The construct validity, responsiveness, reliability and interpretability of the Recap of atopic eczema questionnaire (RECAP) in children

Background The Recap of atopic eczema questionnaire (RECAP) was developed to measure eczema control in patients with atopic dermatitis (AD). The measurement properties of RECAP have not yet been validated in caregivers of children with AD. Objectives To assess the construct validity, responsiveness, reliability and interpretability of the Dutch proxy version of RECAP. Methods A prospective validation study was conducted in children (aged < 12 years) with AD and their caregivers (in a Dutch tertiary hospital). At three timepoints (T-0 = baseline; T-1 = after 1-7 days; T-2 = after 4-8 weeks) RECAP and multiple reference instruments were completed by caregivers of child patients. Single- and change-score validity (responsiveness) were tested with a priori hypotheses on correlations with reference instruments. Intraclass correlation coefficients (ICCagreement) and standard error of agreement (SEMagreement) were reported. Bands for perceived eczema control were proposed. The smallest detectable change (SDC) and minimally important change (MIC) were determined. Two anchor-based methods based on receiver operating characteristic curve (ROC) and predictive modelling were used to determine the MIC. Results A total of 231 children with AD and their caregivers participated. Of our a priori hypotheses for single-score and change-score validity, 77% and 80% were confirmed, respectively. A stronger correlation than hypothesized was found for all rejected hypotheses. Excellent reliability was found (ICCagreement = 0.94, 95% confidence interval 0.90-0.96). The SEMagreement was 1.9 points. The final banding was 0-1 (completely controlled), 2-7 (mostly controlled), 8-12 (moderately controlled), 13-18 (a little controlled) and 19-28 (not at all controlled). A cutoff point of >= 8 was selected to identify children whose AD is not under control. The SDC was 5.3 and the MIC values were 1.5 and 3.6 for the ROC and predictive modelling approaches, respectively. No floor or ceiling effects were observed. Results A total of 231 children with AD and their caregivers participated. Of our a priori hypotheses for single-score and change-score validity, 77% and 80% were confirmed, respectively. A stronger correlation than hypothesized was found for all rejected hypotheses. Excellent reliability was found (ICCagreement = 0.94, 95% confidence interval 0.90-0.96). The SEMagreement was 1.9 points. The final banding was 0-1 (completely controlled), 2-7 (mostly controlled), 8-12 (moderately controlled), 13-18 (a little controlled) and 19-28 (not at all controlled). A cutoff point of >= 8 was selected to identify children whose AD is not under control. The SDC was 5.3 and the MIC values were 1.5 and 3.6 for the ROC and predictive modelling approaches, respectively. No floor or ceiling effects were observed. Conclusions The proxy version of RECAP is a valid, reliable and responsive measurement instrument for measuring eczema control in children with AD. An improvement of >= 6 points can be regarded as a real and important change in children with AD.