Test-retest reliability and smallest detectable change of the Bristol Impact of Hypermobility (BIoH) questionnaire. 
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).  A test-retest reliability study.  Participants were recruited from the Hypermobility Syndromes Association, a patient organisation in the United Kingdom.  Recruitment packs were sent to 1080 adults who had given permission to be contacted about research.  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).  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).  The results provide further evidence of the potential of the BIoH questionnaire to underpin research and clinical practice for people with JHS.