How is fibromyalgia diagnosed?

There is no blood or X-ray test to help the doctor determine whether someone has fibromyalgia. Therefore, the diagnosis of fibromyalgia is made purely on clinical grounds based on the doctor's history and physical examination. In patients with widespread body pain, the diagnosis of fibromyalgia can be made by identifying point tenderness areas (typically, patients will have at least 11 of the 18 classic tender points), by finding no accompanying tissue swelling or inflammation, and by excluding other medical conditions that can mimic fibromyalgia. Many medical conditions can cause pain in different areas of the body, mimicking fibromyalgia. These conditions include

• low thyroid hormone level (hypothyroidism),



• parathyroid disease (causing elevated blood calcium level),



• muscle diseases causing muscle pain (such as polymyositis),



• bone diseases causing bone pain (such as Paget's disease),



• elevated blood calcium (hypercalcemia),



• infectious diseases (such as hepatitis, Epstein Barr virus, AIDS), and



• cancer.

Even though there is no blood test for fibromyalgia, blood tests are important to exclude other medical conditions. Therefore, thyroid hormone and calcium blood levels are obtained to exclude hypercalcemia, hyperparathyroidism, and hypothyroidism. The blood alkaline phosphatase (a bone enzyme) level is often raised in patients with Paget's disease of the bone. The CPK (a muscle enzyme) level is often elevated in patients with polymyositis, a disease with diffuse muscle inflammation. Therefore, obtaining alkaline phosphatase and CPK blood levels can help the doctor decide whether Paget's disease and polymyositis are the causes of bone and muscle pains. A complete blood count (CBC) and liver tests help in the diagnosis of hepatitis and other infections.

Fibromyalgia can occur alone or in association with other systemic rheumatic conditions. Systemic rheumatic conditions refer to diseases that can cause inflammation and damage to numerous different tissues and organs in the body. Systemic rheumatic conditions associated with fibromyalgia include systemic lupus erythematosus, rheumatoid arthritis, polymyositis, and polymyalgia rheumatica. Blood tests which are helpful in evaluating these diseases include erythrocyte sedimentation rate (ESR), serum protein electrophoresis (SPEP), antinuclear antibody (ANA), and rheumatoid factor (RF). In patients with fibromyalgia without associated systemic illnesses, the ESR, SPEP, ANA, and RF blood tests are usually normal.