Lately we have been discussing usefulness and misuse of the rheumatoid factor (RF). Patients without RF fear that their complaints are’nt taken earnestly as for their GP no RF means no rheumatic disease. Rheumatologists see lots of patients with osteoarthritis plus RF, who don’t have a rheumatic disease; occasionally patients are referred without any joint complaints ore other hints to a rheumatic disease safe for the RF, which the GP had tested for obscure reasons.
The rheumatoid factor (RF) is an autoantibody that is relevant historically in rheumatoid arthritis, as it defined the disease. But with all autoimmune findings, scrutiny is necessary. Negative results don’t rule out arthritis, not even rheumatoid arthritis. A positive result, however, doesn’t equal having rheumatoid arthritis as the result may be due to other causes. RF is still part of the combined EULAR and ACR classification criteria of rheumatoid arthritis though another biomarker ACPA (Anti Citrullinated Peptide Antibody) has made it’s way into these criteria. Let’s have a closer look at these criteria. The criteria are applied by scoring for joint involvement, serology, duration of synovitis, and acute phase reactants (ESR and CRP). The criteria might be positive for rheumatoid arthritis without RF nor ACPA. On the other hand most people with rheumatoid arthritis test positive for RF. It is much like with ankylosing spondylitis, where most of the patients test positive for HLA B27, but not all – positive for HLA B27 doesn’t mean having the disease, but a negative result doesn’t rule ankylosing spondylitis out (sounds familiar?!).
Which dieases also go along with an elevated RF? Quite a lot. In the field of rheumatic diseases we have: adult onset Still's disease (AOSD), dermatomyositis Sarcoidosis, scleroderma, Sjogren’s syndrome, systemic lupus erythematosus. Other conditions include infectious diseases (viral and bacterial infections, tuberculosis, parasites), leukemia and other cancers, as well as chrinc lung and chronic liver disease. This isn’t an exhausting list.
To go deeper into this look up rheumatoid factor and rheumatoid arthritis on Wikipedia or have a look at my colleague and friend’s, Dr. Shashank Akerker’s page at: http://www.arthritissupportboard.com/rheumatoid_factor.aspx and http://www.arthritissupportboard.com/Rheumatoid_Arthritis_Diagnosis.aspx.
We have to talk about a tedious topic: classification after the International Statistical Classification of Diseases and related Health Problems: ICD-10. The positive thing about this classification is the world wide distribution. You can compare statistical data, that’s what it has been made for. As we use it to generate DRGs (Diagnose Related Groups) it has become daily practise to put complex diagnosis into a couple of letters and numbers. Rheumatoid factor positive rheumatoid arthritis is classified M05.80, without RF you classify the disease as M6.00. Rheumatoid nodules are classified M6.3x; I haven’t seen one patient without RF having rheumatoid arthritis; has anyone else? This classification reflects an older state of knowledge. It’s arbitrary and idiosyncratic. At this point it seems that RF is tested to distinguish between RF+ and RF- rheumatoid arthritis. As there might be some small differences, I’d like to let it stand like this. But why doe stress RF so much, as we aren’t differentiating between RA of large joints, of small joints, only wrists, only fingers, only feet, with and without cervical spine involvement, with and without involvement of inner organs, with and without other auto antibodies?
Mrs. R.H. is 67 years old and RA was diagnosed in the early 90ies. I’m treating her since the mid-90ies. Until 2006 fluctuations of RF also meant new flares. 2001-2002 we tried an immune absorption therapy; you can see a drop and then a steady state in 2003-2004. The therapy had to be escalated during the low phase. RF was rising and she went into remission (TNF-alpha inhibitor). With Mrs. R.H. any fluctuations of RF have no meaning concerning disease activity
Rheumatoid factor is the oldest antibody we use and we still don’t know its use.
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