Fibromyalgia

Tests

Fibromyalgia is difficult to diagnose. Unlike rheumatoid arthritis or osteoarthritis, fibromyalgia produces no visible physical changes. Until recently, the lack of physical evidence had led many doctors to suspect a psychological basis for the symptoms. Despite the absence of any physical or laboratory evidence, fibromyalgia is a physical disorder.

Tender points. In 1990, the American College of Rheumatology developed a set of criteria to diagnose fibromyalgia. Widespread pain, present for at least three months, must be located on both sides of the body, both above and below the waist. Pressure of about 9 pounds applied to at least 11 of 18 tender points must produce pain. To apply the same amount of pressure at each point tested, the doctor may use an instrument called a dolorimeter. In most cases, the pain is not just mild discomfort but acute pain that may cause a person to flinch or cry out.

It was once thought that pressure on areas of the body as close as 1 inch away from the tender points would not cause pain in people with fibromyalgia and that this specificity of location would help to confirm the diagnosis. However, recent research has not supported this belief. While not part of the official criteria, reports of fatigue and, in particular, of nonrestorative sleep help confirm the diagnosis.

Laboratory tests. Because the symptoms of fibromyalgia are similar to those of many other disorders, several tests may be done to rule these out. The doctor may perform blood tests to check for an underactive thyroid, rheumatoid arthritis, lupus, Lyme disease, and polymyalgia rheumatica (a disorder that causes stiffness and aching in the neck, shoulder, and hip areas). Imaging tests such as magnetic resonance imaging (MRI) may not be used initially, since they are expensive and sometimes associated with misleading results.

People who suspect they have fibromyalgia should consult a doctor who has experience with this syndrome. A rheumatologist is usually the best type of doctor to see.