Finding Functionality: Rasch Analysis of the Functionality Appreciation Scale in community-dwelling adults including adults with spinal cord injury and neuropathic pain in the US

The Functionality Appreciation Scale (FAS) measures an individuals appreciation for the functions their body can perform, regardless of the individuals physical limitations. To facilitate the use of this tool by researchers and clinicians, it is necessary to understand what normal scoring looks like in healthy adults, as well as validate the scoring of this scale. We analyzed the FAS using Rasch Measurement Theory. FAS responses, demographic data, and clinical questionnaires were collected by the Brain Body Mind Lab (University of Minnesota) from 567 community-dwelling adults recruited at the Minnesota State Fair, including 14 adults with spinal cord injury. We evaluated item and person fit, targeting, unidimensionality, person separation reliability (PSR), local item dependence (LID), and differential item functioning (DIF) for demographic and clinical characteristics. We found a significant ceiling effect (26.98%) and a positive person mean location of 3.28{+/-}2.10 logits, indicating the FAS is too easy for the community-dwelling adults in the US. PSR was 0.79, indicating a capacity to differentiate groups of people according to their ability level of functional appreciation. We also compared the person mean location of adults who did or did not participate in body awareness training. Adults who practiced body awareness training had a higher person mean location (4.28, Interquartile Range [IQR] = 3.96 logits) than those who did not (2.73, IQR = 3.34), indicating a higher functionality appreciation. Overall, FAS demonstrated good item and person fit, but the current version of FAS will require more difficult items to be added to improve the targeting of the scale for use in a general population.