title: Blinding was judged more difficult to achieve and maintain in nonpharmacologic than pharmacologic trials.
abstract: OBJECTIVE
  To compare the feasibility of blinding and the perceived risk of unblinding in trials evaluating pharmacologic (PT) and nonpharmacologic treatments (NPT) of hip or knee osteoarthritis.
  
  
  METHODS
  Two independent reviewers assessed the feasibility of blinding patients, care providers, and outcome assessors, the perceived risk of unblinding, and whether blinding was reported in 110 reports of randomized controlled trials (RCTs) evaluating PT and NPT in patients with hip or knee osteoarthritis.
  
  
  RESULTS
  Blinding was considered to be possible less often in NPT trials than in PT trials for patients (42 vs. 96%; P <.001), care providers (12 vs. 96%; P <.001), and outcome assessors (34 vs. 98%; P <.001). When blinding was judged feasible, the perceived risk of unblinding was more often considered moderate or important in NPT than PT trials for patients (35 vs. 14%, P=.02) and outcome assessors (44 vs. 10%, P=.0004). When blinding was judged feasible, it was reported less often in NPT reports than in PT reports for patients (46 vs. 98%, P <.001), care providers (43 vs. 83%, P=.03), and outcome assessors (72 vs. 98%, P=.0006).
  
  
  CONCLUSIONS
  Blinding appears to be more difficult to achieve and unblinding may occur more often in NPT than PT trials.
authors.affiliation: INSERM EMI 03 57, Département d'Epidémiologie, Biostatistique et Recherche Clinique, Groupe Hospitalier Bichat-Claude Bernard, Assistance Publique-Hôpitaux de Paris, Faculté Xavier Bichat, Université Paris 7, France. isabelle.boutron@bch.ap-hop-paris.fr
authors.forename: Isabelle
authors.initials: I
authors.lastname: Boutron
authors.forename: Florence
authors.initials: F
authors.lastname: Tubach
authors.forename: Bruno
authors.initials: B
authors.lastname: Giraudeau
authors.forename: Philippe
authors.initials: P
authors.lastname: Ravaud
mesh_terms: D004311:Double-Blind Method; D004358:Drug Therapy; D015340:Epidemiologic Research Design; D005240:Feasibility Studies; D006801:Humans; D015207:Osteoarthritis, Hip / Q000628:therapy; D020370:Osteoarthritis, Knee / Q000628:therapy; D016032:Randomized Controlled Trials as Topic; D016037:Single-Blind Method; D016896:Treatment Outcome