ESR and CRP in Rheumatoid Arthritis Flares
Yes, erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) are typically elevated during rheumatoid arthritis flares, but they can be discordant in a significant number of patients.
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 1.
Both markers show some diagnostic value for the development of RA, with elevated CRP being particularly useful in predicting RA when levels are higher 1.
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 1.
Discordance Between ESR/CRP and Clinical Disease Activity
Despite their utility, studies show that approximately 58% of patients with active RA (based on Clinical Disease Activity Index) may have neither elevated ESR nor CRP; only 16% have both elevated, and 26% have either ESR or CRP elevated 2.
The correlation between these inflammatory markers and clinical measures of disease activity (joint counts, patient/physician assessments) is often weak 3.
ESR and CRP have a modest positive correlation with each other across rheumatic diseases (correlation coefficient 0.59-0.69) 4, 5.
Clinical Implications
When evaluating a potential RA flare, it's recommended to obtain both ESR and CRP at the initial assessment since either one may be normal despite active disease 2.
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 1.
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 1.
Special Considerations
Newer biologic agents targeting specific inflammatory cytokines may disproportionately affect ESR or CRP levels, potentially deflating composite disease activity scores 1.
In distinguishing between infection and flare in rheumatic diseases, the ratio of ESR:CRP may provide additional diagnostic value, with higher ratios associated with disease flare rather than infection 6.
Age can affect inflammatory marker levels, with patients older than 40 years typically having higher ESR and CRP values 5.
In summary, while ESR and CRP are valuable tools in assessing RA disease activity and are typically elevated during flares, clinicians should be aware that normal values do not exclude active disease, and clinical assessment remains paramount in evaluating disease activity.