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How can the diagnosis of rheumatoid arthritis be confirmed?

Q: I am a 51 years old male. After my medical check-up, the doctor told me that the level of antinuclear antibody in my body is very high. For a normal person it is 80 but my value is 2560. I did do a blood test for rheumatoid arthritis last year but it was negative so I am a bit confused about the sudden increase in that antibody levels. Do you have any explanation about this? My doctor said that it can be hereditary. My parents have never suffered from this disease though my mother’s sister though has rheumatoid arthritis. How can I be sure that I have rheumatoid arthritis?

A:Anti-nuclear antibodies (ANA) are an unusual type of gamma-globulins found in patients with certain autoimmune diseases. ANAs are directed against certain components found in the nucleus of a cell in the body. They are found in patients whose immune system is predisposed to cause inflammation against their own body tissues (autoimmune diseases).

These antibodies can be detected by several techniques like enzyme-linked immunosorbent assay (ELISA), Indirect immunofluorescence (IF), Counter immunoelectrophoresis (CIE) and Immunoblotting assay (IB). The sensitivity and specificity of various techniques varies as does the format of their reporting. The results are usually reported as a titer with a particular type of immunofluroscence pattern (when positive). Low-level titers are considered negative, while increased titers, such as 1:320, are positive and indicate an increased concentration of the antibodies.

A positive ANA result means a higher than normal concentration of these antibodies. This may be due to a disease called lupus erythematosus or some other autoimmune disease like Sjogren’s syndrome, scleroderma, Raynaud’s disease, rheumatoid arthritis, dermatomyositis, mixed connective tissue disease, and other autoimmune conditions. It may also be positive due to some drugs and infections. Finally, ANA test results can be positive in people without any known autoimmune disease (false positive) which is simply a fact that you have a higher than normal concentration of these autoantibodies that may not have any impact on your health. The chances of a false positive ANA result increases as people get older. Most positive ANA results don't have significance, so doctors usually reassure their patients but remain vigilant for development of signs and symptoms that might suggest an autoimmune disease. Also, ANA may become positive before signs and symptoms of an autoimmune disease develop, so it may take a while to interpret a positive ANA result in an individual who has no symptoms. Even patients suffering from lupus have widely varying results can with one being in remission at a certain ANA titer while another may have severe symptoms at the same titer. Interpreting the results is done in conjunction with symptoms and further specific testing over a period of time in order to make a definitive diagnosis.

The random chance of a false positive in normal individuals is considerably greater than a true positive, unless the doctor selects only individuals with a reasonably high possibility of having the disease before testing. Therefore, careful selection of patients to be tested is of great importance as improper use of ANA testing can lead to misinformation, incorrect diagnoses and a waste of money. This is because, even with the newest tests, about 5% (1 out of 20) of normal individuals will give a weakly positive result and ANA should never be ordered as a routine screening test. A positive ANA result in a patient with no or minimal features of SLE can be misleading or worse because it may cause the doctor to order unnecessary tests.


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