When RA is clinically suspected,testing for the presence of rheumatoid factor (RF, a specific antibody). A negative RF does not rule out RA; rather, the arthritis is called seronegative.
RF is also seen in other illnesses, for example Sjögren's syndrome, and in approximately 10% of the healthy population, therefore the test is not very specific.
Because of this low specificity, a new serological test has been developed, which tests for the presence of so called anti-citrullinated protein antibodies (ACPAs). Like RF, this test is positive in only a proportion (67%) of all RA cases, but is rarely positive if RA is not present, giving it a specificity of around 95%.
As with RF, there is evidence for ACPAs being present in many cases even before onset of clinical disease.Currently, the most common test for ACPAs is the anti-CCP (cyclic citrullinated peptide) test.
Also, several other blood tests are usually done to allow for other causes of arthritis, such as lupus erythematosus. The erythrocyte sedimentation rate (ESR), C-reactive protein, full blood count, renal function, liver enzymes and other immunological tests (e.g. antinuclear antibody/ANA) are all performed at this stage. Elevated ferritin levels can reveal hemochromatosis, a mimic RA, or be a sign of Still's disease, a seronegative, usually juvenile, variant of rheumatoid.
Diagnostic criteria
The American College of Rheumatology has defined (1987) the following criteria for the classification of rheumatoid arthritis:
Morning stiffness of >1 hour most mornings for at least 6 weeks.
Arthritis and soft-tissue swelling of >3 of 14 joints/joint groups, present for at least 6 weeks
Arthritis of hand joints, present for at least 6 weeks
Symmetric arthritis, present for at least 6 weeks
Subcutaneous nodules in specific places
Rheumatoid factor at a level above the 95th percentile
Radiological changes suggestive of joint erosion
At least four criteria have to be met for classification as RA.
I think you have some fair idea about RA diagnosis and also about RF.Take care and come back to us with further queries.
sorry I forgot to say when looking up the symptoms, I have no nodules, morning stiffness, or there doesn't appear to be any swelling.
i also had the same RF test done two weeks prior at a different hospital and the doctors said that this was a sensitive test and wanted to repeat it. the first time I had no infection the 2nd time I have an infected ingrown toe nail, that I had only been on antibiotics for 2 days before having the tests, could this ahve affected the results any?