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Serum Transferrin Saturation
TESTING FOR IRON OVERLOAD
Serum transferrin saturation measures the proportion of transferrin bound to iron, and is derived by dividing the serum iron by the total iron binding capacity. As such, it might therefore be expected to correlate with iron burden. However, the test has been found to be lacking in sensitivity,(1) as linearity becomes questionable once saturation levels >80% are reached, and the test has not yet proven to be useful in iron estimation for patients with transfusional iron overload.(2) For patients with hereditary iron overload, the test may be more useful.(3)
Serum transferrin saturation as a test for HH
Although it may not be a reliable test for iron overload, elevated serum transferrin saturation is a sensitive and specific disease marker for hereditary hemochromatosis. Fasting serum transferrin saturation >50% in women and >60% in men, has a sensitivity of 0.92, a specificity of 0.93, and a positive predictive value of 86% for the diagnosis of hereditary hemochromatosis.(4)
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Guidelines
The American Association for the Study of Liver
Diseases (AASLD) provides guidelines for the diagnosis and management of HH.
References
- * (1)Borgna-Pignatti C, Castriota-Scanderbeg A, Methods for evaluating iron stores and efficacy of chelation in transfusional hemosiderosis. Haematologica. 1991;76(5):409-13.
- * (2)Jensen PD, Jensen FT, Christensen T, et al, Evaluation of transfusional iron overload before and during iron chelation by magnetic resonance imaging of the liver and determination of serum ferritin in adult non-thalassaemic patients. Br J Haematol. 1995;89(4):880-9.
- * (3)Worwood M, The laboratory assessment of iron status--an update. Clin Chim Acta. 1997;259(1-2):3-23.
- * (4) Borwein S, Ghent CN, Valberg LS. Diagnostic efficacy of screening tests for hereditary hemochromatosis. Cen Med Assoc 1984;131:895-901