A primer on anemia evaluation withcase presentations

Anemia represents a common problem encountered in daily clinical practice, affecting 3.4 million Americans. Hence, a structured approach to evaluating anemia is highly relevant in primary care. Multichannel automated analyzers have revolutionized the work of performing complete blood counts (CBCs). However, when interpreting results, clinicians must be aware of limitations encountered with these technologies, which can yield spurious red blood cell (RBC) values in certain clinical circumstances. Automated analyzers identify subpopulations of RBCs that are unexpectedly small or large or have unexpectedly low or high hemoglobin concentrations, thereby signifying aberrant RBC morphologies for review on peripheral blood smear. Results of various blood chemistries help to refine or confirm diagnostic considerations suggested by the CBC, reticulocyte count, and peripheral blood smear. Although tempo of anemia development may strongly support bleeding or hemolysis as the cause of anemia, kinetic changes in RBC mass, even due to these mechanisms, are often more subtle, suggesting possible underproduction causes of anemia. Abnormalities in white blood cell (WBC) counts, platelet counts, and WBC differentials may suggest disorders of trilineage hematopoiesis, although multiple competing factors may coexist, with certain factors affecting RBCs independent of those affecting WBCs and/or platelets. To focus diagnostic considerations, clinicians should consider anemia etiologies categorized by RBC size (mean cell volume, MCV) and morphology (eg, spherocytes, bite cells, schistocytes, target cells, teardrops). These categories include the microcytic, normocytic, and macrocytic anemias. Each of these categories are briefly reviewed, and case presentations are provided to illustrate specific points.