Rheumatoid factor (RF)
| Category | Immunology |
|---|---|
| Test background |
RF is an autoantibody directed against the Fc portion of immunoglobulin G (IgG). The most clinically measured and useful class of rheumatoid factor is IgM, which is found in 50-90 % of patients with rheumatoid arthritis. It is also seen in Sjogren's syndrome (70-80 %) and to a lesser degree in other rheumatological conditions, such as SLE, systemic sclerosis, juvenile rheumatoid arthritis and polymyositis. It is seen in 5-10 % of healthy adults and also in those with an intercurrent infection (up to 50 %). |
| Clinical Indications |
Arthralgia, bone pain Differential diagnosis of arthritis |
| Reference range | <20 IU/ml |
| Sample & container required | SST (gold top) |
| Sample volume | 5-10 mL (1 mL serum) |
| Turnaround time | 3 days |
| Notes | The laboratory is currently unaccredited for this test due to a change in platform. |