title: Reproducibility of peripheral arterial tonometry measurements in male cardiovascular patients.
abstract: BACKGROUND
  Assessment of endothelial function of the microvasculature by peripheral arterial tonometry (EndoPAT(®)) 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(®) parameters in patients with stable CAD.
  
  
  METHODS
  EndoPAT(®) measurements were performed repeatedly in 78 male patients (age 66 ± 8 years) 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 90-150 s as used for calculation of the RHI (PAT ratio90-150 s) and 90-120 s (PAT ratio90-120 s) as used for the often employed Framingham RHI (F-RHI), as well as PAT ratio of the peak hyperemic response (PAT ratiopeak response). Additionally, least significant changes (LSC) for individual subjects and minimum sample sizes for parallel and cross-over design studies were calculated.
  
  
  RESULTS
  Mean RHI was 1·84 (SD 0·36). For RHI, PAT ratio90-150 s , PAT ratio90-120 s , and PAT ratiopeak response the CVs were 17·0%, 25·4%, 26·1%, and 25·0%, respectively. The ICCs were 0·45, 0·49, 0·48 and 0·51, respectively, and LSC for RHI was 47·2%.
  
  
  CONCLUSIONS
  CV 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.
authors.affiliation: Preventive Cardiology & Sports Medicine, University Clinic for Cardiology, Inselspital, University Hospital, Bern, Switzerland; Exercise Physiology, Institute for Human Movement Sciences, ETH Zurich, Zurich, Switzerland.
authors.forename: Markus
authors.initials: M
authors.lastname: Nil
authors.forename: Daniela
authors.initials: D
authors.lastname: Schäfer
authors.forename: Thomas
authors.initials: T
authors.lastname: Radtke
authors.forename: Hugo
authors.initials: H
authors.lastname: Saner
authors.forename: Matthias
authors.initials: M
authors.lastname: Wilhelm
authors.forename: Prisca
authors.initials: P
authors.lastname: Eser
mesh_terms: D000368:Aged; D003324:Coronary Artery Disease / Q000503:physiopathology*; D003430:Cross-Sectional Studies; D004730:Endothelium, Vascular / Q000502:physiology*; D006801:Humans; D006940:Hyperemia / Q000503:physiopathology; D008297:Male; D008365:Manometry / Q000379:methods; D055806:Microvessels / Q000502:physiology; D015203:Reproducibility of Results
keywords: Endothelial function; peripheral arterial tonometry; precision; reactive hyperemic index; reproducibility