The diagnostic criteria for rheumatoid arthritis include, first, the presence of swelling and pain in multiple joints, especially characterized and significant in the smaller joints. Second, serological tests show elevated levels of antibodies, commonly rheumatoid factor and anti-CCP antibodies. If both are elevated, it is most meaningful. Third, the duration of joint swelling and pain should be more than six weeks. Fourth, we must also check some inflammatory markers for joints, such as elevated erythrocyte sedimentation rate and C-reactive protein. If these markers are elevated, and the patient has swelling and pain in multiple joints, then we can consider a diagnosis of rheumatoid arthritis.