Unbound Iron Binding Capacity (UIBC) – An Alternative Lab Parameter for Iron Stores?

Introduction: Iron is a component of a number of proteins including haemoglobin, myoglobin, cytochromes and enzymes deficiency of which leads to iron deficiency anemia and excess in iron overload. There is a panel of tests to assess iron status in the body. A low serum iron & ferritin with an elevated TIBC are diagnostic of iron deficiency. While a low serum ferritin is virtually diagnostic of iron deficiency. AS ferritin is an acute phase reactant, it may not be a good marker for iron overload.

The objective of the study was to find out whether UIBC is an alternative lab parameter of iron storage/ overload compared to ferritin.

Methodology: In a retrospective study conducted, data of 118 patients were collected, who were categorized as iron deficient and those with iron overload. Ferritin, UIBC and serum iron were assayed and remaining parameters were calculated.ROC curves were constructed using SPSS version 16 software.

Results: Area under the curve (AUC) for ferritin as a marker of iron storage, AUC for UIBC, serum iron, TIBC and transferrin were 0.108, 0.607, 0.098, 0.098 respectively. In patients with iron depletion, it was observed that AUC was 0.371 and 0.566 respectively for ferritin and UIBC respectively.

Conclusion: Ferritin is a better marker of iron overload compared to UIBC, however, UIBC may be a better marker in iron store depletion. Entire iron panel if correlated and interpreted would be more useful in assessing iron stores.