Erythrocyte Sedimentation Rate and C-reactive Protein Measurements and Their Relevance in Clinical Medicine.

INTRODUCTION Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) are widely used laboratory markers of systemic inflammation. OBJECTIVE A thorough understanding of the similarities and differences between these two serological markers, including factors that affect measurements, is necessary for the proper utilization and interpretation of ESR and CRP. METHODS This review summarizes the current published literature (searched on MEDLINE through February 2016) surrounding the history and utilization of ESR and CRP, and examines factors that affect ESR and CRP measurements and discordance amongst these two inflammatory markers. RESULTS As ESR and CRP lack sensitivity or specificity, these tests should be used only in combination with clinical history and physical exam for diagnosis and monitoring of pathological conditions. The clinical application of these tests in diagnosis is best applied to conditions in which there is high or low clinical probability of disease. Importantly, discrepancies between ESR and CRP measurements commonly have been reported in both inpatient and outpatient settings and this problem may be particularly prevalent in chronic inflammatory diseases. Numerous physiological factors, including noninfectious conditions and resolution of inflammation can contribute to abnormally high ESR/low CRP readings or vice versa. CONCLUSIONS Although discordance may be encountered in certain settings, proper utilization of ESR and CRP measurements continues to play an important role in clinical management of many inflammatory and other conditions.