Exercise and antidepressants improve fibromyalgia

Journal of Family Practice, April, 2004 by Anna Quisel, James Gill, Dene Walters

Practice recommendations

* Fibromyalgia is diagnosed based on a patient's report of widespread pain of 3 months' duration or longer, and identification of 11 of 18 possible tender points (C).

* Fibromyalgia is functionally disabling and diminishes well-being; therefore, supportive care and evidence-based interventions should be offered (C).

* Aerobic exercise and antidepressants have been shown to moderately relieve symptoms of fibromyalgia in the short term (A).

When patient complains of pain "all over, consider fibromyalgia, which typically causes a well-documented pattern of pain and characteristic points of tenderness observable on physical exam. Once alternative diagnoses have been ruled out, offer the patient a 2-pronged therapeutic regimen that has proven successful at moderately relieving symptoms.

* FIRST RULE OUT CONCOMITANT OR MIMICKING DISORDERS

Consider the differential diagnosis carefully. (1) A person who meets the criteria for fibromyalgia may have yet another cause of chronic pain, such as rheumatoid arthritis, or may instead have a different treatable condition that mimics fibromyalgia.

Drug-induced myopathy. Pain suggestive of fibromyalgia should prompt a review of the patient's medicines. Drug-induced myopathy may occur in persons taking colchicine, statins, corticosteroids, or antimalarial drugs.

Connective tissue, autoimmune, and rheumatologic disorders. Consider this group of disorders next. In 1 study, one fourth of persons referred to a rheumatology clinic with presumed fibromyalgia instead had a spondyloarthropathy. (2)

Dermatomyositis and polymyositis may present with muscle pain and tenderness but, unlike fibromyalgia, cause proximal muscle weakness.

Systemic lupus erythematosus, rheumatoid arthritis, and polymyalgia rheumatica can also lead to widespread pain.

Blood tests such as antinuclear antibody (ANA), C-reactive protein, or erythrocyte sedimentation rate (ESR) may prove helpful when a patient has a history of unexplained rashes, fever, weight loss, joint swelling, iritis, hepatitis, nephritis, or inflammatory back pain (onset before age 40, insidious onset, present for more than 3 months, associated with morning stiffness, improvement with exercise). (3) In the absence of these signs, ANA, rheumatoid factor, and ESR testing in persons with fatigue and diffuse musculoskeletal pain have low positive predictive value. (4) The rate of false-positive ANA results may be as high as 8% to 11%, especially at low titers. (5,6)

Hypothyroidism. Widespread musculoskeletal pain has also been associated with hypothyroidism (level of evidence [LOE]: 2, case-control design), (7,8) supporting the inclusion of a thyroid-stimulating hormone in the work-up of fibromyalgia (strength of recommendation [SOR]: B). More recent research suggests that musculoskeletal pain is more related to thyroid microsomal antibodies than to hypothyroidism, (9) but there has been no further evaluation of antithyroid antibodies in persons with fibromyalgia.

* DIAGNOSIS: MOSTLY BY CLINICAL JUDGMENT

Persons with fibromyalgia have widespread pain, often worst in the neck and trunk. (1) Additional symptoms include fatigue, morning stiffness, waking unrefreshed, paresthesias, and headache. (1,10-15) (See "The toll of fibromyalgia.")

Accepted criteria

The diagnosis of fibromyalgia is based on 2 criteria:

1. A patient's report of widespread pain (right and left sides of the body, above and below the waist, and including the axial skeleton) persisting for at least 3 months

2. The clinician's identification of at least 11 of 18 potential tender points as specified in the American College of Rheumatology (ACR) 1990 Criteria for the Classification of Fibromyalgia (Figure) (LOE: 3, case-control design, nonindependent reference standard). (1)

These criteria do not exclude persons with rheumatic diseases or other chronic pain conditions. (1,37-39)

Caveats with the criteria

Despite these well-defined criteria, the diagnosis is not as clear-cut as it may appear. In 1990, the ACR convened a panel of 24 experts to define and standardize the diagnosis of fibromyalgia. The basis for this consensus was a group of 293 patients with fibromyalgia, each of whom had been assessed by one of the expert investigators according to "his or her usual method of diagnosis." (1)

The investigators determined the unique characteristics of fibromyalgia by comparing the 293 cases to 265 controls who had other chronic pain conditions (eg, low back pain syndromes, neck pain syndromes, regional tendonitis, possible systemic lupus erythematosus, rheumatoid arthritis). The investigators considered a multitude of symptoms and signs including sleep disturbance, morning stiffness, paresthesias, irritable bowel syndrome, fatigue, and anxiety. Their conclusion was that widespread pain and tender points were the most sensitive (88.4%) and specific (81.1%) distinguishing criteria for fibromyalgia. (1)

No reference standard. However, these calculations of sensitivity and specificity are less meaningful than in studies where an independent reference standard or gold standard is available. The ACR expert panel derived the criteria in a circular way using a nonindependent reference standard--ie, patients thought to have fibromyalgia compared with control patients thought not to have fibromyalgia. The expert panel essentially set the specificity of the criteria at 100%, since the specificity is based on the rate of false positives.