Briefly, What is Rheumatoid Arthritis?
Rheumatoid arthritis (RA) is an inflammatory disease that affects the joints of the body. RA symptoms can be very mild (for example, a mild tingling in the knees is felt) or very severe and debilitating (for example, pain in the knees is so hurtful that the suffer cannot walk without assistance).
For a more detailed description of rheumatoid arthritis, please read "Rheumatoid Arthritis Causes: Risk Factors that Contribute to RA."
How is Rheumatoid Arthritis Diagnosed? What Specific Tests Are Used?
Diagnosing rheumatoid arthritis when the disease is in its early stages can be quite challenging. Usually, clinicians take a two-pronged diagnostic approach: (1) they rule out other diseases as being the culprit; and (2) they perform one or more of the multiple diagnostic laboratory tests that are useful in identifying the presence of RA. Once the clinician eliminates other diseases as possibilities, and it appears more than likely that RA may be the cause of the patient’s symptoms, specific laboratory tests that are available to the clinician include:
- Test for Rheumatoid Factor. Rheumatoid factor is an antibody that is produced in most people who have RA, especially as RA reaches more advanced stages. In this test, blood is drawn from the patient and a sample of the blood is analyzed for the presence and level of the rheumatoid factor antibody in the sample. A low level of this factor in the blood is merely suggestive that the patient has RA, whereas a high level is essentially dispositive that RA is the culprit disease. Therefore, one problem with the rheumatoid factor test is that it is actually possible that a person can generate rheumatoid factor in detectable levels but be free of the disease. Another problem with the rheumatoid factor test is that not all people who have RA generate a detectable amount of the rheumatoid factor. These people, therefore, produce negative test results (which are misleading because these individuals, in fact, have RA). For this reason, it cannot be assumed that a person who produces a negative test result is actually free of the disease.
- Test for antibodies to CCP. CCP (which is an acronym for "cyclic citrullinated peptide") is generated by the body whenever inflammation persists. The presence of specific antibodies that the body produces in response to this CCP is therefore, indicative that the patient has RA, which, again, is an inflammatory disease. One significant problem to this test is that people can suffer from RA for many years before antibodies to CCP are generated in the body. Therefore, failure to detect these antibodies does not necessarily confirm that the patient is free of RA. (Due to the various limitations of the test for rheumatoid factor and the test for antibodies to CCP, both tests, as opposed to only one or the other, are typically performed in conjunction such as to optimize the evidence that a patient either has or does not have RA.)
- X-ray examinations. In late stages of rheumatoid arthritis, joint damage usually is detectable simply by visualizing the joints by using x-ray analysis. Observation of such joint damage is highly suggestive that the patient has RA. A significant drawback to using x-ray analysis is that it is only useful when the patient has an advanced form of RA, and therefore, it cannot be used reliably for diagnosing patients who have less advanced or early-stage RA, which is the case of most patients when they first seek diagnosis.
In addition to the aforementioned tests, other means that are sometimes used to help diagnose RA in a patient include white blood cell counts, the blood test for anemia, and two other tests for the presence of inflammation: (1) the erythrocyte sedimentation rate test; and (2) the C-reactive protein test. While these tests are helpful, the most commonly employed tests, however, are the test for rheumatoid factor and the test for antibodies to CCP.
If you believe that you may have RA, please consult your family physician. This article is meant only to provide basic background information regarding the various tests that are used in diagnosing rheumatoid arthritis in a patient. It is not meant to replace the advice or medical opinion of your doctor.
National Institutes of Health, Handout on Health: Rheumatoid Arthritis (https://www.niams.nih.gov/health_info/rheumatic_disease/#ra_9)
T. Pincus and T. Sokka, Laboratory tests to assess patients with rheumatoid arthritis: advantages and limitations, Rheumatoid Disease Clinics of North America, 35:731-734 (2009).