Serum ferritin is the best indicator of a response to an intervention to control iron deficiency and should be measured with the haemoglobin concentration in all programme evaluations. In circumstances in which iron deficiency is the major cause of anaemia, the haemoglobin concentration may improve more rapidly than the serum ferritin concentration. In circumstances in which the serum ferritin concentration improves (even when inflammation is common) but the haemoglobin concentration does not, factors in addition to iron are likely to be the cause of anaemia.
If funding is available, it could also be useful to measure the concentration of one or both of the acute phase proteins CRP or AGP, to account for a high serum ferritin concentration caused by inflammation. Individuals with high values for the acute phase protein should be excluded from the analysis, if possible, depending on the limitations imposed by the sample size of the dataset and the consequent translation of the results to define the iron status of the general population. This is particularly important when repeated surveys are done and there is no control group for the intervention.
If funding is available, the transferrin receptor should be measured during repeated surveys to classify populations. The combination of serum ferritin and transferrin receptor may also be used to estimate body iron stores in populations (12). The calculation of body iron stores is not essential but can be useful to estimate the amount of iron that is absorbed during an intervention and to demonstrate a decrease in iron deficiency. However, since the method uses measurements of serum ferritin concentration, infection may again be a confounding factor, so an acute phase protein should be measured to exclude individuals with a high concentration.