Table 3

Psychometric properties of the classical Health Assessment Questionnaire Disability Index (HAQ-DI) and individualised HAQ scales

HAQ-DIImportance questionnairePreference questionnaire
Individualised HAQ multiplicativeIndividualised HAQ additiveFive-item HAQWeighted five-item HAQ
Mean baseline score*1.40 (0.62)0.92 (055)1.70 (0.46)1.01 (0.64)1.03 (0.66)
Mean change in score†−0.41 (0.55)−0.30 (0.44)−0.19 (0.28)−0.38 (0.59)−0.39 (0.61)
Construct validity: Spearman’s correlation‡ with HAQ-DI score10.880.770.770.76
Internal consistency Cronbach’s α (95% CI)§0.87 (0.85 to 0.89)0.88 (0.85 to 0.90)0.88 (0.86 to 0.90)NENE
Sensitivity to change SRM (95% CI)§0.74 (0.64 to 0.86)0.69 (0.58 to 0.79)0.68 (0.58 to 0.80)0.65 (0.55 to 0.77)0.64 (0.54 to 0.76)
  • Data are presented as mean (SD) unless stated otherwise.

  • *Each score was linearly transformed to a score from 0 to 3. †Mean changes in scores were calculated between the baseline visit at week 0 (W0) and the final visit at week 24 (W24): W24−W0. ‡For Spearman’s correlations, all p values were <0.001; §95% confidence intervals were estimated by the bootstrap method with 1000 replications.

  • HAQ-DI, Health Assessment Questionnaire Disability Index; NE, not estimable; SRM, standardised response mean.