Fibromyalgia (FM) is a common chronic pain disorder that is difficult to diagnose. Over the years, various classification, diagnosis and screening criteria have appeared, but they are still under development, in light of scientific advances.
In the US, the Analgesic, Anesthetic, and Addiction Clinical Trial Translations Innovations Opportunities and Networks (ACTTION), together with the FDA and the American Pain Society (ACTTION-APS), initiated the Pain Taxonomy (AAPT) to develop a diagnostic system that is clinically useful and consistent in chronic pain disorders.
The AAPT formed an International Working Group for the study of FM, in order to establish basic diagnostic criteria and apply the multidimensional diagnostic framework adopted by AAPT for FM.
| Dimension 1 |
> Basic diagnostic criteria
Since 2011, the US College of Rheumatology (ACR) classification criteria only consider chronic widespread pain (e.g., pain in the left or right side, above or below the waist, axial skeletal pain [spine cervical or thoracic or chest, or lower back]) and tenderness (e.g., tenderness of ≥11 of 18 specific tender points on the body).
Subsequently, the definition of FM changed from being considered a predominantly chronic pain disorder to a multi-symptom disorder, eliminating the examination of spot tenderness as a requirement for diagnosis. But, this definition distances a bit from chronic pain.
The 2011 criteria do not consider the spatial distribution of painful sites while those published in 2016 require patients to show pain in 4 of 5 regions, called "widespread pain" to distinguish it from the 1990 definition of "widespread pain." Although there are different definitions of widespread pain and associated symptoms, most of the above FM criteria appear to identify a similar group of patients.
Based on the review of existing criteria, the FM Working Group consensus focused on designing core diagnostic criteria (dimension 1) that would reflect current FM knowledge, and practice, to be used by both clinicians and by researchers in clinical trials.
The AAPT multidimensional diagnostic framework allowed the Group to identify the core symptoms of FM and include other associated symptoms and signs in dimension 2. Group members agreed that dimension 1 would include only a core set of diagnostic symptoms and, that signs such as specific pain would be relegated to dimension 2.
> Definition of FM pain in dimension 1
It was agreed that dimension 1 should identify FM as a predominantly chronic pain disorder. After analysis of many diverse studies, the authors maintain that classification of pain simply by the number of self-reported sites distributed throughout the body, including joint sites, is sufficient to define FM pain. The number of pain sites needed to define FM was ≥8.
> Non-painful FM symptoms in dimension 1
The FM Working Group proposed reducing non-painful symptoms to include them in dimension 1, as basic diagnostic criteria, in order to reduce the complexity of diagnosis and facilitate the use of FM criteria in practice. This Group identified fatigue and sleep problems as 2 key symptoms associated with pain, for several reasons:
1. First, these symptoms, along with chronic pain, occur in the majority of FM patients.
2. Second, pain, sleep disorders, and fatigue were identified as core symptoms of FM.
Other non-painful symptoms and signs that are included in dimension 2 are recognized and can be considered when evaluating the patient, but it has not yet been established whether the presence or severity of fatigue is sufficient to establish a basic central diagnostic criterion for FM.
> Number of pain sites
According to the analysis of population data and the consensus of the FM Working Group, the proposed criteria for FM in Dimension 1 require that, of the 35 points that appear on the body manikin (used to identify painful points), ≥11 pain sites.
But, considering such a mannequin to be impractical for most doctors and researchers, the number of possible sites was reduced, which, in turn, were grouped together, keeping key body areas separate, such as arms and legs. This generated a new body mannequin with only 9 defined sites, which finally, after the analysis of other studies, resulted in a mannequin with 5 and 6 sites, depending on the study used.
