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CRP vs ESR in RA — SCE Rheumatology MCQ

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EasyAutoimmune SerologyCRP vs ESR in RASCE Rheumatology

A patient with RA has CRP of 28 mg/L and ESR of 45 mm/hr. Their rheumatologist uses CRP for the DAS28-CRP calculation. What are the key differences between CRP and ESR in monitoring RA?

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Correct answer: D — CRP responds more quickly to inflammatory changes (rises within hours normalises within days) while ESR changes more slowly (takes weeks to change). CRP is less affected by age sex and anaemia than ESR. DAS28-CRP and DAS28-ESR may give different disease activity classifications

CRP and ESR measure different aspects of the inflammatory response. CRP is produced by hepatocytes in response to IL-6 and rises rapidly (within 6-12 hours) and falls quickly (half-life 19 hours) making it responsive to acute inflammatory changes. ESR reflects plasma viscosity (affected by immunoglobulins fibrinogen) and changes slowly over weeks. ESR is affected by age sex (higher in women) anaemia and hypergammaglobulinaemia. CRP is more specific for acute inflammation. Importantly DAS28-CRP and DAS28-ESR use different formulas and may give different disease activity classifications. Neither on Tocilizumab is reliable as IL-6 blockade suppresses both.

Reference: EULAR 2022 RA recommendations