The laboratory identification of serum rheumatoid factor in the dog.

A modified Rose-Waaler test with sheep red blood cells coated with canine IgG was found satisfactory for detecting rheumatoid (antiglobulin) factor (RF) in dog serum. Low titres of RF were found in some normal dogs. Most dogs with rheumatoid arthritis were positive for RF at titres of 1 in 40 or greater. A small proportion of dogs with diseases other than polyarthritis were also positive for RF. A commercial slide agglutination test used for detecting human RF was unsatisfactory for the dog, giving false positive and negative reactions. A latex tube agglutination test with latex particles coated with dog IgG was developed but non-specific agglutination was a constant technical problem.