Page 46 - Let them speak Towards a patient reported outcome measure set for

Chapter 2
acceptability among affected individuals. However, results might be difficult
to generalize or interpret. Furthermore, it is not feasible and desirable to use
condition-specific PROMs for more than 7000 rare disorders.59 It may also not
be necessary, as research has shown that PRO domains that patients consider
important are very similar among patient populations.37
Generic instruments have the advantage of allowing comparison of
outcomes between different disease (sub)groups. Generally, all individuals
want to feel and function well, such as living without symptoms and being
able to carry out daily activities. Feelings and functions can be affected
by different health conditions, and these can result to similar problems
with considerable overlap in relevant PROs across conditions, which
could be measured with one set of generic outcome measures across
conditions.36,37 Methodological innovations, such as item response theory
(IRT), have been used to develop PROMs with good measurement properties
that are applicable across different health conditions, such as Patient-
Reported Outcomes Measurement Information System (PROMIS®).60–62 IRT-
based item banks are large sets of calibrated questions measuring the
same construct, enabling efficient measurement through short forms or
computerized adaptive testing (CAT).41,63 This provides a valuable solution,
since redundant items for specific individuals will be minimized, increasing
relevance and efficiency.64
To ensure relevance, personalized outcome measurement instruments have
gained emerging interest, especially for rare and heterogeneous patient
populations since health manifestations are often specific, variable, and
complex.65 Instruments such as Goal Attainment Scaling enable focusing on
personal goals and abilities.66 Additionally, by including outcomes that are
specifically relevant to the affected individual, treatment adherence might
be enhanced as well.67 Also regulatory agencies have increasing interest in
the relevance of what is being measured,68 as treatment effects might be
statistically significant, but not clinically or socially relevant, or vice versa.69
Recommendations for selecting outcomes and instruments
In order to measure what matters to patients, several factors should be
taken into account when selecting outcome measurement instruments
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