Diagnosing rheumatoid arthritis is often a challenge, even for experienced doctors.
There's no single test that can definitively diagnose rheumatoid arthritis (often called RA), or rule it out. Instead, doctors must rely on a comprehensive clinical assessment in which they consider the person's symptoms, other health conditions, data from blood work, and sometimes X-rays.
There's also a lot of variability in the way that people can first manifest their rheumatoid arthritis symptoms. For example, although it's common for people with rheumatoid arthritis to start off with symmetrical joint pain in both hands, some people start off with joint inflammation that moves from one joint to another over a period of months. Others may start off with persisting pain in just one joint, such as the knee.
In addition, symptoms of rheumatoid arthritis often overlap with those of other illnesses. In particular, symptoms similar to those of rheumatoid arthritis can be caused by viral illnesses, other autoimmune diseases, Lyme disease, other types of arthritis, or even a problem such as depression.
For these reasons, the diagnosis may require persistence and patience -- although in some cases the diagnosis of rheumatoid arthritis is straightforward.
Evaluation for possible rheumatoid arthritis often starts in the primary care office but is most thoroughly done by a rheumatologist, a specialist in joint and autoimmune diseases.
Here are the key features that doctors will be looking for, and why:
Physical signs of inflammation in the joints
Why: Inflamed joints are generally tender to the touch and hurt when moved. Rheumatoid arthritis often causes inflammation in the lining of three or more joints. It's less common but also possible to have rheumatoid arthritis symptoms in just one joint.
Morning stiffness lasting 30 minutes or more
Why: Many adults feel a bit stiff for the first five to ten minutes after getting up out of bed. Rheumatoid arthritis, on the other hand, can cause noticeable morning stiffness for an hour or more. Note that morning stiffness is also common in other inflammatory forms of arthritis, such as arthritis related to lupus.
Symptoms lasting for at least six weeks.
Why: Symptoms that have been going on for at least six weeks are more likely to be due to a chronic illness, such as rheumatoid arthritis, than to a viral infection or other shorter-term problem.
Laboratory signs of inflammation in the body
Why: If the history and physical exam suggest rheumatoid arthritis or another autoimmune disease, the doctor will probably order lab tests to look for inflammation. The most commonly ordered test is the erythrocyte sedimentation rate (ESR); a higher number indicates more inflammation in the body. Doctors may also order tests to measure blood levels of rheumatoid factor and anti-cyclic citrullinated peptide (anti-CCP) antibodies, which are often positive in people with rheumatoid arthritis. (However, note that these tests can be positive in healthy people as well.)
X-rays of the hands, feet, or other affected joints
Why: In more severe or advanced cases of rheumatoid arthritis, X-rays can show inflammation eroding into the bones. X-rays can also help track the progression of RA.
If you have a high rheumatoid factor level and classic joint pain, the diagnosis may be pretty straightforward. However, a person's symptoms and lab work often fall into a "gray zone," leaving the doctor thinking that this may or may not be rheumatoid arthritis. In this case, doctors may need to monitor symptoms over time in order to make a firm diagnosis.
If you or your loved one have been told you that "may" have rheumatoid arthritis, be sure the doctor explains what other diagnoses are being considered, and what the plan is for following up on the symptoms. A referral to a rheumatologist can also be helpful.