Clinical evaluation of iron deficiency.

While the prevalence of iron deficiency has remained relatively constant, there has been continuing refinement in its laboratory recognition, especially with the recent introduction of serum ferritin and FEP measurements. It is helpful to classify iron deficiency into three stages. Storage iron depletion is identified by marrow examination or serum ferritin, iron deficient erythropoiesis by TS, FEP, or MCV, and iron deficiency anemia by hemoglobin concentration or therapeutic iron trial. Combinations of these measurements have been used in prevalence studies to obtain a quantitative measure of body iron stores. The optimal laboratory approach to diagnosing iron deficiency depends on the clinical setting. In the office or outpatient clinic, iron depletion is best recognized by the serum ferritin, although the TS, FEP, and MCV are helpful in gauging its severity. In hospitalized patients with overt anemia, the TS, FEP, and MCV are much less helpful because similar changes are seen in the anemia of chronic disease. Examination of marrow iron remains the method of choice, especially in patients with infection, chronic disease, malignancy, or liver disease, although in many clinical situations the same information can be obtained from a serum ferritin. Serial measurements of serum ferritin have been particularly useful in monitoring patients at high risk of iron deficiency such as those with rheumatoid arthritis, chronic inflammatory bowel disease, or chronic renal failure.