ESR and CRP in Rheumatoid Arthritis Flares

Relationship Between Inflammatory Markers and RA Disease Activity

ESR and CRP are commonly used acute phase reactants in the assessment of rheumatoid arthritis disease activity and should be performed at baseline and repeated when clinically relevant, as recommended by the European League Against Rheumatism 1, 2.
Elevated CRP is particularly useful in predicting RA when levels are higher, with a diagnostic value for the development of RA 2.
In established RA, ESR and CRP are included in composite disease activity measures such as the Disease Activity Score 28 (DAS28) and Simplified Disease Activity Index (SDAI), reflecting their importance in assessing disease activity, according to the American College of Rheumatology 3, 4.

The inclusion of acute-phase reactants in disease activity measures introduces complexity, as ESR contributes a sizeable portion (15%) of the information in the DAS28-ESR, as noted by the American College of Rheumatology 4.
Remission may be underestimated in high ESR states with few active joints, while in low ESR states, remission criteria may be met despite a significant number of swollen joints, according to the American College of Rheumatology 4.

Newer biologic agents targeting specific inflammatory cytokines may disproportionately affect ESR or CRP levels, potentially deflating composite disease activity scores, as reported by the European League Against Rheumatism 4.