Depends which blood tests you mean. If you're referring to inflammatory markers, ie ESR or CRP, then yes hydroxy could alter things. It is a disease modifying drug, so if it is being effective then it will bring down your inflammatory markers. But if you're having an MRI done that should show up whether there's disease activity or damage.
Those are different blood tests, for the rheumatoid factor and the anti-CCP antibodies. A lot of people are negative for these but still have RA. Normally the drugs don't affect these a lot, and if anything make them drop.
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