Reproducibility of peripheral arterial tonometry measurements in male cardiovascular patients

BackgroundAssessment of endothelial function of the microvasculature by peripheral arterial tonometry (EndoPAT((R))) has gained increasing popularity in patients with cardiovascular risk factors. Only limited knowledge about its reproducibility in patients with coronary artery disease (CAD) is available. We therefore aimed to quantify reproducibility of EndoPAT((R)) parameters in patients with stable CAD. DesignEndoPAT((R)) measurements were performed repeatedly in 78 male patients (age 668years) with CAD on stable medication. We calculated overall mean, standard deviation (SD), coefficient of variation (CV) and intraclass correlation coefficient (ICC) of the following parameters: reactive hyperemic index (RHI), PAT ratio of the postocclusion period 90-150s as used for calculation of the RHI (PAT ratio(90-150s)) and 90-120s (PAT ratio(90-120s)) as used for the often employed Framingham RHI (F-RHI), as well as PAT ratio of the peak hyperemic response (PAT ratio(peak response)). Additionally, least significant changes (LSC) for individual subjects and minimum sample sizes for parallel and cross-over design studies were calculated. ResultsMean RHI was 184 (SD 036). For RHI, PAT ratio(90-150s), PAT ratio(90-120s), and PAT ratio(peak response) the CVs were 170%, 254%, 261%, and 250%, respectively. The ICCs were 045, 049, 048 and 051, respectively, and LSC for RHI was 472%. ConclusionsCV of RHI in our population was moderate; however, we consider this precision insufficient to monitor changes in individual patients, as they would need to exceed 47% to show a significant change. Further, the poor ICCs reflect the difficulty of detecting treatment effects in homogenous populations, such as patients with stable CAD.