Fibromyalgia: What Clinicians Need to Know
Fibromyalgia (FM) is a syndrome manifested by widespread pain, stiffness, fatigue, cognitive difficulties (“fibrofog”), and non-refreshing sleep. Despite numerous articles, revised diagnostic guidelines, and FDA-approved medications, there are still physicians who believe that the disorder is not real and consider it a “wastebasket” diagnosis—given when no other pathological entity is found.
In ICD-9, there is no specific diagnosis for FM (or myofascial pain syndrome; both would fall under myositis). For many clinicians in the field, this represents a lack of “respect” for the diagnosis.
Much has changed about our understanding of the etiology of FM since the beginning of this millenium. The disorder now is considered a central sensitivity syndrome (CSS) because of its basic neurophysiological etiology. This makes FM a neurosensory disorder associated with difficulties with pain processing by the central nervous system (CNS).1,2
This also ties FM, which is estimated to effect 2% to 5% of the population, to other similar, if not overlapping, conditions, including chronic fatigue syndrome, interstitial cystitis, irritable bowel syndrome, vulvodynia, post-traumatic stress disorder, and others.3 Some groups also classify migraine as a CSS. However, migraine has an apparent physiologic basis (with a possible generator in the trigeminal nucleus caudalis) and is relieved by medications (triptans), which work via specific serotonergic receptor agonists (5-HT1BDF); this does not occur in a true CSS.
FM also may overlap with other regional pain syndromes, as well as anxiety and mood disorders, which may lead to incorrect primary diagnoses. FM may be considered primary or secondary to an associated disorder, such as systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), and chronic hepatitis C infection. It is important to identify the primary and the secondary clinical issue. For example, the treatment for the primary cause (SLE or RA) also will enable appropriate treatment of FM.
Still, FM may be a diagnosis of exclusion, and entities that can cause similar symptoms must be looked for and/or ruled out. This article will review the recent research into the diagnosis and etiology of FM, as well as updated treatment guidelines.
The diagnosis of FM is made both by the art and science of medicine. The basic signs and symptoms of FM include persistent (≥3 months) widespread pain (tenderness/pain on both sides of the body, above and below the waist, including the axial skeletal spine), along with stiffness, fatigue, non-refreshing sleep, cognitive difficulties, and many other unexplained symptoms, including anxiety and/or depression as well as loss of the ability to perform activities of daily living (ADL). Table 1 reviews the evolution of FM diagnosis.
In 1990, the American College of Rheumatology (ACR) endorsed a set of diagnostic criteria for FM developed by a group of researchers led by Frederick Wolfe, MD.4 The criteria originally were developed for recruiting patients for clinical studies and included a physical examination as well as tender point testing (typically 11/18 active symmetrical tender points was considered “positive”). Critics noted that the ACR 1990 criteria made it more difficult to accurately diagnose patients with FM.5
Objections to the physical examination led the ACR to revise its diagnostic criteria in 2010.6 The goal of the new criteria was to create a simple, practical guide for the clinical diagnosis of FM that could be used in a community setting. It included 2 scales, the widespread pain index (WPI), which allowed patients to describe where in the body it hurt, and the symptom severity scale (SSS), which measured fatigue, daytime sleepiness, somatic symptoms, and cognitive problems.
The 2010 ACR guidelines were further modified in 2011 (2011ModCr), at which time the physician estimate of somatic symptoms was eliminated and the WPI and SSS were expanded.7 The new 0-31 FM symptom scale (FS) included 19 pain locations and 6 self-reported symptoms, including difficulty sleeping, fatigue, poor cognition, headache, depression, and abdominal pain.6
To evaluate the validity of the new scale, Wolfe et al administered a questionnaire to 729 patient previously diagnosed with FM, 845 with osteoarthritis (OA) or with other noninflammatory rheumatic conditions, 439 with SLE, and 5,210 with RA. The authors found a score ≥13 correctly classified 93% of patients (sensitivity, 96.6%; specificity, 91.8%).
To further study the new questionnaire, Bennett et al performed a study to help validate the 2011ModCr.8 The research team studied chronic pain and psychiatric patients from various sites in the US. The study of the 2011ModCr found diagnostic sensitivity of 83.5% and specificity of 67.2%; and correctly classified 73.8% of patients with FM compared with the 1990 criteria. An alternate criteria (2013MedCr) was less sensitive (80.7%) but had higher specificity (79.6%); it classified 80.1% of patients correctly.8
Both the 2011ModCr and 2013ModCr found an increased prevalence of FM in men (16% for 2011ModCr and 14% for the 2013AltCr), as compared with that found with the ACR 1990 criteria (6%).8 An example of the current diagnostic questions/criteria taken from the Fibromyalgia Network.9
Although the new ACR criteria do not specify the need for a physical examination in the diagnosis of FM, it is appropriate. It also would be appropriate to assess tenderness, but a formal tender point examination is not required, nor “counted” in the diagnostic criteria.
There are no specific lab markers available to diagnose FM. When a clinician obtains a history that gives a possible indication of specific problems, that information should be explored using further tests. Table 2 lists the blood tests typically ordered by the author. In addition to the tests listed, the author orders rheumatoid factor, depending on any leading history or signs/symptoms. Although not totally verified, genetic markers (HLA-B27, HLA-B51, and FMF) may be considered based on clinical suspicion, but they should not be used to “rule-out” the diagnosis if the 2011ModCr indicate it. Epigenetics developed a blood test to diagnosis FM (FM/a test), but questions have been raised about inconclusive test results and undue influence by the manufactuerer.10 Experts such as Wolfe do not consider the test to be diagnostic of FM.11