Which of the following results is indicative of iron deficiency?

Iron deficiency is characterized by a reduction in the size of red blood cells, leading to a condition known as microcytic anemia. A low mean corpuscular volume (MCV) indicates that the red blood cells are smaller than normal, which is a hallmark of iron deficiency anemia. This condition arises because iron is crucial for the production of hemoglobin; without sufficient iron, the body cannot produce adequately-sized red blood cells, thus resulting in a lower MCV.

In contrast, high MCV values typically suggest macrocytic anemia, which is often associated with vitamin B12 or folate deficiencies, not iron deficiency. Low folate levels can also lead to macrocytosis, further emphasizing the significance of understanding MCV in relation to specific types of anemia. Ferritin, which indicates the body's iron stores, is usually low in cases of iron deficiency, rather than high. Therefore, a low MCV effectively signifies that iron deficiency is present, reinforcing the importance of this parameter in diagnosing the condition.