The Prevalence Of Fibromyalgia In The General Population - a Comparison Of The ACR 1990, 2010 and Modified 2010 Classification Criteria

Background/Purpose: In 1990 the ACR published criteria for the
classification of fibromyalgia (FM), based on widespread pain and tenderness.
In 2010 new criteria were published which were based on widespread
pain and somatic symptoms and explicitly excluded individuals
that a clinician considered had a disorder that would otherwise explain
the pain. Then, in 2011, the 2010 criteria were modified (hereafter referred
to as the 2010m criteria) to allow their use in research, without the
requirement of a clinical history or examination. To our knowledge, there
have been no studies investigating the population prevalence of FM in a
manner that allows comparison between the three sets of criteria. The aim
of the current study was to determine the prevalence of FM in the general
population and, specifically, to compare differences in prevalence, when
using different criteria.
Methods: In the UK, 96% of the population are registered with a
general practitioner providing an ideal population sampling frame. Postal
questionnaires were sent to 4500 randomly selected individuals, aged
25yrs, registered with a general practitioner in the Grampian region,
Scotland (UK). The questionnaire included questions on pain and somatic
symptoms, and on prior rheumatological diagnoses: osteoarthritis, rheumatoid
arthritis, osteoporosis, SLE, scleroderma, ankylosing spondylitis
and gout.
All participants with chronic widespread pain, or who met the 2010m
FM criteria, were invited to attend a clinical research facility, as were a
random sample of participants who did not meet these criteria. At the
clinic, participants completed an additional questionnaire; and underwent
a full examination by a rheumatologist, including clinical history and
tender-point examination.
Using the information collected it was possible to classify participants
according to each of the ACR 1990, 2010 and 2010m FM criteria. The
population prevalence of each was determined by weighting back to the initial
general practice sample, by the inverse of the sampling fraction.
Results: 1604 (36%) participants returned a questionnaire, 269 participants
were invited, of whom 104 (39%) attended the clinical examination.
Of these, 32 met at least one of the FM criteria (31%). Weighting
back to the general population, the prevalence of FM using the ACR 1990,
2010 and 2010m criteria was 1.9% (95%CI: 0.8–3.1%); 1.2% (0.3–2.1%);
and 5.3% (4.7–6.0%), respectively. The gender ratio (female: male) varied
across criteria from 11.2 (1990) to 6.7 (2010) and 2.3 (ACR 2010m) and
56%, 29% and 48% of participants who met these criteria, respectively,
also reported the prior diagnosis of another rheumatological condition.
Conclusion: This is the first study to produce population estimates of
the prevalence of FM using the three different ACR classification criteria.
Prevalence estimates are considerably higher, and a greater proportion of
men are classified as having FM with the 2010m criteria in comparison to
either of the criteria requiring clinician input (1990 and 2010). Further,
depending on which set of criteria are employed, between one-third and
one-half of participants who meet the criteria have coexistant other
rheumatological disorders.