Rheumatoid factor (RF)

What this test is

Rheumatoid factor, or RF, is a blood test. It helps check for rheumatoid arthritis. This is a disease where the immune system attacks the joints. This test works best when you have real joint symptoms. That means ongoing swelling in a pattern typical for this disease. On its own, RF is not very precise. Many people without rheumatoid arthritis test positive too. This includes some healthy older adults. A newer test called anti-CCP is more accurate. In Ontario, only specialists can order it, not family doctors or NDs. If you have joint pain but no swelling, RF is usually not the next step. If your joints show active inflammation, this test is worth doing. Catching this disease early really does help.