Is CRP, like ESR, Age and Gender Dependent?

C-reactive protein (CRP) and the erythrocyte sedimentation rate (ESR) are often ordered together in patients suspected of having inflammatory or infectious disorders. ESRs are higher in women than in men and they also increases with age, although most laboratory reference ranges only take gender into account. It is unclear whether CRP, like ESR, differs between women and men and/or increases with age. We analyzed 382 consecutive patients in whom the CRP and ESR were both within the laboratory’s reference range. ESR was, as expected, ≈5 mm/h higher in the 236 women than in the 146 men (P<0.0001). ESR was significantly correlated with patient age (P=0.0012). In contrast to ESR, CRP levels were identical in women and men and there was no correlation between CRP and patient age. Thus, laboratories should adjust the ESR reference range for gender and age, but this adjustment is not necessary for CRP.