Purpose: To derive and evaluate a shorter infant/toddler quality of life questionnaire (ITQOL) for use in clinical care.
Methods: Stepwise regression, factor analysis, and item-scaling principles were used to derive and guide item selection using data from a large general sample in the Netherlands (n = 5,211) and a "wheezing illness" sample (n = 138). Item internal consistency, discriminant validity, and floor and ceiling effects were evaluated using a general Dutch sample (Salland Region n = 410) and two clinical samples: Functional abdominal pain (FAP, n = 81) and Burn (n = 194). Reliabilities were estimated using Cronbach's alpha. Relative precision (RP), the ability to distinguish between clinical subgroups, was computed by comparing the proportion of variance explained by the short-form scales versus respective full-length scales.
Results: The ITQOL was reduced from 97 to 47 items. Median alpha coefficients were 0.77 Salland sample, 0.76 (FAP), and 0.84 (Burn). Ninety-one to 100 % scaling successes for item discriminant validity were observed for 21 of 24 tests (8 scales, 3 samples). Floor effects were not observed; some ceiling effects were detected. RP estimates in the Salland sample ranged from 2.40 (physical abilities) to 0.58 (temperament and moods). RP estimates in the FAP sample were 0.85 (bodily pain), 1.36 (temperament and moods) and 1.62 (parental-impact emotional) and for Burn, 1.51 (temperament and moods) and 0.59 (general health perceptions).
Conclusion: The ITQOL-SF47 is reliable and valid and exceeds item-level scaling criteria.