27physical function that coincides with a deterioration in psychological well-being.
However, the brevity of summary items limits the specific inferences that can be
made about particular aspects of health. Responses to transition items may suffer
from recall bias and may be unduly influenced by current health status.
Utility Measures
Utility measures incorporate preferences or values attached to individual health
states and express health states as a single index. This type of instrument produces
evidence for the overall value of health states to society and can be used in cost-
utility analysis. The EuroQol EQ-5D consists of five items relating to mobility,
self-care, main activity, pain/discomfort, and anxiety/depression [ 20 , 21 ]. On the
basis of their responses to the five items, patients are classified into a health state
with a preference weight attached. Preferences for health states are derived from
general population surveys using techniques such as the rating scale, standard gam-
ble, and time trade-off. These techniques are sometimes used to obtain direct health
state values from patients.
Being a single index, this facilitates comparisons between treatments for differ-
ent health problems and is useful for economic evaluation including cost-utility
analysis. Utility measures are usually broad in their focus and are therefore subject
to the same criticisms as generic instruments. Some respondents have difficulty
understanding the nature of the experimental tasks they are required to perform.
Selecting a PROMs Instrument
Several types of instrument are available in the literature. In selecting an instrument,
users must consider the different types of tools that are available and how they meet
the requirements of the proposed aim. There are several ways to stratify the PROMs
instruments:
• Type—The simplest and most useful distinctive approach is to classify them into
generic, which can be widely applicable, and those specific to particular health
problems or populations. These instruments can be used in a number of applica-
tions including clinical trials, economic evaluation, and routine patient care.
• Mode—Different modes of instrument administration are presented, the main
forms being self-administered and interviewer-administered.
• Properties—Instrument selection should be based on a number of criteria includ-
ing certain psychometric properties such as reliability and validity, as well as
more general issues such as the appropriateness of an instrument for a specific
application.
2 A Guide to PROMs Methodology and Selection Criteria