Rheumatoid arthritis can be difficult to diagnose in its early stages for several reasons. First, there is no single test for the disease. In addition, symptoms differ from person to person and can be more severe in some people than in others. Also, symptoms can be similar to those of other types of arthritis and joint conditions, and it may take some time for other conditions to be ruled out as possible diagnoses. Finally, the full range of symptoms develops over time, and only a few symptoms may be present in the early stages. As a result, doctors use a variety of tools to diagnose the disease and to rule out other conditions:

Medical history:This is the patient's description of symptoms and when and how they began. Good communication between patient and doctor is especially important here. For example, the patient's description of pain, stiffness, and joint function and how these change over time is critical to the doctor's initial assessment of the disease and his or her assessment of how the disease changes.

Physical examination: This includes the doctor's examination of the joints, skin, reflexes, and muscle strength.

Laboratory tests: One common test is for rheumatoid factor, an antibody that is eventually present in the blood of most rheumatoid arthritis patients. (An antibody is a special protein made by the immune system that normally helps fight foreign substances in the body.) Not all people with rheumatoid arthritis test positive for rheumatoid factor, however, especially early in the disease. And, some others who do test positive never develop the disease. Other common tests include one that indicates the presence of inflammation in the body (the erythrocyte sedimentation rate), a white blood cell count, and a blood test for anemia.

X rays:X rays are used to determine the degree of joint destruction. They are not useful in the early stages of rheumatoid arthritis before bone damage is evident, but they can be used later to monitor the progression of the disease.