How Are Polymyalgia Rheumatica and Giant Cell Arteritis Diagnosed?


A diagnosis of polymyalgia rheumatica is based primarily on the patient’s medical history and symptoms, and on a physical examination. No single test is available to definitively diagnose polymyalgia rheumatica. However, doctors often use lab tests to confirm a diagnosis or rule out other diagnoses or possible reasons for the patient’s symptoms.


The most typical laboratory finding in people with polymyalgia rheumatica is an elevated erythrocyte sedimentation rate, commonly referred to as the sed rate. This test measures inflammation by determining how quickly red blood cells fall to the bottom of a test tube of unclotted blood. Rapidly descending cells (an elevated sed rate) indicate inflammation in the body. While the sed rate measurement is a helpful diagnostic tool, it alone does not confirm polymyalgia rheumatica. An abnormal result indicates only that tissue is inflamed, but this is also a symptom of many forms of arthritis and other rheumatic diseases.


Before making a diagnosis of polymyalgia rheumatica, the doctor may order additional tests. For example, the C-reactive protein test is another common means of measuring inflammation. There is also a common test for rheumatoid factor, an antibody (a protein made by the immune system) that is sometimes found in the blood of people with rheumatoid arthritis. While polymyalgia rheumatica and rheumatoid arthritis share many symptoms, those with polymyalgia rheumatica rarely test positive for rheumatoid factor. Therefore, a positive rheumatoid factor might suggest a diagnosis of rheumatoid arthritis instead of polymyalgia rheumatica.


As with polymyalgia rheumatica, a diagnosis of giant cell arteritis is based largely on symptoms and a physical examination. The exam may reveal that the temporal artery is inflamed and tender to the touch, and that it has a reduced pulse.


Any doctor who suspects giant cell arteritis should order a temporal artery biopsy. In this procedure, a small section of the artery is removed through an incision in the skin over the temple area and examined under a microscope. A biopsy that is positive for giant cell arteritis will show abnormal cells in the artery walls. Some patients showing symptoms of giant cell arteritis will have negative biopsy results. In such cases, the doctor may suggest a second biopsy.