Their work demonstrated that this index has a better sensitivity for iron deficiency than ferritin alone, although in older adults a low ferritin in the presence of a raised CRP has high predictive value for anaemia,25 suggesting that a low ferritin is a useful rule in test but a normal ferritin should not be used to exclude an iron deficiency anaemia particularly if there is evidence of any degree of inflammation. The gene discussed is CRP; the disease is anemia.