Diagnosing Rheumatoid arthritis

Last week I saw a 50 year old lady from the UK and she had a 6 week history of pain and swelling in her right index finger and also toes.  When I examined her I found swelling and tenderness of 1 joint in the right 2nd finger (PIP) and 2 joints of the toes (MTP).  The signs were so minimal and even though she had a high titer positive Rheumatoid factor I did not believe she had full blown rheumatoid arthritis.  I repeated the rheumatoid factor which came back very high and she also had a positive test for anti- CCP.  Although she had minimal symtoms she was classified as early rheumatoid arthritis and we started her on methotrexate .  In this case the positive tests helped the diagnosis. 

Another patients I saw today had a 6 month history of swelling and tenderness of fingers and toes.  Many joints were involved but she had normal ESR CRP Rheumatoid factor and anti-CCP.  She was told she did not have rheumatoid arthritis.  I told her she has definite rheumatoid arthritis and she was started on treatment.  In this case the clinical signs are more important than the blood tests.

Classification criteria for RA (score-based algorithm: add score of categories A–D; a score of ≥6/10 is needed for classification of a patient as having definite RA)‡
A. Joint involvement §
1 large joint¶	0
2-10 large joints	1
1-3 small joints (with or without involvement of large joints)#	2
4-10 small joints (with or without involvement of large joints)	3
>10 joints (at least 1 small joint)**	5
B. Serology (at least 1 test result is needed for classification)††
Negative RF and negative ACPA	0
Low-positive RF or low-positive ACPA	2
High-positive RF or high-positive ACPA	3
C. Acute-phase reactants (at least 1 test result is needed for classification)‡‡
Normal CRP and normal ESR	0
Abnormal CRP or abnormal ESR	1
D. Duration of symptoms§§
<6 weeks	0
≥6 weeks	1