Iron status assessment in infants using hemoglobin, serum ferritin, and additional biomarkers

Iron deficiency and anemia are common in infants; however, assessing iron status in this population remains a challenge. This study aimed to assess iron status during the first year of life using biomarkers such as hemoglobin (Hb), mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), serum ferritin (SF), and zinc protoporphyrin (ZnPP). We analyzed data from a cohort of 1,083 infants followed between 2003 and 2006. Venous blood samples were taken at 3, 6, 9, and 12 months of age to determine Hb, SF, MCV, MCH, and ZnPP. Iron status was classified as normal, iron deficiency (ID), iron deficiency anemia (IDA), or anemia not related to ID (non-IDA). The kappa coefficient was used to evaluate the agreement between classifications of iron status based on different combinations of biomarkers and that obtained using Hb and SF levels. At 3, 6, 9, and 12 months of age, using SF and Hb, 89.9%, 82%, 85%, and 84% of infants, respectively, had normal iron status. The prevalence of ID was 5.6%, 11.5%, 10.1%, and 8.3%, while the prevalence of anemia was 4.5%, 6.6%, 4.9%, and 7.7%, with 2.1%, 15.9%, 23.7%, and 26.2% of cases classified as IDA. When ZnPP, SF, and Hb were used, the prevalence of ID increased to 20.2%, 27.7%, 27.2%, and 26%, and 23.3%, 39.0%, 60%, and 49.2% of anemia cases were classified as IDA at 3, 6, 9, and 12 months of age, respectively. Agreement in the classification of iron status using Hb and SF compared to Hb plus other biomarkers to identify ID was lower when ZnPP was included. At 3 months of age, the iron status of most infants was normal. However, from 6 months onward, 9% to 37% of infants were classified with ID and 4.9% to 7.7% developed anemia, with variation depending on the biomarkers used. Notably, more than half of the anemia was classified as non-IDA. Further research is needed on the diagnosis of iron status, appropriate biomarkers and their reference intervals in infants, as well as on strategies to prevent iron deficiency and anemia.