The Rheumatoid Factor (RF) test is a blood test used to detect the presence of rheumatoid factor, an antibody that is often associated with autoimmune diseases, particularly rheumatoid arthritis (RA). Rheumatoid factor is produced by the immune system and can attack healthy tissues, leading to inflammation and joint damage. The RF test is not solely diagnostic for rheumatoid arthritis, as it can also be present in other conditions such as Sjögren's syndrome, lupus, and even in some healthy individuals, particularly older adults. Typically, the RF test is ordered when a patient presents with symptoms such as joint pain, swelling, and stiffness, especially if these symptoms persist for six weeks or longer. A positive RF test indicates the presence of rheumatoid factor but does not confirm a diagnosis of rheumatoid arthritis on its own. Instead, it is used in conjunction with other clinical evaluations, including physical examinations and imaging studies, to provide a comprehensive assessment of the patient's condition. The test results are reported as a titer, with higher levels of RF often correlating with more severe disease. However, it is important to note that not all patients with rheumatoid arthritis will test positive for RF, leading to the classification of seronegative rheumatoid arthritis. Overall, the RF test is a valuable tool in the diagnostic process, helping healthcare providers to identify autoimmune disorders and tailor appropriate treatment plans for affected individuals.