Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (291 page)

   If serum ferritin is normal or borderline, serum iron and transferrin (usually reported as TIBC) are the next assay to be ordered.

   If the serum iron is very low and TIBC elevated (with the ratio of serum iron divided by TIBC <16%), diagnosis is confirmed.

   Normal serum iron and TIBC: iron deficiency is excluded in most cases.

   Low serum iron, low TIBC: most likely anemia of chronic disease; workup underlying etiology.

   High serum iron, normal TIBC: the most likely diagnosis is thalassemia.

   Two additional blood tests: the soluble transferrin receptor and the reticulocyte Hb content are optional. When used in conjunction with ferritin, these tests improve further our ability to accurately diagnose iron deficiency. Not widely used.

   As a last resort, if the diagnosis is still in doubt: bone marrow aspirate/biopsy for Prussian blue stain. If it is negative, iron deficiency is definitely present.

NORMOCYTIC ANEMIAS

   Definition

Anemias with normal MCV.

   Who Should Be Suspected?

Patients with anemias secondary to an underlying nonhematologic disease (also known as “anemias of chronic disease” [ACD]). The term “anemia of chronic inflammation” may be used too, but it does not cover all situations (see the following paragraph). The most common conditions leading to ACD:

   Anemia of chronic inflammation (infections, rheumatologic diseases) is the prototype of normocytic anemias; the red cell may occasionally be borderline microcytic.

   The etiology of anemia of chronic renal failure is in part the reduced production of erythropoietin; additional factors are a shortened red cell survival and frequent bleeding.

   Anemia in cancer patients is a common, multifactorial finding. Microangiopathic hemolytic anemia and myelophthisic anemia may be an additional feature resulting from disseminated carcinoma.

   Aplastic anemias (AAs) can be congenital or acquired. In AA, hematopoiesis fails. All blood lineages are decreased (pancytopenia), with the possible exception of lymphocytes. Pure red cell anemia is a variant of AA in which only, or mostly, the red cell line is affected.