Which test is not useful for diagnosing iron deficiency when given an iron profile with normal results?

When evaluating the useful tests for diagnosing iron deficiency, it's important to consider the nature of the test and what it is designed to measure. Hemoglobin electrophoresis is primarily used to identify different types of hemoglobin and detect hemoglobinopathies, such as sickle cell disease or thalassemia. It does not provide direct information regarding iron status or deficiency.

Normal results on an iron profile indicate that parameters such as serum iron, ferritin, and transferrin saturation are within typical ranges. An iron profile with normal results suggests that iron deficiency is unlikely. Hence, since hemoglobin electrophoresis is not focused on assessing iron levels or deficiency—rather it highlights abnormalities in hemoglobin types—it is not useful for diagnosing iron deficiency under these circumstances.

In contrast, serum transferrin levels can indicate iron deficiency when correlated with other parameters, and erythrocyte zinc protoporphyrin can increase in response to iron deficiency. Protein electrophoresis may also provide additional insight into blood protein compositions, which can indirectly point to underlying nutritional deficiencies, including iron.