title: Cardiovascular outcome ascertainment was similar using blinded and unblinded adjudicators in a national prospective study.
abstract: OBJECTIVE
  Observational studies can avoid biases by blinding medical records to characteristics of interest before outcome adjudication. However, blinding is costly. We assessed the effect of blinding race and geography on outcome ascertainment.
  
  
  METHODS
  The Reasons for Geographic and Racial Differences in Stroke - Myocardial Infarction (REGARDS-MI) Study is an ancillary study to the REGARDS national prospective cohort study including 30,228 participants. The primary characteristics of interest are race and geography, and the prespecified acceptable agreement rate between adjudicators is set at less than 80%. We selected 116 suspected cardiovascular events that underwent adjudication with usual blinding. At least 3 months later, cases were readjudicated without blinding race and geographic location of the patient. We assessed differences in outcome ascertainment using Cohen's kappa statistic and ARs.
  
  
  RESULTS
  Agreement between blinded and unblinded reviews was good to excellent for all four outcomes. kappa statistics were 0.80 (chest pain), 0.85 (heart failure), 0.86 (revascularization), and 0.74 (MI) (P<0.0001 for all). Within each outcome, ARs were similar for race and geographic groups (agreement: 83-100%).
  
  
  CONCLUSIONS
  In observational studies, blinding medical record review for outcome ascertainment for some types of patient characteristics may cause an unwarranted expense.
authors.affiliation: Division of Preventive Medicine, Department of Medicine, University of Alabama at Birmingham, AL, USA. gparmar@dopm.uab.edu
authors.forename: Gaurav
authors.initials: G
authors.lastname: Parmar
authors.forename: Pallavi
authors.initials: P
authors.lastname: Ghuge
authors.forename: Jewell H
authors.initials: JH
authors.lastname: Halanych
authors.forename: Ellen
authors.initials: E
authors.lastname: Funkhouser
authors.forename: Monika M
authors.initials: MM
authors.lastname: Safford
mesh_terms: D015982:Bias; D044383:Black People; D002637:Chest Pain / Q000208:ethnology / Q000628:therapy*; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D008297:Male; D008499:Medical Records; D009203:Myocardial Infarction / Q000208:ethnology / Q000628:therapy*; D011446:Prospective Studies; D016896:Treatment Outcome; D014481:United States; D044465:White People; D001741:Black or African American