detection of right-sided, left-sided and bilateral occlusion, respectively. The corresponding figures for IT were A_Z = 0.86, 0.91 and 0.93. If a bilateral occlusion was predicted in a patient with an ABP value of ≤ 0.98, a specificity of 0.90 and a sensitivity of 0.87 were obtained, using arteriography as reference method. For IT, with a critical value of 320 ms, sensitivity and specificity were 0.83 and 0.90, respectively.