CRP versus Erythrocyte sedimentation rate (ESR) |
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Increased erythrocyte sedimentation rate (ESR) is a nonspecific inflammation marker discovered much
before CRP and still in frequent use as an indicator of systemic chronic infections or malignancies.
ESR is primarily based on changes in the aggregation (roulette formation or piling) tendency of red
blood cells. ESR depends on the concentration of positively charged serum proteins such as fibrinogen
and immunoglobulins, with increased concentrations neutralising the net negative charge (zeta potential)
of red blood cells.
CRP assay could - and should - replace ESR assays in many diagnostic recommendations, as CRP reflects
changes in inflammatory activity faster and, being an internationally standardised immunometric assay,
provides more reliable results.
ESR is a complex phenomenon depending not only on the inflammatory condition but also on red cell density,
plasma viscosity, red cell morphology and haemoglobin content. Reference values for ESR differ according
to sex and age and are also influenced by pregnancy and obesity.
The ESR assay is difficult to standardise because of its sensitivity to parameters such as assay temperature,
vibration of the ESR tube, deviation of the tube from the vertical position, sample dilution and haematocrit.
CRP is a better inflammation marker than ESR.
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