Test-retest reliability and smallest detectable change of the Bristol Impact of Hypermobility (BIoH) questionnaire

Objective: The Bristol Impact of Hypermobility (BIoH) questionnaire is a patient-reported outcome measure developed in conjunction with adults with Joint Hypermobility Syndrome (JHS). It has demonstrated strong concurrent validity with the Short Form-36 (SF-36) physical component score but other psychometric properties have yet to be established. This study aimed to determine its test-retest reliability and smallest detectable change (SDC). Design: A test-retest reliability study. Setting: Participants were recruited from the Hypermobility Syndromes Association, a patient organisation in the United Kingdom. Patients Recruitment packs were sent to 1080 adults who had given permission to be contacted about research. Main outcome measures BIoH and SF-36 questionnaires were administered at baseline and repeated two weeks later. An 11-point global rating of change scale (−5 to +5) was also administered at two weeks. Test-retest analysis and calculation of the SDC was conducted on ‘stable’ patients (defined as global rating of change −1 to +1). Results: 462 responses were received. 233 patients reported a ‘stable’ condition and were included in analysis (95% women; mean (SD) age 44.5 (13.9) years; BIoH score 223.6 (54.0)). The BIoH questionnaire demonstrated excellent test-retest reliability (ICC 0.923, 95% CI 0.900–0.940). The SDC was 42 points (equivalent to 19% of the mean baseline score). The SF-36 physical and mental component scores demonstrated poorer test-retest reliability and larger SDCs (as a proportion of the mean baseline scores). Conclusion: The results provide further evidence of the potential of the BIoH questionnaire to underpin research and clinical practice for people with JHS.