C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) levels are "monitored" when a person is on Actemra (tocilizumab). When a person is on Actemra a doctor would expect a lower CRP and ESR. If your CRP and ESR aren't lower than there might be a problem.

My CRP and ESR were "negligible" when I was doing Actemra infusions every 4 weeks. When I didn't have an Actemra infusion for 7 weeks my ESR and CRP were elevated prior to my infusion at 7 weeks. My rheumatolgist used that as an indication that 7 weeks was too long of a time between my infusions. I denied any infection or any other reason to explain the jump in my ESR and CRP levels so it was a "significant change."

CRP and ESR are subject to interpretation based on the entire "clinical picture." Clinically, my rheumatologist said it "looked like" I wasn't doing as well after 7 weeks without an Actemra infusion.

I think the reliability of these acute phase reactants have to be evaluated considering a person is on Actemra. For example a person might present with symptoms of a serious infection. An infection shouldn't be ruled out based on a low CRP and ESR because they are on Actemra.

I don't think CRP and ESR are ever reliable measures of "disease activity" for people with PMR/GCA. Some people have active symptoms of PMR/GCA without having elevated ESR and CRP levels. Prednisone also has an effect on CRP and ESR levels.