Walsh & Hoyt: Laboratory Findings

Laboratory abnormalities in patients with babesiosis include a hemolytic anemia that may be severe, a decreased concentration of haptoglobin in the serum, and an increased reticulocyte count. The percentage of erythrocytes that are parasitized in symptomatic patients usually ranges from 1 to 10% but may be as high as 85%. The total white blood cell count is usually normal or slightly decreased, but significant thrombocytopenia is common. The erythrocyte sedimentation rate is often elevated, in part because of the infection and in part because of the anemia. Urinalysis reveals both proteinuria and hemoglobinuria, and the concentration of both urea nitrogen and creatinine in the serum may be increased.