Differential item functioning in the Patient Reported Outcomes Measurement Information System Pediatric Short Forms in a sample of children and adolescents with cerebral palsy.

The cerebral palsy sample had more males and a smaller proportion of younger participants than the PROMIS calibration sample. The cerebral palsy sample included 107 individuals above the age range represented in the PROMIS calibration sample. The cerebral palsy sample excluded children who could not read, understand, and respond to items, and those whose primary language was not English. The two cerebral palsy samples used different completion methods, tablet with a team member present or interview in person or by phone, which may have affected responses. The cerebral palsy sample included more participants with higher mobility functioning, with more than 80% ambulatory and 16% using a walking device. The study compared item functioning, not patient outcomes after treatment, so it does not show that any therapy changes PROMIS scores.

The authors stated that they had no interests which might be perceived as posing a conflict or bias.

Do not read this as proof that PROMIS Mobility and Pain Interference scores are invalid for every child with cerebral palsy. The study found that some items behaved differently and says the meaning of total scores is unclear. It recommends checking how children interpret the items, not abandoning the measures.