> Duration of symptoms and presence of other disorders in dimension 1
When considering the duration of symptoms required for the diagnosis of FM, a duration of 3 months was approved by consensus because it better reflects the chronicity of FM. It was also accepted that the presence of other disorders or related pain symptoms do not rule out the diagnosis of FM, in line with the 1990-193 ACR criteria. However, as noted in the Bennett et al criteria, careful evaluation is recommended to identify any conditions that could fully explain the patient’s symptoms and/or contribute to the severity of the symptoms.
| AAPT Diagnostic Criteria for Fibromyalgia |
Dimension 1: Basic diagnostic criteria 1. Pain at multiple sites, defined as ≥6 pain sites out of a total of 9 possible sites (see figure) 2. Moderate to severe sleep problems or fatigue 3. Pain in multiple sites plus fatigue or sleep problems for at least 3 months |
| NOTE . The presence of another pain disorder or related symptoms does not rule out the diagnosis of FM. However, a clinical evaluation is recommended to evaluate any conditions that may account for the patient’s symptoms or contribute to symptom severity. |
Number of painful body areas. Patients are asked to check the areas where they feel pain on the 2 views of the manikins (ignoring previously shaded areas). Alternatively, patients can use the body site checklist. The number of separate sites is added from a maximum of 9 body sites.
| Differential diagnosis |
These new criteria for FM recommend that doctors evaluate the presence of other disorders so that appropriate treatments can be initiated.
This can be challenging in clinical practice because comorbid disorders, like other chronic pain disorders, are common in patients with FM. Several disorders can mimic FM, such as hypothyroidism and inflammatory rheumatic diseases.
On the other hand, some medications can contribute to pain, such as statins, aromatase inhibitors, bisphosphonates, and opioids (opioid-induced hyperalgesia). However, these conditions and many others (rheumatoid arthritis, osteoarthritis, systemic lupus erythematosus, spinal stenosis, neuropathies, Ehlers Danlos syndrome; sleep disorders, such as sleep apnea, and mood and anxiety disorders) also coexist in patients with FM.
The physician must determine the possible contribution of various disorders, which does not necessarily exclude the diagnosis of FM, and all disorders will require clinical attention, with corresponding studies. In general, extensive laboratory testing is not necessary to diagnose FM.
| Dimension 2 |
> Common features
There are characteristics that are not included in dimension 1 but that can be used to support the diagnosis of FM: a) generalized sensitivity of tissues and muscles to pressure that normally does not cause pain; It is a universal complaint and was coded as "tender point" in the 1990 ACR criteria. Although tender point assessment has been eliminated from the most recent criteria, it is still used.
A tender point examination, either as part of the ACR criteria above or as an abbreviated version, can provide valuable information to the clinician about the overall state of the patient’s condition, and support the diagnosis of FM; b) discognition (e.g., difficulty concentrating, forgetfulness, and disorganized or slow thinking) is increasingly recognized as an important feature of FM, with dysfunction in working memory and executive function.
- Self-reported questionnaires are useful for examination in patients with FM.
- Neuropsychological testing may be needed to delineate the extent of cognitive dysfunction.
In functional MRI images, patients with FM show less activation in the inhibition and attention networks and greater activation in other areas. Because inhibition and pain perception may utilize overlapping networks, resources used for pain processing may not be available for other processes.
All FM patients experience varying degrees of musculoskeletal stiffness , but such stiffness is difficult to distinguish from the stiffness of conditions such as rheumatoid arthritis, polymyalgia rheumatica, and ankylosing spondylitis.
The stiffness of FM is usually worse first thing in the morning and improves during the course of the day, but unlike that accompanying other conditions, it does not respond to corticosteroids. A common complaint of FM patients is sensitivity to environmental stimuli (intolerance to bright lights, loud noises, perfumes, cold). This is probably a central sensitization reflex.
