There is no one test that is conclusive for a diagnosis of rheumatoid arthritis (RA). RA is generally diagnosed through a combination of a physical examination, family history, blood tests, and imaging scans. RA is usually diagnosed by a rheumatologist, or specialist in musculoskeletal and autoimmune diseases.
How is rheumatoid arthritis diagnosed?
RA – especially when the symptoms are mild – is often misdiagnosed. RA can resemble other conditions including lupus, spondylitis, Sjögren’s syndrome, gout, and osteoarthritis. The doctor carefully considers many different test results before concluding that RA is the correct diagnosis or ruling it out.
Physical exam and family history
Typically, the rheumatologist will start by examining your joints to check for swelling, nodules, redness, warmth, and symmetry – whether symptoms appear on the same joints on both sides of the body. Mobility limitations and associated pain will also be assessed. You may also be asked about family medical history of RA or other autoimmune diseases, which may increase your risk factors for developing RA.
Diagnosis may also involve blood tests or imaging procedures such as X-rays, ultrasound, or magnetic resonance imaging (MRI) scans. Scans allow the doctor to check for joint damage during diagnosis, and later measure how the disease progresses over time.
Although no lab test is conclusive for RA, they provide important clues that make an RA diagnosis seem more likely or help rule it out.
Blood tests look for specific proteins that act as biomarkers for RA and other inflammatory conditions. One biomarker, anti-cyclic citrullinated peptide (anti-CCP), is found in around 60 to 70 percent of people with RA. Anti-CCPs can appear in blood five or even 10 years before RA symptoms appear. Bloodwork may also look for rheumatoid factor (RF), although RF can also be found in people with conditions other than RA. The presence of anti-CCP and RF indicate an autoimmune reaction.
Furthermore, if you go on to be diagnosed with RA, whether or not you test positive for RF or anti-CCP provides criteria for being typed as seropositive (having RF or anti-CCP in the blood) or seronegative (not having RF or anti-CCP in the blood). Knowing your type of RA helps your doctor better predict your disease course and recommend the medication most likely to be effective in managing your RA.
Blood tests can also check overall levels of inflammation by examining erythrocyte sedimentation rate (ESR, or sed rate) and C-reactive protein (CRP). At elevated levels, both ESR and CRP are considered signs of inflammation and can indicate RA or another inflammatory condition.
Similarly, anemia, or low red blood cell count, is another lab result often seen in people with RA.
At what age does rheumatoid arthritis start to develop?
When RA develops before the age of 17, it is referred to as juvenile arthritis. Non-juvenile rheumatoid arthritis typically develops between ages 30 and 60. Read more about different types of RA.