The standard name for “anti-O” is anti-strep O factor, and the standard value is 0-200 units. Exceeding the standard indicates that the body has or has had a strep infection, and this pathogen causes an abnormality in immunity, which is manifested as an elevated ASO. If this immune response occurs in the joints, it causes redness, swelling, and pain in the joints, which is commonly referred to as rheumatoid arthritis. Although elevated anti-strep O factor is a distinctive feature of rheumatoid arthritis, high “anti-O” does not necessarily indicate rheumatoid arthritis, because all diseases caused by streptococcal infections can cause elevated anti-strep O factor, such as upper whistle infections, acute rheumatic fever, and so on. Therefore, the diagnosis must be combined with the patient’s joint symptoms and other laboratory indicators. Rheumatoid arthritis causes pain in the joints of patients and is present in most joints. The name of this disease is similar to “rheumatoid arthritis,” but the damage caused is very different, as are the medications and the prognosis for the disease. Rheumatoid arthritis usually involves pain in small joints, such as the interphalangeal joints and wrist joints, often symmetrically, with morning stiffness, or in large joints, but the pain and swelling are usually fixed. In contrast, the main symptom of rheumatoid arthritis is pain in the large joints of the body, such as the knee, hip, elbow, etc. This pain is wandering, meaning that the location of the pain may change frequently and there is no morning stiffness. In addition, laboratory tests (i.e., blood tests) for antinuclear antibodies, rheumatoid factor, and anti-CCP can help rule out the possibility of rheumatoid arthritis. If rheumatoid arthritis is diagnosed, the application of penicillin and aspirin can be effective treatment, and the joints can generally recover as before after cure; whereas rheumatoid arthritis requires DMRDS treatment, which is not curable at this time. Our treatment goal is to maximize the protection of the patient’s joint function, because the disease, if not well controlled, can deform the joints and cause permanent functional damage. Rheumatoid arthritis is and can be one of the manifestations of acute rheumatic fever. This pathogenic bacteria can cause damage to heart function and develop rheumatic heart disease, so patients also need to have a heart ultrasound. Streptococcal infection can also lead to kidney damage and glomerulonephritis, so patients with rheumatoid arthritis should also have their urine routine checked during the visit to observe kidney functions such as urine protein and laboratory tests for blood creatinine.