Use of haemoglobin and ferritin to assess the need for and impact of use of iron fortified iodised salt

Diagnosis of anaemia is by Haemoglobin (Hb) estimation. The World Health Organisation (WHO) has recommended ferritin estimation for assessment of iron deficiency because of concordance between ferritin levels in blood and stainable iron in bone marrow cells. In view of the wide variations in ferritin levels between individuals, communities, in presence of inflammation and in response to interventions, WHO recommended that population based longitudinal studies should be taken up to assess usefulness of ferritin for assessing the need for and for monitoring the impact of interventions to improve iron status. Data from a 12-month longitudinal community-based open randomised trial to assess the impact of use of iron fortified iodised salt (DFS) were re-analysed to assess: usefulness of Hb and ferritin assays in assessing: need for use of iron fortified iodised salt (DFS) to improve Hb, and impact of 12-month use of DFS, usefulness of C Reactive Protein (CRP) assay in defining iron deficiency in presence of inflammation. Haemoglobin (Hb) is the stable final circulating product which reflects the impact of nutrient deficiencies and interventions to correct them. Hb is the optimal parameter for: diagnosis of anaemia and severity of anaemia in individuals, assessing prevalence of anaemia in communities and the need for public health intervention to improve Hb and assessing the impact of intervention to improve Hb status both at the individual level and in population groups. Both in men and women there was a progressive reduction in the mean ferritin with decreasing Hb level. Cut off of ferritin <15 ng/ml was useful for assessing prevalence of iron deficiency in women but not in men. Mean ferritin in women is useful for monitoring the impact of DFS in groups. Iron deficiency in women with inflammation could not be identified using CRP because most women with CRP ≥ 5 mg/L, had ferritin <70 ng/ml. Persistent inflammation (high CRP both at 0 and at 12 months) was not associated with lower mean Hb, as compared to those women who had no inflammation (CRP < 5 mg/L both at 0 and at 12 months).