Immunobiology of mild micronutrient deficiencies

Serum transferrin receptor in children with respiratory infections

OBJECTIVE

To study the effect of infection on iron status in children suffering from acute, mild or severe respiratory infections and to determine the nature of anemia in infection using serum transferrin receptor (sTfR) levels.

DESIGN

Forty-three children aged between 3 and 5 y with no evidence of infection and receiving iron supplements in the preceding 100 days served as controls. Twenty-one children with mild upper respiratory infection and 94 children hospitalized for acute pneumonia constituted the experimental group. Hemoglobin (Hb), sTfR and serum ferritin were estimated in all the children at the time of diagnosis and again on the 15th and 30th days after the infection in those who were available for follow-up.

RESULTS

Mean (95% CI) sTfR was 6.08 (5.1-7.1) mg/l in healthy non-anemic children. Upper respiratory infection had no impact on Hb or sTfR but it significantly elevated serum ferritin levels. Eighty-three percent of the children with pneumonia had Hb less than 110 g/l at the time of diagnosis and had elevated mean sTfR, 18.0 (15.7-20.3) mg/l. There was a decline in mean sTfR by the 15th day of infection to 14.3 (11.3-17.4) mg/l with further rise to 22.9 (13.0-31.9) mg/l by 30 days. Serum ferritin was significantly elevated at the time of diagnosis (85.9; 71.1-100.8 micro g/l) as well as at 15 days (89.1; 68-110.1 micro g/l) with a decline by 30 days.

CONCLUSIONS

Severe lower respiratory infection exaggerates iron-deficient erythropoiesis by blocking release of iron from the storage pools. sTfR may not be a sensitive and specific tool of assessing true iron status of children exposed to severe infections.