Direct comparison of the international hip outcome tool (iHOT-33) and its short version (iHOT-12) in patients with symptomatic hip disorders: A structural and construct validity and reliability study

Background Previous research has shown that the International Hip Outcome Tool (iHOT-33) and its short version (iHOT-12) have shown sufficient psychometric properties, but evidence as to which instrument has the best measurement properties is lacking.Objective To perform a simultaneous comparison of the psychometric properties of the iHOT-33 and iHOT-12 in patients with symptomatic hip and groin disorders.Methods After translation and cross-culturally adaptation into the Italian language, iHOT-33 and iHOT-12, along with other different instruments, were administered to 117 adults with musculoskeletal hip pain. Feasibility (floor/ceiling effect), structural validity (confirmatory factor analysis [CFA]), internal consistency (Cronbach’s alpha [α]), test-retest reliability (intraclass correlation coefficient [ICC3,1]), measurement error (Minimal Detectable Change [MDC95]) and construct validity (hypothesis testing) were assessed.Results Feasibility was supported (no floor/ceiling effect). CFAs showed a one-factor structure for iHOT-33 (comparative fit index [CFI]=0.989; Tucker-Lewis index [TLI]=0.983; root means square residual [RMSEA]=0.034; standardized root mean square residual [SRMR]=0.054) and iHOT-12 (CFI = 0.989; TLI = 0.985; RMSEA = 0.042; SRMR = 0.045). Internal consistency was acceptable for iHOT-33 (α = 0.975) and iHOT-12 (α = 0.922). Test-retest reliability was good for iHOT-33 (ICC = 0.806) and iHOT-12 (ICC = 0.830). Measurement errorswere quite high (MDC95 = 24.8and 22.8 points for iHOT-33 and iHOT-12, respectively). Construct validity was satisfactory for each instrument (100%a-priori hypotheses met).Conclusion iHOT-33 and iHOT-12 were found to be reliable and valid. However, the measurement error could be high for both instruments; however iHOT-12 presented a lower measurement error. Therefore, iHOT-12 should be preferred if compared to iHOT-33 fordisability assessment in patients with symptomatic hip and groin disorders.