Anemia has been classified using several different schemes: degree of anemia/hemoglobin or hematocrit levels, etiology, pathophysiology, and red blood cell morphology.
Hemoglobin Levels
As described on the previous page, the reference ranges for hemoglobin determination vary by method of determination, age, and gender. Geography and race can also impact reference ranges. In an article by Badireddy and Baradhi (2023), the authors identified the following stages of anemia based on hemoglobin levels.5 These will vary based on gender, age, demographics, geography, and laboratory assay principles.
- Mild anemia: 100 g/L (10.0 g/dL) to normal
- Moderate anemia: 80-100 g/L (8.0-10.0 g/dL)
- Severe anemia: 65-79 g/L (6.5-7.9 g/dL)
- Life threatening anemia: <65 g/L (<6.5 g/dL)
Etiology
Understanding the cause, or etiology, of anemia is necessary to identify possible treatment options. Causes of anemia may include blood loss, nutritional deficiencies, genetics, toxins, infections, and malignancies, as well as those conditions in which a cause cannot be determined (idiopathic).
Pathophysiology
The classification of anemia by physiology can be simplified into two major areas:
- Those caused by increased destruction of red blood cells (including blood loss)
- Those caused by a decrease in the production of red blood cells (or hemoglobin)
Morphology
From a laboratory perspective, we classify anemia based on the morphology of the red blood cells, specifically as associated with our red blood cell indices: mean corpuscular (cell) hemoglobin (MCH), mean corpuscular volume (MCV), mean corpuscular hemoglobin concentration (MCHC).
