In the bone marrow, normoblasts containing iron granules (stainable) are known as sideroblasts. Erythrocytes (RBCs) that contain stainable iron are called siderocytes. Normally, about 33% of the normoblasts are sideroblasts. Other storage iron is readily identifiable in monophages in bone marrow particles on the marrow slides.

The bone marrow iron stain is the gold standard of iron deficiency: The presence of iron rules out iron deficiency. Marrow iron disappears before peripheral blood changes occur in iron-deficiency anemia. Only patients with decreased marrow iron are likely to benefit from iron therapy.

Bone marrow: 33% sideroblasts present

Peripheral blood: no siderocytes present

1. Make bone marrow slides (bone marrow biopsy material can be used), stain, and examine under the microscope for the presence of iron.

2. This test may also be done on peripheral blood for the detection of sideroblastic anemias.

1. Bone marrow iron is decreased in:

   1. Iron deficiency from all causes of chronic bleeding, hemorrhage, malignancy

   2. Polycythemia vera

   3. Pernicious anemia (early phase of therapy)

   4. Collagen diseases (e.g., RA, SLE)

   5. Infiltration of marrow by malignant lymphomas, carcinoma

   6. Chronic infection

   7. Myeloproliferative diseases

   8. Uremia

2. Bone marrow iron is increased in:

   1. Hemochromatosis (primary and secondary)

   2. Anemia, especially thalassemia major and minor, PNH, and other hemolytic anemias

   3. Megaloblastic anemia in relapse

   4. Chronic infections

   5. Chronic pancreatic insufficiency

Pretest Patient Care

1. See Pretest Patient Care for bone marrow aspiration.

2. Follow guidelines in Chapter 1 for safe, effective, informed pretest care.

Ingestion of iron dextran will bring values to normal despite other evidence of iron-deficiency anemia.