Pseudoanemia

Dilutional phenomenon in endurance athletes causing hemoglobin and hematocrit values that are lower than established limits of normal

Plasma volume expansion by 10–20% with little change in red cell numbers (ie, oxygen-carrying capacity; red cell mass remains unchanged) (1)

Contributing factors include:

Theoretically, this increased blood volume decreases viscosity, thereby maximizing stroke volume, cardiac output, and subsequent oxygen delivery (2).

Hemodilution occurs over the 48 hr after every episode of endurance exercise and may persist for as long as 1 wk after discontinuing training.

If training continues, red cell mass will catch up with plasma volume expansion over the span of few weeks, causing hemoglobin and hematocrit values to normalize (3).

Synonym(s): Sports anemia; Athletes' pseudoanemia

Hemoglobin levels 13–14 g/100 mL in men and 11–12 g/100 mL in women; dose-response relationship between amount/intensity of exercise and hemoglobin drop (4)

Elite endurance athletes have a greater degree of dilutional pseudoanemia than more moderate endurance athletes.

Females are more likely than males to have iron-deficiency anemia with sports ± presence of pseudoanemia.

No particular symptoms or physical findings

Laboratory studies are performed if etiology unclear or symptoms are present.

Normal mean corpuscular volume

No hematuria or hemoglobinuria on urinalysis

Normal bilirubin and haptoglobin

Ferritin may be lower in endurance athletes owing to the same relative dilutional effect. Values often <60 µg/L, occasionally <30, but <15 = iron deficiency.

Iron-deficiency anemia

GI bleeding

Hematuria

Foot-strike hemolysis