The Rheumatoid Factor (RF) test is a blood test used to detect the presence of antibodies in the blood that target a protein called Rheumatoid Factor. Rheumatoid Factor is an antibody that is commonly found in the blood of individuals with Rheumatoid Arthritis (RA), an autoimmune disease that causes inflammation and pain in the joints. The RF test is used as a diagnostic tool to help confirm a diagnosis of RA or other autoimmune diseases that may have similar symptoms. However, it is important to note that a positive RF test result does not necessarily mean that a person has RA, as some individuals may have elevated RF levels without experiencing any symptoms of the disease. Therefore, the RF test is often used in combination with other diagnostic tests and assessments to determine the presence and severity of RA.