title: Comparison of two methods of estimating reader variability in QT interval measurements in thorough QT/QTc studies.
abstract: BACKGROUND
  Two methods of estimating reader variability (RV) in QT measurements between 12 readers were compared.
  
  
  METHODS
  Using data from 500 electrocardiograms (ECGs) analyzed twice by 12 readers, we bootstrapped 1000 datasets each for both methods. In grouped analysis design (GAD), the same 40 ECGs were read twice by all readers. In pairwise analysis design (PAD), 40 ECGs analyzed by each reader in a clinical trial were reanalyzed by the same reader (intra-RV) and also by another reader (inter-RV); thus, variability between each pair of readers was estimated using different ECGs.
  
  
  RESULTS
  Inter-RV (mean [95% CI]) between pairs of readers by GAD and PAD was 3.9 ms (2.1-5.5 ms) and 4.1 ms (2.6-5.4 ms), respectively, using ANOVA, 0 ms (-0.0 to 0.4 ms), and 0 ms (-0.7 to 0.6 ms), respectively, by actual difference between readers and 7.7 ms (6.2-9.8 ms) and 7.7 ms (6.6-9.1 ms), respectively, by absolute difference between readers. Intra-RV too was comparable.
  
  
  CONCLUSIONS
  RV estimates by the grouped- and pairwise analysis designs are comparable.
authors: Research Section, Quintiles Cardiac Safety Services, Mumbai, India.
authors: Vaibhav
authors: V
authors: Salvi
authors: Dilip R
authors: DR
authors: Karnad
authors: Vaibhav
authors: V
authors: Kerkar
authors: Gopi Krishna
authors: GK
authors: Panicker
authors: Mili
authors: M
authors: Natekar
authors: Snehal
authors: S
authors: Kothari
mesh_terms: D000704:Analysis of Variance; D004562:Electrocardiography / Q000379:methods* / Q000706:statistics & numerical data*; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D015588:Observer Variation; D012107:Research Design
keywords: bootstrapping; data simulation; reader variability; study design; thorough QT study