Inter-Rater Reliability, Construct Validity, and Feasibility of the Modified “Which Health Approaches and Treatments Are You Using?” (WHAT) Questionnaires for Assessing the Use of Complementary Health Approaches in Pediatric Oncology

Background: This study aimed to test the inter-rater reliability, construct validity, and feasibility of the modified “Which Health Approaches and Treatments Are You Using?” (WHAT) questionnaires in pediatric oncology; Methods: Parent–child dyads were invited to complete self- and proxy-report-modified WHAT, Pediatric Quality of Life Inventory, demographics, a diary of the child’s recent use of CHA, and a questionnaire assessing the aspects of feasibility. Parents were asked to complete a satisfaction of their children’s use of the CHA survey; Results: Twenty-four dyads completed the study. The mean weighted kappa showed strong inter-rater reliability (k = 0.77, SE = 0.056), and strong agreements between the modified WHAT and the diary (self-report [k = 0.806, SE = 0.046] and proxy-report [k = 0.894, SE = 0.057]). Significant relationships were found only between recent and non-recent CHA users in relation to the easy access to CHA (self-report [p = 0.02], proxy-report [p < 0.001]). The mean scores of the feasibility scale (out of 7.0) for the self- and proxy-report were 5.64 (SD = 0.23) and 5.81 (SD = 0.22), respectively, indicating the feasibility of the modified WHAT; Conclusions: The findings provide initial evidence of the reliability and validity of the modified WHAT and their feasibility. Further research is needed to test the theoretical relationships and further explore the validity and reliability of the modified WHAT.