Which serum test is most effective for early detection of iron deficiency?

The most effective serum test for early detection of iron deficiency is ferritin. Ferritin is a protein that stores iron in the body and reflects the amount of stored iron. When iron levels begin to decrease and iron deficiency starts, ferritin levels drop before there are any significant changes in hemoglobin or hematocrit levels. This makes ferritin a sensitive indicator of iron status, allowing for early identification of deficiency, even before anemia develops.

Other tests, such as hemoglobin and hematocrit, are more useful in diagnosing anemia resulting from iron deficiency once it has progressed, rather than detecting early iron depletion. Similarly, reticulocyte counts can indicate bone marrow response to anemia but do not directly measure iron stores. Therefore, ferritin is the most reliable biomarker for diagnosing early iron deficiency.