Which Disease Do I Have?

Q:  My doctor is treating me for RA, but he filled out a form saying I had "polyarthritis-seronegative." Can you tell me what this means?  

A:  A doctor diagnoses RA based on the findings of a medical history - symptoms you've been experiencing and how long, other medical problems you have or have had, a physical examination and medical tests, such as blood tests and X-rays. Although there is no single finding that confirms a diagnosis of RA, one of the most useful tests in the diagnosis is a blood, or serologic, test for rheumatoid factor. Rheumatoid factor is a particular autoantibody that often increases in people with RA. 

When rheumatoid factor is present, the serologic test is said to be positive. This serologically positive test result for rheumatoid factor is often shortened to the term "sero-positive." Most patients with RA will be "sero-positive." However, as many as 25 percent will be "sero-negative."

"Polyarthritis" means inflammation of many joints. RA is a form of arthritis involving multiple joints. Although RA is the most common form of polyarthritis, it is just one of many.

In the early phase of the disease, your doctor may not be able to give an exact diagnosis and will work with a preliminary diagnosis of polyarthritis. If the test for rheumatoid factor is negative -- as it often is early in the disease process -- the diagnosis may be "sero-negative polyarthritis." This term is not a specific diagnosis, but rather a description of the clinical features and associated laboratory findings. Pending the establishment of a firm diagnosis, many physicians will treat polyarthritis patients as they treat RA patients. 

GRANT CANNON, MD
Rheumatologist

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