Page 182 - Let them speak Towards a patient reported outcome measure set for

Chapter 7
To assess known-group validity, secondary analyses compared mean
PROMIS T-scores between individuals with and without ID, in line with
expected differences in health outcomes based on expert opinion (AvE) and
previous literature. We hypothesized that individuals with ID would score
lower on peer relationships/social roles and activities (55) and cognitive
functioning (only children, as the adult PROM primarily captures changes in
cognitive functioning instead of level of cognitive functioning), and would
score higher on anger (56, 57) and sleep disturbance (58). We expected a
mean difference of at least 3 points, corresponding to a previously defined
minimal important difference for PROMIS instruments (59).
GenID outcomes
To assess health and functioning in individuals with GenID, mean T-scores
of PROMIS CATs and SFs were calculated and reported. Mean T-scores
of caregivers of children were compared with US reference data from the
parent proxy population (60, 61), since Dutch reference data are not yet
available. Mean T-scores of adults were compared with Dutch reference
data from the adult population, or with US reference data if Dutch reference
data were not available (41, 43, 61-63). Mean T-scores of caregivers of
adults were not compared, as no reference data exists for this group.
Results
Participant characteristics
A total of 40 caregivers of GenID children, 37 GenID adults, and 44
caregivers of GenID adults participated in this study. Table 2 shows the
sociodemographic characteristics of the participants.
Reliability and efficiency
Tables 3 – 6 summarize reliability, number of items, and floor and ceiling
effects for the core PROM set (except for the single-item PROMs) and
subscales of the legacy questionnaires. All PROMIS CATs and SFs met
the reliability threshold (SE ≤ 3.2; 90% reliability; 4 – 13 items), except
PROMIS Anger for adults and caregivers of adults (both mean SE = 3.3;
89% reliability). More than half of the legacy subscales for caregivers of
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