Anemia Classification and Management

Definition and Diagnosis

The World Health Organization (WHO) defines anemia as a hemoglobin concentration <13.0 g/dL in adult men and <12.0 g/dL in non-pregnant adult women, with additional severity classifications based on these thresholds 1, 2, 3
For adult men, hemoglobin <13.0 g/dL is considered anemic 1, 2, 4
For non-pregnant adult women, hemoglobin <12.0 g/dL is considered anemic 1, 2, 4
For pregnant women, hemoglobin <11.0 g/dL is considered anemic 2, 3
For children 6 months to 5 years, hemoglobin <11.0 g/dL is considered anemic 2
For children 5 to 11 years, hemoglobin <11.5 g/dL is considered anemic 2
For children 12 to 13 years, hemoglobin <12.0 g/dL is considered anemic 2

The WHO establishes specific severity categories for women ≥15 years based on hemoglobin concentrations: mild anemia (11.0-11.9 g/dL) 6, moderate anemia (8.0-10.9 g/dL) 5, and severe anemia (<8.0 g/dL) 7

In chronic kidney disease, American guidelines recommend investigating anemia with hemoglobin <13.5 g/dL in men and <12.0 g/dL in women 8, 9
In cardiovascular surgery and perioperative care, maintaining hemoglobin ≥13.0 g/dL in all patients regardless of sex is recommended to optimize outcomes 7
The current WHO thresholds were established in 1968 based on predominantly Caucasian populations in Europe and North America 8
No adjustment of thresholds for age in men is recommended, as low hemoglobin levels in elderly frequently reflect underlying pathology 8

Once anemia is identified according to WHO criteria, evaluation should include erythrocyte indices (mean corpuscular volume, mean corpuscular hemoglobin, red cell distribution width) 2, iron studies (serum ferritin, transferrin saturation, serum iron) 5, inflammatory markers (C-reactive protein) 2, and reticulocyte count 4
Ferritin <100 ng/mL with transferrin saturation <20% indicates iron deficiency, although ferritin may be falsely elevated in inflammatory states 1, 7

Even mild anemia according to WHO criteria is associated with increased perioperative morbidity and mortality, respiratory, septic, and thromboembolic complications, myocardial injury, and cardiovascular events 7
Cognitive decline in elderly individuals is also associated with anemia 2
Preoperative correction of anemia with iron (oral or intravenous) reduces transfusions and improves outcomes, especially when administered 2-4 weeks before elective surgery 7