Nutritional Methodology Folate Deficiency Does Not Alter the Usefulness of the Serum Transferrin Receptor Concentration as an Index for the Detection of Iron Deficiency in Mexican Women during Early Lactation

The purpose of this study was to investigate the usefulness of soluble serum transferrin receptor (TfR) concentration, TfR index and log TfR:ferritin ratio (TfR outcomes) in detecting tissue Fe deficiency among breast-feeding Otomi women residing in Capulhuac, Mexico (2800 m above sea level) and to determine whether folate deficiency modifies the interpretation of these data. Lactating women (n 68) provided blood samples at 22 13 d (mean SD) postpartum. Using the 3-index Fe assessment model with and without Hb, 2 women (3%) had Fe-deficient erythropoiesis, 24 (36%) Fe deficiency anemia, and 19 (29%) indeterminate Fe status; 29 (43%) and 5 (7.5%) women had plasma and erythrocyte folate concentrations below normative cutoff values, respectively. Mean values for TfR outcomes were higher among women classified as Fe deficient than those who were Fe sufficient, but did not differ with low or normal blood folate concentrations. Similarly, TfR outcomes did not differ among women with normocytic or macrocytic erythrocytes. Receiver-operating characteristic (ROC) curves generated for TfR outcomes yielded areas under the curve from 0.62 to 0.68, indicating that each of these measures, on its own, is a poor predictor of tissue Fe deficiency in lactating women. In conclusion, low blood folate concentrations or the presence of macrocytosis in Otomi women from Capulhuac, Mexico (moderate altitude) did not influence the utility of TfR outcomes for the detection of Fe deficiency during early lactation. Further, on their own, TfR, TfR index, and TfR:ferritin ratio were poor predictors of tissue Fe deficiency for any given individual. J. Nutr. 135: 144–149, 2005.