Performance outcomes of the PEDI-CAT for assessing functional ability in the population with leukodystrophy.

Cross-sectional design: all three assessments were completed within two weeks, so the study shows how the tools relate at one point in time, not whether the PEDI-CAT tracks change over months or years. Single centre (Children's Hospital of Philadelphia), which limits generalisability to other populations and settings. Small subgroups: Pelizaeus-Merzbacher disease had only 7 participants, so the low scores in that group are hard to interpret. Only English and Spanish versions of the PEDI-CAT were used, although more languages are now available. In-person administration only, so the results do not yet confirm the PEDI-CAT works the same way when completed remotely. The responsibility domain is designed for children aged 3 and older, but was completed for all participants regardless of age; most children scoring at the floor in this domain were under 3. About 25% of PEDI-CAT responses were flagged as inconsistent with the tool's algorithm, suggesting the standard item response theory model does not fully capture how this population's function is distributed.

Several authors have financial relationships with companies developing treatments for leukodystrophy and related rare neurological conditions. FG receives research support from Ionis Pharmaceutical. AG consults for Biogen and holds a licensing agreement with CHOP INTEND. ATW has received grants and clinical trial support from Ionis, Roche/Genentech, Novartis, Passage Bio, Sarepta, and Pfizer, and serves on a data safety board for SwanBio. AV receives research funding and consulting from Affinia, Sanofi, Takeda, Passage Bio, Ionis, Biogen, Eli Lilly, and others. LA receives research funds from Takeda, Orchard, Biogen, and Eli Lilly, and consults for Orchard. None of these relationships are with the maker of the PEDI-CAT itself, but they are in the same disease area.

Do not read the strong correlations as proof the PEDI-CAT replaces in-clinic assessment. This is a single-centre, cross-sectional study with no follow-up, and about a quarter of responses were flagged as inconsistent with the tool's algorithm, suggesting it does not fully capture how this population functions. The correlations show the two tools agree at one point in time; they do not show the PEDI-CAT tracks change the way the GMFM-88 or PDMS-2 do.