title: Factors associated with incomplete DASH questionnaires.
abstract: BACKGROUND
  Missing data are unavoidable in clinical research. Older age, female gender, and fewer years of education are risk factors for missing items in a questionnaire. This study assessed the differences between patients with complete and incomplete Disabilities of the Arms, Shoulder and Hand (DASH) questionnaires in terms of demographics and psychological factors.
  
  
  METHODS
  We analyzed a convenience sample of 1,204 patients enrolled in eight prospective studies. The DASH and the Pain Catastrophizing Scale were completed by all patients. The Center for Epidemiologic Studies Depression scale, Patient Health Questionnaire, Pain Anxiety Symptoms Scale, and an ordinal pain scale were completed by 745, 493, 545, and 391 patients, respectively. Bivariate analysis and binary logistic regression were used to determine risk factors for incomplete (one or more unanswered question) or invalid (more than three unanswered questions) DASH questionnaires.
  
  
  RESULTS
  Thirty-one percent of patients did not complete all questions on the DASH. Patients with an incomplete DASH were older, had fewer years of education, and had higher levels of catastrophic thinking, depression, and pain anxiety. Age and catastrophic thinking were retained in the best logistic regression models of predictors of both incomplete and invalid DASH questionnaires.
  
  
  CONCLUSIONS
  The observation that patients who complete disability questionnaires are different from patients who do not may affect the interpretation of clinical research. Computer adaptive testing may be preferable to avoid incomplete questionnaires.
  
  
  METHODS
  Prognostic Level II.
authors.affiliation: Orthopaedic Hand and Upper Extremity Service, Massachusetts General Hospital, Boston, MA USA.
authors.forename: Arjan G J
authors.initials: AG
authors.lastname: Bot
authors.affiliation: Orthopaedic Hand and Upper Extremity Service, Massachusetts General Hospital, Boston, MA USA.
authors.forename: Steven
authors.initials: S
authors.lastname: Ferree
authors.affiliation: Orthopaedic Hand and Upper Extremity Service, Massachusetts General Hospital, Boston, MA USA.
authors.forename: Valentin
authors.initials: V
authors.lastname: Neuhaus
authors.affiliation: Harvard Medical School, Orthopaedic Hand and Upper Extremity Service, Massachusetts General Hospital, Yawkey Center, Suite 2100, 55 Fruit Street, Boston, MA 02114 USA.
authors.forename: David
authors.initials: D
authors.lastname: Ring
keywords: Disability; Incomplete questionnaires; Research