Hemolytic Anemia

Excerpt

Anemia is defined as a decrease in hemoglobin levels relative to an individual's baseline; however, sex- and race-specific reference ranges are often used to diagnose anemia when baseline hemoglobin is unknown. The World Health Organization (WHO) criteria for anemia in men are <13 g/dL, whereas for women, they are <12 g/dL. There are revised criteria for anemia in men and women with chemotherapy-related complications, as well as for age and race. Even "special populations" such as athletes, smokers, older adults, or those living at high altitudes have been reported to have different ranges.

The critical issue in evaluating any form of anemia is the early recognition of treatable causes. This is crucial because hemoglobin, an iron-rich protein, enables red blood cells (RBCs) to carry oxygen from the lungs to the rest of the body. The biconcave shape of RBCs enables optimal gas exchange. If the body is unable to deliver oxygen, one may experience symptoms such as weakness, lethargy, dizziness, headache, shortness of breath, or arrhythmias.

Anemia is often subcategorized into microcytic, normocytic, and macrocytic based on mean corpuscular volume (MCV). As there are numerous types of anemia, this laboratory parameter allows clinicians to formulate a practical diagnostic approach.

Hemolytic anemia is classified as normocytic anemia with an MCV of 80 to 100 fL. It is a form of low hemoglobin due to red blood cell destruction, increased hemoglobin catabolism, decreased hemoglobin levels, and increased bone marrow efforts to regenerate products. Hemolytic Anemias can be further subdivided into intrinsic and extrinsic causes.