Fibromyalgia: Diagnostic Criteria
In 1995, as an undergraduate, I was asked to put together a brief review of the literature on fibromyalgia. At the time, I knew little about fibromyalgia and absolutely nothing about ME/cfs. In my brief review, which I recently unearthed, I noted that there seemed to be multiple conceptions of fibromyalgia as well as a strange emphasis on psychological factors. Now, 25 years later, I have decided to take another look to see how our understanding of fibromyalgia has evolved.
This discussion is intended to take a historical look at the different diagnostic criteria that have been used to define fibromyalgia (FM), beginning with the current diagnostic criteria:
AAPT Diagnostic Criteria for Fibromyalgia (Arnold et al., 2018)
The current diagnostic criteria for fibromyalgia was defined in 2018 by an international working group consisting of clinicians and researchers with expertise in fibromyalgia. The working group was assembled by the American Pain Society (APS) and the U.S. Food and Drug Administration (FDA). It is the first set of diagnostic criteria put together by pain specialists, rather than by rheumatologists.
AAPT Diagnostic Criteria said:The [ACTTION-APS Pain Taxonomy (AAPT)] established an international [fibromyalgia (FM)] working group consisting of clinicians and researchers with expertise in FM to generate core diagnostic criteria for FM. [...] The process for developing the AAPT criteria and dimensions included literature reviews and synthesis, consensus discussions, and analyses of data from large population-based studies conducted in the United Kingdom. [...] Future studies will assess the criteria for feasibility, reliability, and validity.
So far, so good.
AAPT Diagnostic Criteria said:The multiple symptoms and comorbidities associated with FM make it difficult to diagnose, and FM is still underdiagnosed and undertreated. The diagnosis of FM might take >2 years, with patients seeing an average of 3.7 different physicians during that time.
AAPT Diagnostic Criteria said:The Fibromyalgia Working Group proposed a reduction in non-pain symptoms for inclusion [...] as core diagnostic criteria to reduce the complexity of diagnosis and make the FM criteria easier to use in practice. The Fibromyalgia Working Group identified fatigue and sleep problems as 2 key associated symptoms for several reasons. First, these symptoms, along with chronic pain, occur in most patients with FM. [...] Finally, responder definitions using fatigue and sleep problems, in combination with pain and physical function, were shown to be responsive to change in FM clinical trials.
So, in addition to "multi-site pain", both fatigue and sleep problems are now considered core diagnostic criteria for fibromyalgia. But what exactly do they mean by "fatigue"?
AAPT Diagnostic Criteria said:Fatigue is defined as physical or mental fatigue judged as at least moderate severity by the health care professional. Physical fatigue may manifest as a complaint of physical exhaustion after physical activity, including an inability to function within normal limits for activities that constitute normal daily activities and the requirement for rest periods after activity.
An "inability to function within normal limits for activities that constitute normal daily activities" - now this sounds familiar. A "requirement for rest periods after activity" - now this sounds even more familiar.
And what exactly do they mean by "sleep problems"?
AAPT Diagnostic Criteria said:Sleep problems are defined as difficulty falling or staying asleep, frequent awakening that is disturbing during a sleep period, or feeling unrefreshed after sleep.
So basically, insomnia and unrefreshing sleep.
They also clarify that a diagnosis of fibromyalgia does NOT exclude other, overlapping diagnoses:
AAPT Diagnostic Criteria said:The presence of other disorders does not necessarily exclude a diagnosis of FM, and all disorders will need clinical attention.
In addition to the core diagnostic criteria, they also list supporting diagnostic criteria.
AAPT Diagnostic Criteria said:Features that are not included in [core diagnostic criteria] but may be used to support a diagnosis of FM are described below. [...] Dyscognition (eg, trouble concentrating, forgetfulness, and disorganized or slow thinking) is increasingly recognized as a major feature of FM, with dysfunction being seen in working memory and executive function. [...] Environmental sensitivity or hypervigilance, manifesting as intolerance to bright lights, loud noises, perfumes and cold, is a common complaint of FM patients.
So, cognitive dysfunction (brain fog) is a "major feature" of fibromyalgia and hypersensitivities to light, sound, odors, etc. are "common complaints".
They then explicitly acknowledge the similarity to ME/cfs.
AAPT Diagnostic Criteria said:Chronic fatigue syndrome is a condition that has considerable overlap with FM, with the predominance of pain an identifier of FM.
But then they engage in the usual speculation about the role of psychological factors and comorbidities.
AAPT Diagnostic Criteria said:FM, especially the “primary” form, is also very comorbid with early life and current stress, and many, if not most, individuals will have a lifetime history of a psychiatric disorder such as depression or anxiety.
Finally, they acknowledge that their diagnostic criteria are not perfect, and that pain might not even be the most disabling symptom in fibromyalgia.
AAPT Diagnostic Criteria said:The challenge shared by all attempts to define criteria for FM is that there is no gold standard for FM diagnosis. [...] The AAPT taxonomy offers a new approach by defining core criteria and including other associated symptoms and signs, comorbidities, and impact on function in other dimensions. [...] Although pain is the main symptom of FM, other symptoms are reported to be clinically significant by patients and are sometimes more disabling than pain.
The actual diagnostic criteria are detailed in the following post.