FMS Underdiagnosed, Especially in Men

Fibromyalgia syndrome (FMS) can be a difficult to diagnose and treat illness. There is no laboratory test to confirm its presence and many fibromyalgia symptoms — pain, fatigue, and sleep, memory, and mood problems — can overlap with or be mistaken for other conditions. Consequently, a new study from the Mayo Clinic suggests that FMS is substantially underdiagnosed in many persons with the disorder, especially men.

For their study, Ann Vincent, MD, and colleagues focused on Olmsted County, Minnesota, where there is a comprehensive medical records pool known as the Rochester Epidemiology Project [Vincent et al. 2012]. Olmsted County encompasses a small area in southeastern Minnesota with Rochester roughly at its center and an area population of about 145,000 persons.

The researchers used two methods for estimating numbers of persons over age 21 with FMS:

• The first method was a retrospective review of medical records of potential cases of FMS using Rochester Epidemiology Project data from January 1, 2005 to December 31, 2009. This allowed an estimate of the prevalence of diagnosed FMS in everyday clinical practices.
  
  
• The second method was a random survey of adults in Olmsted County using the 2010 American College of Rheumatology's (ACR) fibromyalgia research survey criteria to estimate the percentage of responders who met FMS criteria. The self-reported criteria involve questions about the hallmarks of fibromyalgia: widespread pain and tenderness, fatigue, feeling unrested after waking, problems with memory or thinking clearly, and depression or anxiety, among other symptoms.

Writing online in the journal Arthritis Care & Research, the researchers report that, of the 3,164 potential FMS patients assessed by the first method, only 1,115, or about 35%, had a fibromyalgia diagnosis documented in medical records by health care providers. The age- and sex-adjusted prevalence of diagnosed fibromyalgia in the entire population by this method was estimated to be 1.1%.

By the second method, of the 2,994 people who received the survey by mail, 830 (≈28%) responded and 44 (5.3%) met FMS research survey criteria. Only 12 of these persons had been diagnosed with FMS by a healthcare provider. The age- and sex-adjusted prevalence of fibromyalgia in the general population of Olmsted County by this method was estimated at 6.4%.

Compared to men, the age-adjusted prevalence rates of FMS were significantly higher for women using both methods. In women, the survey-based prevalence of FMS was 3 times greater than the clinically diagnosed rate; whereas, in men, the difference was far greater — survey-based FMS prevalence was 20-fold higher than clinically diagnosed cases. Overall, the researchers conclude that many persons, particularly men, who might satisfy research criteria for FMS are unlikely to be diagnosed with the disorder.

COMMENTARY: The researchers caution that the two distinct prevalence rates — ie, medical diagnosis rate of FMS in the community (1.1%) and percentage of people who self-report symptoms meeting FMS criteria (6.4%) — should be interpreted within the context of the particular methodology. However, the data do suggest that FMS is being significantly underdiagnosed by healthcare providers and especially so when it comes to male patients.

One possible explanation provided by the researchers is that men do not seek medical care as frequently as women and, if tender points are used as a diagnostic criteria for FMS, men may not be as sensitive or responsive on this measure. Alternatively, healthcare providers simply may be less likely to consider and diagnose FMS in men with musculoskeletal pain and fatigue than in women.

According to background information in the Vincent et al. report, prior prevalence estimates of FMS in the United States general population were 3.4% in women vs. 0.5% in men (2% overall). A Canadian study estimated a 3.3% FMS prevalence (4.9% women, 1.6% men), and the prevalence of FMS in 5 European countries was estimated at 4.7%. The geographic disparities may reflect differences in populations, study designs, and measurements used.

In an earlier UPDATE article [here] we suggested that FMS may affect up to 4% of the U.S. population, but an estimated 70% may be misdiagnosed or undiagnosed. In one survey of persons with FMS, more than three-quarters of respondents (77%) had waited up to 3 years before seeking help from a healthcare professional; 70% reported that they hesitated to visit a healthcare professional because they thought their symptoms would simply go away. These trends appear to support the possibility of a high prevalence of undiagnosed FMS in community samples, as Vincent et al. suggest.

However, there were many limitations of this study by Vincent and colleagues. For one thing, the field survey assessed self-reported symptoms that may meet “survey criteria” for FMS, but these do not necessarily denote “clinical criteria” that can be better detected during face-to-face assessments by knowledgeable practitioners. Plus, there may have been biases in terms of who responded to the survey; so, the 6.4% figure may be overstated to a degree.

The other approach, reviewing pre-existing medical records, was limited to the information recorded at the time of clinical assessments. The researchers examined all records for the presence of widespread chronic pain and tender points, among other criteria; however, in some cases such data may have been insufficient or inaccurate.

Finally, there always is a question regarding the external validity of localized epidemiological studies such as this — that is, whether the results would be equally relevant for other regions of the U.S. or even in other countries. The study team concedes that more research is needed, particularly investigating why men who report FMS symptoms seem to be much less likely than women to receive a fibromyalgia diagnosis.

FOR ADDITIONAL INFORMATION regarding the most current approaches to fibromyalgia diagnosis, including clinical and patient self-assessment scoring forms, see…
> Boomershine CS. Fibromyalgia Diagnosis: Moving Beyond Tender Points. Pain Med News. 2012(Dec);10(12):50-56 [PDF here].
> Leavitt SB. A Better Way to Diagnose Fibromyalgia Proposed. Pain-Topics UPDATES. 2010(Jun) [article here].

REFERENCE: Vincent A, Lahr BD, Wolfe F, et al. Prevalence of fibromyalgia: A population-based study in Olmsted County, Minnesota, utilizing the Rochester Epidemiology project. Arthritis Care & Research. 2012; online ahead of print [abstract here].

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