Rheumatoid arthritis (RA) affects approximately 1 in 100 people in the United States. Women are afflicted 2 to 3 three times more often than men, with disease onset most often occurring between the ages of 35 and 50 years.
RA is an autoimmune disease that damages peripheral joints—particularly those of the hands and feet—but any joint can be involved. The condition is often accompanied by systemic signs and symptoms that include fatigue, morning stiffness, weakness, poor appetite, low-grade fever, subcutaneous nodules, vasculitis, pericardial or pleural effusions, myocarditis, pulmonary fibrosis, Sjögren’s syndrome, or neuropathy.
The Common Approach to Diagnosing Rheumatoid Arthritis
- While most physicians who suspect RA in a patient will order a battery of blood tests to confirm the diagnosis, too often this condition is erroneously ruled out when one or more of those tests is negative.
- The serologic marker that seems to carry an inordinate amount of weight in the diagnosis of RA is rheumatoid factor (RF). Rheumatoid factors are a class of auto-antibodies that participate in the inflammatory destruction of joint tissue in patients with RA. High levels of RF often signify a more rapid progression of the disease and a poorer long-term prognosis.
- Unfortunately, RF is only present in about 70% of RA patients early in the course of the disease. Therefore, strict reliance on a positive RF for diagnosis will miss at least 30% of cases. Additionally, RF is present in approximately 3% of the normal population, and it can also be present in patients with other diseases. Thus, on its own, RF is not a particularly sensitive or specific marker for rheumatoid arthritis.
- The diagnosis of RA is mainly clinical, which implies that a doctor must obtain a complete history and perform more than a perfunctory physical examination.
The Clinical Diagnosis of Rheumatoid Arthritis
The American College of Rheumatology has developed a series of criteria that should be used to classify patients who may have RA. Any four of these criteria must be present to make a diagnosis:
- Morning stiffness that lasts an hour or more*
- Arthritis in three or more joints*
- Arthritis of hand joints (wrists, metacarpophalangeal, or proximal interphalangeal joints)*
- Symmetric arthritis*
- Rheumatoid nodules (subcutaneous nodules that usually develop at sites of pressure or chronic irritation [e.g., the backs of the forearms])
- Positive rheumatoid factor
- Unequivocal x-ray changes consistent with RA (typical erosions and bony decalcification)
(*Must be present for at least six weeks)
In an era when physicians are pressed to see as many patients in as little time as possible, RA is one condition that can be overlooked in its early stages. This can prove particularly detrimental, since RA often progresses most rapidly during its first year, and the disease often responds to disease-modifying anti-rheumatic drugs (DMARDs) that slow the progress of the condition and preserve long-term function.
Patients who believe they may be developing RA—particularly those with a family history of this illness—should be cognizant of RA’s signs and symptoms, and they should press their physicians for more than just a blood test.
(From The Merck Manual, 18th Edition 2006:283-9 and Rindfleisch J, Muller D. Diagnosis and management of rheumatoid arthritis. Am Fam Phys 2005;72(6):1049-50)
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