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.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/the-prevalence-of-fibromyalgia-in-the-general-population-a-comparison-of-the-acr-1990-2010-and-modified-2010-classification-criteria/