Development of Functional Abilities Assessment in Paediatric Oncology (FAAP-O) Scale for Children and Adolescents Affected by Cancer

<b>Background/Objectives</b>: Functional abilities are fundamental for social participation. However, functional abilities assessment tools validated for children and adolescents undergoing cancer treatment are lacking. A preliminary validation of the Gross Motor Function Measure-88 (GMFM-88) scale for children with cancer found that some items are unable to discriminate or distinguish between different gross motor function levels. This study aims to develop and validate the Functional Abilities Assessment in Paediatric Oncology (FAAP-O), starting with GMFM-88. <b>Methods</b>: This multicentre study (ClinicalTrials.gov Identifier: NCT04862130) involved children and adolescents (6 months-18 years old) diagnosed with cancer, in any phase of treatment or less than 1 year off therapy. A multiphase mixed-methods design was employed. The content validity of each item of GMFM-88 for the paediatric oncology population was calculated with the Content Validity Ratio (CVR). Items with a CVR score ≥ 0.70 were included in the FAAP-O scale. Other items with a score between 0 and 0.69 were selected for their relevance by consensus with five focus groups and a plenary meeting. The FAAP-O items set was organised in five dimensions by exploratory factor analyses. The calculation of FAAP-O internal consistency was made using Cronbach's α while inter/intra-rater reliability was assessed by intraclass correlation coefficients (ICCs). <b>Results</b>: The study involved 217 subjects. The FAAP-O included 36 items; its internal consistency was good in each dimension (0.90 ≤ α ≤ 0.96) and its inter/intra-rater reliability was excellent (ICC > 0.90). <b>Conclusions</b>: A new specifically validated scale to assess functional abilities in children and adolescents with cancer is provided. Validated tools are necessary for specific, objective rehabilitation assessments, which are fundamental in clinical practice and research.