Inflammatory Markers

ESR and CRP are lab tests that rheumatologists often order.

I though that these numbers were meaningful.  It turns out I was wrong: 

Whatever the value of knowing normal values for ESR and CRP in the general population, the values have little meaning in patients with RA who are not representative of the general population.

I thought that these labs gave some indication of disease activity.  It turns out I was wrong:

there is no clear rational cutoff for activity (or for normality) of ESR/CRP in RA.  Many people with active RA have inactive values of ESR/CRP and many with inactive RA have active values.

These quotes are from The Many Myths of Erythrocyte Sedimentation Rate and C-Reactive Protein, in Journal of Rheumatology.  Very interesting article.