The most sensitive single test for phenotypic detection of hereditary hemochromatosis reflects the percentage of sites available for carrying iron.

The most sensitive single test for phenotypic detection of hereditary hemochromatosis reflects the percentage of sites available for carrying iron.

• A. TIBC
• B. Serum iron level
• C. Serum ferritin
• D. Transferrin saturation

Answer: (A)

Transferrin saturation is the best single test for phenotypic detection because it directly shows how many of the transferrin iron-binding sites are occupied by iron. In hereditary hemochromatosis, iron absorption is increased, so more iron binds to transferrin and a larger fraction of the binding sites are filled. This makes transferrin saturation rise early and reliably. Transferrin saturation is calculated from serum iron and TIBC (transferrin’s total binding capacity) as (serum iron ÷ TIBC) × 100. In HH, serum iron tends to be elevated and TIBC can be normal or reduced, driving the saturation percentage up (often above ~45-50%). Other measures are less specific or reliable on their own. TIBC assesses capacity to bind iron but can be altered for reasons other than iron overload; serum iron varies daily and with inflammation; ferritin reflects stored iron but is an acute-phase reactant and can be elevated in many conditions, not just HH. So the percentage of transferrin binding sites occupied by iron—transferrin saturation—is the most sensitive single indicator of iron overload consistent with hereditary hemochromatosis.

Transferrin saturation is the best single test for phenotypic detection because it directly shows how many of the transferrin iron-binding sites are occupied by iron. In hereditary hemochromatosis, iron absorption is increased, so more iron binds to transferrin and a larger fraction of the binding sites are filled. This makes transferrin saturation rise early and reliably.

Transferrin saturation is calculated from serum iron and TIBC (transferrin’s total binding capacity) as (serum iron ÷ TIBC) × 100. In HH, serum iron tends to be elevated and TIBC can be normal or reduced, driving the saturation percentage up (often above ~45-50%).

Other measures are less specific or reliable on their own. TIBC assesses capacity to bind iron but can be altered for reasons other than iron overload; serum iron varies daily and with inflammation; ferritin reflects stored iron but is an acute-phase reactant and can be elevated in many conditions, not just HH.

So the percentage of transferrin binding sites occupied by iron—transferrin saturation—is the most sensitive single indicator of iron overload consistent with hereditary hemochromatosis.