The number and size of joints that are swollen. The doctor counts how many large joints (shoulders, elbows, hips, knees, ankles) and how many small joints (the small joints in the wrists, hands, and feet) are swollen. You may hear these criteria called “joint involvement.”

You get a score from 0 to 5.

Blood tests. The part of the blood called “serum” is evaluated to look for rheumatoid factor (RF) and anti-cyclic citrullinated peptide antibodies (anti-CCP or ACPA). These are usually higher than normal in people who have rheumatoid arthritis. You may hear these criteria called “serology.”

You get a score from 0 to 3.

Additional blood tests. The blood is also tested for C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR or sed rate). These tests show whether there is inflammation in the body. You may hear these criteria called “acute-phase reactants.”

You get a score of 0 or 1.

How long symptoms have lasted. The doctor notes whether symptoms have lasted less than 6 weeks, or 6 or more weeks. You may hear these criteria called “duration of symptoms.”

You get a score of 0 or 1.