C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) are common measures of systemic inflammation. Our goal was to identify clinical factors associated with CRP/ESR discordance.
We identified patients with ESR and CRP results at our academic hospital over six months. We matched individuals with discordant results (one measure in highest tertile, other in lowest), by age and sex to those with non-discordant results, and reviewed medical records for laboratory and clinical factors. We employed analysis of variance (ANOVA) and Chi squared tests to compare these variables in discordant and non-discordant subjects. We used conditional logistic regression to estimate the relative risk of CRP/ESR discordance associated with each variable.
2,069 patients had CRP and ESR measured on the same day; 87 had discordant results, 55 (2.6%) with elevated ESR/low CRP, 32 (1.5%) with elevated CRP/ low ESR. Underlying infection was associated with > 14 fold risk of elevated ESR/low CRP discordance (p < 0.001). Renal insufficiency was associated with increased risk of elevated ESR/low CRP discordance, (p = 0.003). RA patients were slightly less likely to have elevated ESR/low CRP, (p = 0.008, NS after Bonferroni correction). Low serum albumin was associated with both kinds discordance.
Infection, renal insufficiency, and low albumin were associated with having elevated ESR/low CRP; low albumin predicted elevated CRP/low ESR and elevated ESR/low CRP discordance. RA patients were less likely to have elevated ESR/depressed CRP. ESR as a measure inflammation in systemic rheumatic disease may be limited in settings of infection, renal insufficiency, and low albumin.