Rheumatoid factor

Rheumatoid factor

Species: Dogs

Specimen: Serum

Container: Plain (red top) or gel tube

Collection protocol: Venepuncture

Special handling/shipping requirements: Standard

General information about the disease:

Canine rheumatoid-like polyarthritis is a non-infectious, erosive polyarthritis. Affected dogs have episodes of anorexia, depression and fever with generalised or shifting lameness associated with swelling around the joints. Many of the dogs affected are of the small and toy breeds, with a significant number being Shetland sheepdogs.

Rheumatoid factors are IgM and IgG antibodies. They react with an antigen, which is altered endogenous IgG protein to form immune complexes in the joints. It is not clear why the IgG protein changes to become recognised as foreign by the immune system. Serologic testing for RF is expected to be positive in up to 70% of dogs with this disease so a negative result does not rule out the disease. False positive results can also occur in dogs with other systemic inflammatory disease so clinical correlation is required.

General information about when this test is indicated: In dogs with clinical signs suggestive of immune mediated arthritis

Comparison with other related tests: It is important to rule out bacterial arthritis, bacterial endocarditis and systemic lupus erythematosus before considering rheumatoid arthritis.