180
Complex Constructs
Finally, FMS poses a challenge for measurement as it holds very complex con-
structs among its symptoms. Above all, cognitive impairment, recently added to the
ACR diagnostic criteria [ 65 ], remains as the least assessed and treated FMS domain.
This is the case both in general clinical practice and in research. This has been
attributed , mainly, to the expertise and time required for neuropsychological tests
for the different aspects of this domain, which includes attention, memory, process-
ing speed, recognition, etc.
Available PROMs in FMS
PROMs are critical in FMS due to the challenges previously noted. Without the
existence of these questionnaires it would be complicated to monitor evolution,
progression, and treatment of FMS.
OMERACT established in 2004 the key domains for the measurement of FMS:
pain, patient global assessment, fatigue, health-related quality of life, function (mul-
tidimensional), sleep, depression, and treatment side effects. Other important
domains, not considered as essential, included physical function, tender point inten-
sity, dyscognition, anxiety, and clinician global assessment [ 20 ]. In 2012 (OMERACT
9), the core-set fi nally included pain, fatigue, tenderness, overall patient, multidi-
mensional function, and sleep disturbance [ 21 , 23 , 66 ] (see Fig. 7.1 ).
A wide variety of instruments have been used in FMS. Many of them were devel-
oped for generic use or have been borrowed from other clinical populations. The
number of available PROMs specifi cally developed for FMS is surprisingly low for
a syndrome that is so subjective. The existing instruments will be commented upon
in detail and all are available at the EULAR Outcomes Measure Library [ 67 ]. They
cover a wide range of domains and constructs as they are summarized in Table 7.1.
Fibromyalgia Impact Questionnaire
The Fibromyalgia Impact Questionnaire (FIQ) is a self-administered questionnaire
with ten items that measure multiple domains of the FMS, such as the ability to
perform large muscle tasks, work diffi culty, pain, fatigue, morning tiredness, stiff-
ness, anxiety, and depression [ 68 , 69 ] (Appendix 1). It yields a score from 0 to 100,
with higher scores indicating greater impact. It is widely used, probably due to its
easiness of use and because it is free of charge. The FIQ has been validated in more
than 46 languages, as it was the fi rst PRO designed especially for FMS. As a limita-
tion, it can underestimate the severity of the patient, as items that are not marked are
deleted from the calculation; in addition, the FIQ has a gender bias, as it was
L. Carmona et al.