Page 223 - Let them speak Towards a patient reported outcome measure set for

General discussion
banks while preserving comparability with other disease groups and the
general population, which is a key strength of PROMIS.
Responsivity
Responsiveness is another key measurement property of a PROM, reflecting
its ability to detect change over time (46). This is essential when monitoring
individuals longitudinally, for example, to assess treatment efficacy or
track disease progression (49). As targeted therapies for individuals with
GID become more widely available (50), responsive PROMs are crucial for
evaluating the effect of these therapies on daily functioning. Responsive
PROMs are equally important in daily routine care. Healthcare professionals
need confidence that PROMs can capture changes. For instance, adults
with Down syndrome are at high risk of early-onset Alzheimer’s disease
(51), underscoring the importance of monitoring functional decline over
time. Responsiveness should also be assessed in line with the COSMIN
guidelines (48), and will be evaluated for the core PROM set in future work.
In addition to detecting change, it is essential to determine the smallest
change in symptoms or functioning that is meaningful for individuals with
GID, known as the minimal important change (MIC) (52). Establishing
the MIC is particularly important when evaluating treatment effects, as a
statistically significant change may not be necessarily clinically meaningful
if it is not perceived by the individual as relevant. A MIC is best established
using anchor-based methods, for example by asking individuals to rate their
perceived change on a 5- or 7-point Likert scale and relating these ratings to
the PROM change scores (mean change method) (53).
Adapting PROMs for individuals with ID
Following content validity assessment, particularly comprehensibility, it
may become clear that some items are not well understood by certain
groups. For example, by individuals with mild to moderate ID. In such cases,
adaptation of the PROM set is necessary to ensure that these individuals
can reliably report on their own health. Relying solely on proxy reports
may give an incomplete picture of the affected individual. Previous studies
have shown that proxies may rate patients’ symptoms and functioning
differently than patients themselves, particularly at individual level and for
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