| Symptoms and differentiating signs of the medical disorder |
> Rheumatological • Rheumatoid arthritis: predominant joint pain, joint swelling, morning stiffness >1 hour • Systemic lupus erythematosus: multisystem disease, joint/muscle pain, rash, photosensitivity, fever • Polyarticular osteoarthritis: joint stiffness, crepitation • Polymyalgia rheumatica: pain, weakness, stiffness in the proximal girdle of the shoulder and hip, common in the elderly • Polymyositis or other myopathies: weakness and proximal muscles • Spondyloarthropathy: cervical spinal pain, middle and anterior wall of the chest or lumbar regions, limited spinal mobility due to pain and stiffness • Osteomalacia: diffuse bone pain, fractures, proximal myopathy with muscle weakness > Neurological • Neuropathy; stabbing or burning pain, tingling, numbness, weakness • Multiple sclerosis: visual disturbances, ascending numbness in one leg or in the form of a band and trunk, dysarthria > Infectious • Lyme disease: rash, arthritis or arthralgia, in endemic areas • Hepatitis: right upper quadrant pain, nausea, hyporexia > Endocrine • Hyperparathyroidism: increased thirst and urination, kidney stones, nausea/vomiting, hyporexia, thinning bones, constipation • Cushing syndrome: hypertension, diabetes, hirsutism, lunar facies, weight gain • Addison’s disease: postural hypotension, nausea, vomiting, skin pigmentation, weight loss • Hypothyroidism: cold intolerance, mental slowness, constipation, weight gain, hair loss |
| Epidemiology |
The prevalence of FM varies from 5 to 12%, depending on the population sample and the verification method; It predominates in women and increases with age, but decreases after age 80. It begins between 30 and 50 years of age, but also occurs in children and adolescents, in whom there is a significant deterioration in physical function. Juvenile symptoms persist into adulthood.
| Dimension 3 |
> Common medical and psychiatric comorbidities
FM is associated with many comorbidities that can be categorized as other somatic pain disorders, psychiatric conditions, sleep disorders, rheumatic diseases and other conditions.
Many of these associations are thought to result from central sensitization , but this cannot explain all the associations. Chronic fatigue syndrome is a condition that has considerable overlap with FM; the predominance of pain identifies FM.
Among the somatic pain conditions that are associated with FM, the most recognized are irritable bowel syndrome, chronic pelvic pain and interstitial cystitis, chronic cephalic and orofacial diseases, such as temporomandibular disorder, otological symptoms, chronic headaches and migraine.
Psychiatric conditions that are associated with FM are major mood disorder (e.g., major depressive disorder and bipolar disorder), anxiety disorders (e.g., generalized anxiety disorders, panic disorders, post-traumatic stress disorders ; social phobia and obsessive-compulsive disorder) and substance abuse disorder.
Sleep disorders that may occur concomitantly with FM (obstructive and central sleep apnea, restless legs syndrome), various rheumatic conditions, both inflammatory and degenerative, may act as a generator of peripheral and FM-associated pain, including inflammatory rheumatic diseases such as rheumatoid arthritis, systemic lupus erythematosus, scleroderma, Sjögren’s syndrome and others, and osteoarthritis.
Joint hypermobility , as in joint hypermobility syndrome and Ehler Danlos syndrome, may predispose to recurrent pain followed by FM. The association with rhinitis and urticaria is especially interesting, because it expresses a common genetic profile. Obesity is common in patients with FM and is associated with more severe pain, poorer sleep, and reduced physical strength and flexibility.
| Dimension 4 |
> Neurobiological, psychosocial and functional consequences
Overall result including FM cost
FM symptoms usually persist over time. Many patients can identify strategies that help them moderate their symptoms. Of all the persistent symptoms, the most common is sleep disorder. In one study, FM patients’ healthcare costs were 3 times higher than controls.
| Morbidity and mortality |
In older European men, chronic widespread pain was associated with slower cognition and greater frailty, and a 1.25-fold increased risk of stroke in FM compared to controls, and a 2.3-fold increased risk in older subjects. youths.
Initial reports suggested that FM and chronic widespread pain were associated with increased mortality, including cancer and cardiovascular disease.
Although there has been variability between studies conducted, the largest study to have examined this (UK Biobank), combined in a meta-analysis, has confirmed that patients with chronic extended color have a significant excess risk of death.
As expected, expected suicidal ideation and suicide risk were mainly associated with depression and global mental health, and were much higher in patients with FM than in those with low back pain and controls.
| Dimension 5 |
> Putative psychosocial and neurobiological mechanisms; risk factors and protective factors
Risk factors and comorbidities
People who develop FM almost always have a history of chronic pain in various regions of the body, and central nervous system symptoms (fatigue, sleep, memory, and mood disturbances).
