Definition and oxygen-carrying impairment

Summary

Anemia (anaemia) is a blood disorder defined by a reduced ability of the blood to carry oxygen. This impairment can result from having fewer red blood cells than normal, having less hemoglobin available to transport oxygen, or having abnormalities in hemoglobin that interfere with its oxygen-carrying function. When anemia develops slowly, symptoms may be vague and include tiredness, weakness, shortness of breath, headaches, and reduced exercise tolerance; when it is acute, symptoms can be more severe and may include confusion, feeling faint or passing out, loss of consciousness, and increased thirst. Several definitions are used. A strict but broad definition is an absolute decrease in red blood cell mass, while a broader definition focuses on the lowered oxygen-carrying capacity of blood. An operational definition commonly used in practice is a decrease in whole-blood hemoglobin concentration to more than 2 standard deviations below the mean for age- and sex-matched reference ranges. The topic also notes that anemia is typically diagnosed using hemoglobin measurement from a complete blood count, and further testing is then used to determine the underlying cause.

Key Points

• 1

  Anemia is defined by reduced oxygen-carrying capacity of blood, due to fewer red blood cells, reduced hemoglobin for oxygen transport, or dysfunctional hemoglobin.

• 2

  Definitions range from decreased red blood cell mass to lowered blood oxygen-carrying ability; operationally it is often identified by hemoglobin levels below age- and sex-matched thresholds.

• 3

  Diagnosis starts with hemoglobin measurement (complete blood count), followed by additional tests to determine the cause.