Protein profile and iron deficiency: value of the study of the albumin-transferrin couple

Abstract

From a clinical standpoint, the search for iron deficiency is based upon serum ferritin. However, serumferritin values may be pathologic in other numerous pathological conditions such as inflammation, liver diseases, malignant hematologic disorders, hemolysis, etc. Proteic profile combines the analyze of proteins variations: protein results are converted in percent of normal values referenced for the technique used. It has been suggested that on the protein profile, an increase in serum transferrin level compared to a normal serum albumin level (DAT: difference albumin-transferrin), appears early in the course of iron deficiency. In order to know the value of a pathologic DAT > or = 28% in the diagnosis of iron deficiency, we prospectively studied 156 patients consecutively hospitalized in an internal medicine department. Iron deficiency was defined by a low serum ferritin level. Diagnosis performance (sensitivity, specificity, positive and negative predictive values) of different biologic markers of iron deficiency (serum iron, saturation of total iron-binding capacity, low mean erythrocyte volume) and DAT was compared to the performance of low serum ferritin values. With the exception of low serum ferritin (which have by definition a specificity and a positive predictive value of 100%), pathologic DAT appeared as the best index of iron deficiency with the highest sensitivity (67.4%), specificity (97.3%), positive predictive value (91.2%), negative predicitive value (87.7%) and diagnosis efficacy (sensitivity x specificity = 0.66). A pathologic DAT associated to a low serum ferritin level increased the diagnosis performance of both tests to 0.72. Diagnosis efficacy of DAT was not changed (0.66) in 83 patients with a confounding factor for serum ferritin analysis (inflammation, liver diseases, malignant hematologic disorders, hemolysis) when diagnosis efficacy of all other tests decreased. There was a negative correlation between serum ferritin level and DAT level (r = 0.55; P < 0.0001). In conclusion, an increase of serum transferrin of more than 28% compared to serum albumin on a proteic profile gives a significant benefit for the diagnosis of iron deficiency. This benefit increases when data of both DAT and serum ferritin are associated.