Influence of iron saturation as a possible source of error in the immunoturbidimetric determination of serum transferrin.

The serum transferrin concentration is usually overestimated when assessed as total iron binding capacity, because iron binds not only to transferrin but also, non-specifically, to other serum proteins [l-3]. Transferrin concentration can be measured directly by immunochemical methods including: radial immunodiffusion [ 1,2,4-61, immunonephelometric assay [6,7] and immunoturbidimetric assay [8,9]. In the methods for direct transferrin determination published hitherto no attention has been paid to the effect of the iron concentration in serum samples on the formation of the immune-complex. This effect was studied for both the immunoturbidimetric assay and radial immunodiffusion.