the tests for RA may be negative even in RA.
There is no test which is the diagnostic test for rheumatoid arthritis
. It is a clinical diagnosis.
diagnoses it by examining your joints, taking your history and offcourse doing a few tests.
The tests like rheumatoid factor
and anti CCP do help in confirming the diagnosis, however they may be negative in 10-15% of patients.
So even in osteoarthritis
your hands may look like that of rheumatoid, sine OA also causes swelling and enlargement of joints. So the treating doctor is the best person to decide what exactly you are suffering from.
Hope this clarifies your doubt. Let me know if you need clarifications.