title: Responsiveness of SF-36 Health Survey and Patient Generated Index in people with chronic knee pain commenced on oral analgesia: analysis of data from a randomised controlled clinical trial.
abstract: (1) To assess the responsiveness of the Short Form 36 Health Survey (SF-36) and Patient Generated Index (PGI) in people with knee pain who were given oral analgesics; and (2) to perform content analysis of the SF-36 and PGI aiming to identify differences between the instruments and causes of different responsiveness.
  
  
  
  An observational study nested within a randomised controlled trial comparing oral paracetamol, ibuprofen or a combination of the two in 884 community-derived people with chronic knee pain. Each participant was given the SF-36 and PGI questionnaires to fill out at baseline, day 10, week 7 and week 13 after commencement on analgesia. Responsiveness was measured as a standardised response mean from baseline, and contents of the instruments were analysed.
  
  
  
  The PGI showed the greater responsiveness to analgesics than the SF-36 throughout the study period. Only the Bodily Pain Score of the SF-36 showed comparable responsiveness to the PGI. The standardised response mean of the PGI at 13 weeks was 0.61 (95% CI 0.51-0.72), and that of the Bodily Pain Score of the SF-36 was 0.49 (95% CI 0.39-0.58). Content analysis of the PGI identified multiple areas which are not represented in the SF-36 which may help explain its performance.
  
  
  
  Overall the PGI is more responsive than the SF-36 to commonly used oral analgesics taken for knee pain. The PGI is able to elicit areas of individualised health-related quality of life which are not captured by the SF-36.
authors.affiliation: Department of Rheumatology, Queen's Medical Centre, Derby Road, Nottingham, NG7 2UH, UK.
authors.forename: Alex
authors.initials: A
authors.lastname: Papou
authors.affiliation: Frimley Park Hospital, Portsmouth Road, Frimley, GU16 7UJ, UK.
authors.forename: Salma
authors.initials: S
authors.lastname: Hussain
authors.affiliation: Division of Rheumatology, Orthopaedics and Dermatology, University of Nottingham, Academic Rheumatology, Clinical Sciences Building, Nottingham City Hospital, Hucknall Road, Nottingham, NG5 1PB, UK.
authors.forename: Daniel
authors.initials: D
authors.lastname: McWilliams
authors.affiliation: Division of Rheumatology, Orthopaedics and Dermatology, University of Nottingham, Academic Rheumatology, Clinical Sciences Building, Nottingham City Hospital, Hucknall Road, Nottingham, NG5 1PB, UK. Weiya.Zhang@nottingham.ac.uk.
authors.forename: Weiya
authors.initials: W
authors.lastname: Zhang
authors.affiliation: Division of Rheumatology, Orthopaedics and Dermatology, University of Nottingham, Academic Rheumatology, Clinical Sciences Building, Nottingham City Hospital, Hucknall Road, Nottingham, NG5 1PB, UK.
authors.forename: Michael
authors.initials: M
authors.lastname: Doherty
mesh_terms: D000082:Acetaminophen / Q000008:administration & dosage / Q000627:therapeutic use*; D018712:Analgesics, Non-Narcotic / Q000008:administration & dosage / Q000627:therapeutic use*; D005260:Female; D006801:Humans; D007052:Ibuprofen / Q000008:administration & dosage / Q000627:therapeutic use*; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000517:prevention & control* / Q000523:psychology; D010146:Pain / Q000517:prevention & control* / Q000523:psychology; D010147:Pain Measurement; D011788:Quality of Life; D015203:Reproducibility of Results; D011795:Surveys and Questionnaires; D016896:Treatment Outcome
chemical_list: D018712:Analgesics, Non-Narcotic; D000082:Acetaminophen; D007052:Ibuprofen
keywords: Health-related quality of life; Knee pain; Osteoarthritis; Patient Generated Index; Responsiveness; SF-36