Adult-Gerontology Clinical Nurse Specialist (CNS) Practice Exam

Which laboratory test is performed to identify the first stage of iron depletion?

1. Serum ferritin level

2. Transferrin saturation

3. Erythrocyte protoporphyrin

4. Mean corpuscular volume

The correct answer is: Serum ferritin level

The serum ferritin level is a key laboratory test used to identify the initial stage of iron depletion. Ferritin is a protein that stores iron, and its levels reflect the amount of stored iron in the body. In the first stage of iron depletion, the ferritin levels begin to decrease as the body’s iron stores are used up, even before any changes in the production of red blood cells or hemoglobin levels occur. This test is particularly valuable because it allows for early detection of iron deficiency before the individual progresses to more advanced stages, such as iron deficiency anemia, where changes in hemoglobin and other parameters become evident. Monitoring serum ferritin levels is essential in populations at risk for iron deficiency, such as women of childbearing age, pregnant individuals, and those with chronic blood loss. Other tests, such as transferrin saturation, erythrocyte protoporphyrin, and mean corpuscular volume, can provide additional information about iron status and anemia but are not as sensitive as serum ferritin for identifying the first stage of iron depletion. Transferrin saturation measures the amount of transferrin that is saturated with iron, which often becomes abnormal at later stages of deficiency. Erythrocyte protoporphyrin reflects