title: External validity of a randomised clinical trial of temporomandibular disorders: analysis of the patients who refused to participate in research.
abstract: OBJECTIVE
  To assess the external validity of a randomised clinical trial (RCT) of a painful condition.
  
  
  METHODS
  Consecutive patients with painful temporomandibular disorders (TMDs) were invited to participate in a clinical trial. Patients who refused to participate were compared to those who agreed to participate in this study with respect to degree of symptoms at time of presentation.
  
  
  RESULTS
  The patients who refused to participate had more pain, and their condition interfered more with their daily life than those who accepted the invitation to participate.
  
  
  CONCLUSIONS
  Selection bias in RCTs of painful conditions can skew the results, and external validity should be analysed before the results are generalised.
authors.affiliation: The Second Department of Oral and Maxillofacial Surgery, School of Dentistry, Aichi-Gakuin University, Japan. MXE05064@nifty.ne.jp
authors.forename: H
authors.initials: H
authors.lastname: Yuasa
authors.forename: K
authors.initials: K
authors.lastname: Kurita
authors.forename: P-L
authors.initials: PL
authors.lastname: Westesson
mesh_terms: D000203:Activities of Daily Living; D000293:Adolescent; D000328:Adult; D000368:Aged; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000627:therapeutic use; D005081:Exercise Therapy; D005500:Follow-Up Studies; D006801:Humans; D008875:Middle Aged; D010147:Pain Measurement; D016032:Randomized Controlled Trials as Topic / Q000706:statistics & numerical data*; D016059:Range of Motion, Articular / Q000502:physiology; D015983:Selection Bias; D018709:Statistics, Nonparametric; D013705:Temporomandibular Joint Disorders / Q000503:physiopathology / Q000628:therapy*; D016312:Treatment Refusal / Q000706:statistics & numerical data*
chemical_list: D000894:Anti-Inflammatory Agents, Non-Steroidal