An accurate and early diagnosis of rheumatoid arthritis is necessary to rule out alternative explanations for your symptoms and to guide early treatment. Your health care provider will ask about your symptoms and past medical history.
If you have significant joint pain, it is important that you have a physical examination with a detailed joint examination by an experienced health care provider. Significant joint pain is pain that lasts more than a few days, causes swelling or reduces your ability to function. Symptoms and blood test results can suggest a diagnosis of rheumatoid arthritis (or another form of arthritis), but a physical examination that includes a detailed joint exam is the best way to be sure.
Rheumatoid arthritis cannot be diagnosed by a blood test alone. But an abnormal antibody called rheumatoid factor is present in the blood of 70 percent to 80 percent of people who have this disease. Rheumatoid factor is also present in the blood of 5 percent or more of healthy people, in people with diseases other than rheumatoid arthritis and in elderly people. For this reason, the presence of rheumatoid factor can only suggest — but cannot confirm — a diagnosis of rheumatoid arthritis.
High levels of rheumatoid factor are, on the other hand, associated with more severe arthritis. Health care providers use the presence of rheumatoid factor to support a diagnosis suggested by other findings. It is also one way to describe and predict the severity of the disease for an individual patient. It is not used as a screening tool to identify people with the disease.
A newer antibody test called anti-cyclic citrullinated protein (anti-CCP) has become a popular test to order for people with suspected rheumatoid arthritis. While it is found in only 50 percent to 70 percent of people with rheumatoid arthritis, it tends to be more specific than rheumatoid factor; that is, it is quite rare for someone to have this antibody without rheumatoid arthritis.
Your health care provider is likely to ask for additional blood tests to assess your blood counts, to evaluate the function of your kidneys and liver and to help identify other explanations for your joint pain. The results of these tests are important when considering the choices and doses of various drugs. For example, abnormal results on liver tests could indicate that your joint pain is a consequence of hepatitis (rather than rheumatoid arthritis) or that you are at increased risk of side effects from drugs known to affect the liver.
Joint fluid (also called synovial fluid) may accumulate in the joints in some forms of arthritis. Joint fluid that accumulates in the knee is often called "water on the knee." A sample of joint fluid can be withdrawn from the joint and tested for signs of inflammation, as indicated by a higher-than-normal number of white blood cells. Inflammation is usually present when the fluid is a result of rheumatoid arthritis. Joint fluid also may be tested for other signs of inflammation, infection or other disorders, including gout.
X-rays are not usually helpful to diagnose early rheumatoid arthritis because at that point they tend to show only what already has been observed in the physical exam (such as swelling or extra fluid). X-rays can be used, however, to confirm a diagnosis later in the disease. X-rays may reveal abnormalities of the joints, including damage in the bones near the joint (erosions), reduced bone thickness near the joint (osteopenia) and joint narrowing (resulting from cartilage loss). X-rays are used primarily to determine the degree of joint damage and to monitor the effectiveness of treatment. Bone scans and magnetic resonance imaging (MRI) also may be used, but these are not routinely performed to diagnose rheumatoid arthritis. One exciting area of research is evaluating the accuracy of MRI or other imaging techniques (including ultrasound) to identify early rheumatoid arthritis.
You may have heard about certain criteria that health care providers use to establish a diagnosis of rheumatoid arthritis. These were established for research purposes, and to be included in a study of rheumatoid arthritis, you must have four of seven of these criteria.
In actual practice, many health care providers use these criteria as a guide to diagnosis. It is important to recognize that these criteria were devised to make research studies easier to compare, not for individual patients seeking a diagnosis. Some people with rheumatoid arthritis do not meet these criteria, especially when their disease is mild. And some people meet these criteria but don't have rheumatoid arthritis. For example, patients with lupus may meet these criteria. Thus, your diagnosis will be based on a combination of your symptoms and your physical examination and test results.
A functional assessment is a critical part of evaluating rheumatoid arthritis. This assessment focuses on simple activities performed on a daily basis, called activities of daily living (ADLs). ADLs include dressing, preparing and eating meals, walking up or down stairs, bathing and so on. These activities are such an essential part of everyday life that it is easy to take them for granted. But if you have difficulty performing ADLs, your quality of life will probably suffer.
Your ability to perform ADLs and the amount of pain you have are two important measures that you can use to assess your rheumatoid arthritis. Assessing these measures on your own and communicating this to your health care provider will help him or her confirm the diagnosis, choose initial treatment and monitor your progress over time.
Once you have been diagnosed with rheumatoid arthritis and have started treatment, your health care provider will monitor how well you are responding to treatment. He or she will focus on the degree to which your symptoms improve and whether you have any drug-related side effects. This information will help determine whether a change or an adjustment in treatment is needed.
Your health care provider will keep track of how your disease progresses over time by listening to your comments about pain and ADLs and by repeating your physical examination, blood tests and X-rays. He or she will ask about how your disease affects your daily life. For example, symptoms can be severe even though findings on the examination, blood tests and X-rays are normal or only mildly abnormal. On the other hand, some people have only minimal or mild symptoms even though the examination and test results suggest severe disease. In such cases, you need a trusted and experienced health care provider determined to help you decide the best course of treatment.