: Rheumatoid Factor Titer, Serum or Plasma by Agglutination

: What This Test Measures

: Rheumatoid factor (RF) is an antibody that can attack a person's own tissues, most often the joints. The titer reports how much of this antibody is present in your blood, expressed as the highest dilution at which it can still be detected. A higher titer generally means more antibody is present.

: How the Sample Is Collected

: A small blood sample is drawn from a vein, usually in your arm, and processed to separate serum or plasma for testing. The agglutination method detects RF by observing how the sample reacts with treated particles. No special preparation is usually needed, but follow any instructions from your care team.

: Why Your Clinician May Order It

: This test may be ordered when you have joint pain, swelling, or stiffness that could suggest rheumatoid arthritis or another autoimmune condition. It is often interpreted together with your symptoms, a physical exam, and other blood tests such as inflammatory markers and other autoantibodies.

: Understanding the Result

: Results are reported as a titer rather than a simple positive or negative. Higher titers are more often seen in rheumatoid arthritis, but RF can also be present in other conditions and even in some healthy people, especially older adults. Your clinician will interpret the titer alongside your overall picture.