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Notes:
Like ferritin, TR has its limitations. TR assays are costly, about 3-4 fold more expensive than ferritin assays which are about $4.00/assay.
Serum TR may be elevated without functional iron depletion in conditions associated with an expanded bone marrow such as haemolytic anaemias, ineffective erythropoiesis
associated with megaloblastic anaemia, myelodysplasia and haemoglobinopathies such as thalassemia major.
Serum TR may also be raised when expanded effective erythropoiesis occurs, such as in polycythemia.
Because TR and ferritin concentrations change reciprocally with iron depletion, it has been suggested that the TR/ferritin ratio be used. This ratio is less than 100 with adequate iron stores and reaches over 2,000 at the point at which the functional compartment becomes depleted; 500 is the point where the storage compartment becomes depleted. The ratio works well in separating iron deficiency from anaemia of chronic disease
with a diagnostic accuracy of 92 %.