Often, individuals who eventually develop FM began their symptoms in childhood or adolescence and are more likely to experience headache, dysmenorrhea, temporomandibular joint disorder, chronic fatigue, irritable bowel syndrome, functional gastrointestinal disorders, interstitial cystitis/syndrome. painful bladder, endometriosis and other regional pain syndromes (especially back and neck pain).
Psychopathological conditions, especially depression and anxiety, are also seen, and there are several types of stressors: lifelong adverse events, medical illnesses (including infections), trauma, and psychosocial stressors.
| Pathophysiology |
Among the factors involved in the pathophysiology of FM, genetic changes that influence the serotonin, dopamine and catecholamine pathway have been proposed. The physiological hallmark of FM, pain centralization or central sensitization, is believed to be an increase in central pain processing.
Testing studies have identified multiple potential mechanisms that may be responsible for pain amplification in FM, including a decrease in the activity of descending analgesic pathways, an increase in pain facilitatory pathways, and a diffuse increase in pain processing. all sensory stimuli (not just pain).
It is believed that FM and related syndromes may represent the amplification of all sensory stimuli in the insula, which is the region that consistently shows the greatest activity in functional MRI, since this region is critical in sensory assessment. The “medial” and prefrontal brain regions are involved with the affective or motivational aspects of FM pain processing.
| Discussion |
For the new diagnostic criteria, FM is defined as a multi-symptom disorder and, according to the authors, attempts to define criteria show that there is no gold standard for the diagnosis of FM. Until the pathophysiology is better understood and biomarkers identified, diagnosis is based on patient report and clinical assessment.
Although the criteria published to date appear to identify a similar group of patients, the objective of the FM Working Group was to make the diagnosis of FM easier for the clinician, while at the same time being useful for researchers, and allowing the key symptoms of the disease to be captured. disorder.
The AAPT taxonomy offers a new approach by defining the basic criteria and including other associated symptoms and signs, comorbidities, and the impact on function in other dimensions. This taxonomy allows the doctor and researcher to focus on a limited number of basic symptoms for the diagnosis, which allows all other associated symptoms and signs to be included in dimension 2, to support the diagnosis of FM.
After analyzing several population studies, the FM Working Group established by consensus criteria to evaluate the definitions of widespread pain and determine the best combination of pain and symptoms, to better identify patients with FM. To this end, new criteria were developed for FM in dimension 1.
The Group determined that pain is the central symptom of FM and all patients must meet this criterion. Based on the results of data analysis from multiple population and other studies, they decreased the number of pain points required, regardless of their anatomical distribution (rather than generalized pain criteria).
Although pain is the primary symptom of FM, other symptoms reported by patients are clinically significant and are sometimes more disabling than the pain itself.
The new AAPT diagnostic criteria include 2 other symptoms, fatigue and sleep problems, which are most commonly reported by patients with FM. This simplified the criteria, so that we did not have to resort to scoring the associated symptoms. Problems identified by FM patients include: difficulty falling and staying asleep and non-restorative sleep.
To arrive at the diagnosis, by consensus, the Working Group focused on at least 6 of the 9 pain sites, combined with fatigue or sleep disorders. The primary objective of the AAPT was to develop the AAPT dimensions for FM.
In the process, the Group devised new basic criteria for the diagnosis of FM, supported by the analysis of data from a large-scale, population-based post hoc study. The use of a body manikin has become a standard way of collecting information on pain sites experienced by the subject, and has been shown to be valid and reliable.
Although the different studies analyzed have limitations, the data analysis demonstrated that the characteristics of FM could be defined in multiple ways.
| The consensus of the AAPT Working Group was to simplify the diagnostic criteria to facilitate the identification of FM in clinical practice and for research purposes. |
The authors conclude that chronic pain remains the main symptom of FM associated with 2 key symptoms, fatigue and sleep disturbances, and that its presence supports the diagnosis of FM. At the same time, it will be useful in all clinical settings, including primary, secondary and tertiary care, but also requires further study.
The taxonomic analysis of AAPT is multidimensional, making it unique compared to other existing and developing diagnostic criteria. More studies and revisions of the dimensions are needed to evaluate the prevalence of FM using the new definition.
