If you've developed antibodies, from my experience, Remicade starts decreasing in the effectiveness. So, an infusion will not last as long. The final, worst, sign is to have a reaction during an infusion. Remicade never lasted the full 8 weeks for me, but by the end I needed it every 4 weeks or I'd flare again.
Yes, there is a blood test by Prometheus Labs that will test for antibodies. They are expensive and not always covered by insurance, so you might want to look into that part first just to be aware of what you're asking for.
--39 year old female, dx as UC in '04 (1st symptoms in '03), switched to Crohn's in '05
--1 fistula, crohn's colitis, limited to large intestine
--rejected (reaction/didn't work): Asacol, AZA, 6-MP, MTX, Remicade, Humira, prednisone
--stuck on methylprednisolone
--tried Prochymal in Phase III study (can't wait til it's approved!)
--waiting to start Tysabri
--single mom to 10-year-old girl