Transferrin--a poor measure of nutritional status

The present study evaluated the sensitivity and specificity of the serum transferrin concentration as a measure of the nutritional state. Serum transferrin was derived from total iron-binding capacity measurements in 74 patients on 114 occasions and correlated with body composition as measured by multiple isotope dilution. Highly significant correlations (p less than 0.001) existed between serum transferrin and both the body cell mass and the nutritional state as measured by the Nae/Ke ratio. However, the 95% confidence limits about both regressions were wide. The false-positive rate was 60% while the false-negative rate was 31%. Body composition and transferrin were measured before and after 2 wk of total parenteral nutrition in 34 malnourished patients. Eighteen patients restored body cell mass toward normal after 2 wk of total parenteral nutrition while in 16 patients the body cell mass continued to decrease in size, despite 2 wk of total parenteral nutrition. The changes in serum transferrin were not significant over this period of time in either group, despite significant changes in the nutritional state in both groups. The presence of a statistically significant relationship between the serum transferrin concentration and the nutritional state indicates that the serum transferrin concentration accurately reflects a population's nutritional status, and is therefore useful in epidemiologic surveys. However, because of the large variance of the data, as demonstrated by the wide 95% confidence limits, and because of the poor sensitivity and specificity, in an individual patient it is of little value as a measure of the nutritional status.