You suspect iron deficiency anemia in a 46 year old lady presenting with pallor. Which blood investigation result is NOT consistent with your provisional diagnosis?
A. Low levels of plasma ferritin
B. Decreased saturation of transferrin
C. Decreased level of hemoglobin
D. Decreased level of red cell protoporphyrin
Protoporphyrin is an intermediate in the pathway to heme synthesis. Under conditions in which heme synthesis is impaired, protoporphyrin accumulates within the red cell. Normal values are
The most common causes of increased red cell protoporphyrin levels are absolute or relative iron deficiency and lead poisoning.
Under steady-state conditions, the serum ferritin level correlates with total body iron stores; thus, the serum ferritin level is the most convenient laboratory test to estimate iron stores.
The TIBC (Total Iron Binding Capacity) is an indirect measure of the circulating transferrin. The normal range for the serum iron is 50–150 g/dL; the normal range for TIBC is 300–360 g/dL. Transferrin saturation, which is normally 25–50%, is obtained by the following formula: serum iron x 100 ÷ TIBC. Iron-deficiency states are associated with saturation levels below 20%.
Ref: Adamson J.W. (2012). Chapter 103. Iron Deficiency and Other Hypoproliferative Anemias. In D.L. Longo, A.S. Fauci, D.L. Kasper, S.L. Hauser, J.L. Jameson, J. Loscalzo (Eds), Harrison’s Principles of Internal Medicine, 18e.