Lessons from the Post Coronary Artery Bypass Graft study in evaluating andcontrolling technical variability in angiographic trials

Although many investigators have evaluated the technical variability of qua ntitative angiographic techniques used to study atherosclerosis regression in native coronary arteries, few have studied the variability inherent in r epeated studies of atherosclerotic saphenous vein grafts. This study descri bes 2 studies performed during the course of the Post Coronary Artery Bypas s Graft (CABG) Clinical Trial that were designed to assess the reproducibil ity of: (1) repeated angiographic views within a short time period; and (2) reproducibility of the total process of quantitative analysis of saphenous vein graft angiograms. Statistical methods are described that provide a mo re meaningful assessment of the impact of measurement variability in the an alytic process versus the variability related to changes induced by pharmac ologic interventions. One such method, the increase in standard deviation ( SD) among patients (ISDP), showed that repeated angiographic views increase d the variability of calculation of lesion minimal diameter by 1.5%, wherea s the ISDP for repetition of the entire process of quantitative angiographi c readings increased variability 6.4%. These data from the post CABG trial reveal that technical variability is small and has negligible impact on the conclusions of the study. (C) 2001 by Excerpta Medica, Inc.