Which of the following is an indicator of rheumatoid arthritis?

A key indicator of rheumatoid arthritis is symmetrical joint swelling. This condition is characterized by inflammation that affects the same joints on both sides of the body, which is a hallmark feature of rheumatoid arthritis. This symmetrical pattern helps distinguish it from other types of arthritis, such as osteoarthritis, which often affects one joint at a time or predominantly one side of the body. The identification of symmetrical swelling is critical in the diagnosis as it suggests an autoimmune process, which is central to rheumatoid arthritis.

In contrast, joint pain that worsens at night, typically seen in conditions like osteoarthritis, does not characterize rheumatoid arthritis. Patients with rheumatoid arthritis often experience stiffness and discomfort that can improve throughout the day. Age greater than 70 years is not a specific indicator of rheumatoid arthritis, as this condition can occur at any age and is more strongly correlated with genetic and environmental factors than age alone. Finally, swelling in only affected joints is more indicative of localized conditions rather than the systemic and symmetrical nature of rheumatoid arthritis. Hence, symmetrical joint swelling is the definitive indicator of this autoimmune disease.