Ordering a Transferrin Saturation Test

In February 1997, a panel of medical experts convened by the CDC recommended that transferrin saturation (TS) be used as the initial diagnostic test for hereditary hemochromatosis.

The most frequently used method for determining TS requires an assay of serum iron and the total iron-binding capacity (TIBC) of serum proteins.

Serum iron is a measure of circulating iron bound to transferrin and reflects total body iron. Because serum iron measurements may be affected by menstrual cycle, time of day, diet, hepatitis, and use of iron containing placebos found in some oral contraceptive packages, serum iron levels alone are not sensitive indicators of iron status.

The major iron-binding and transport protein in serum is transferrin, although small amounts of iron may be bound to ferritin, albumin, and other proteins or compounds.

Transferrin levels, along with serum iron levels as part of the TIBC test, are useful in the differential diagnosis of many disorders, including hemochromatosis (Witte DL, 1996).

Transferrin saturation (TS) can be determined by two common methods:

  1. Measurement of TIBC. TS = (serum iron/TIBC x 100).
  2. Sum of measured unsaturated iron-binding capacity (UIBC) and measured serum iron.
    TS = (serum iron/ [serum iron + UIBC] x 100).
Note: Few laboratory order forms will have TS category lines. Ordering serum iron and a TIBC will allow for the calculation of TS. If TIBC is not an option, order serum iron and UIBC.

 
lab form
Lab forms are not standard. Ordering iron (cpt 83540) will not result in the calculation of transferrin saturation. Make sure to check the box for both iron & tibc (cpt 83550). Some labs use iron and uibc. Serum ferritin may be ordered at the same time and is often listed as ferritin, serum (cpt 82728).