Birefringent hemozoin identifies malaria

Abstract

The diagnosis of malaria is still sometimes difficult because of the insensitivity of microscopic screening at low levels of parasitemia. The malarial pigment, hemozoin, is a crystalline product of the digestion of hemoglobin by the parasites. Under polarized light at 500X magnification, brilliantly birefringent granules of the pigment were detected in Wright's stained smears, and the parasites easily localized, in 18 cases of malarial infection. Fresh, wet, coverslipped preparations of cultures of Plasmodium falciparum also were examined under polarized light. Serial dilutions of the cultures showed that, even at the very low level of 0.01% parasitemia, intracellular birefringent granules were detected in an average of 45 +/- 16 (SE) seconds at 500X magnification. Using polarized light is a simple, fast, sensitive, and specific method for localizing intracellular pigmented malaria parasites in wet preparations of blood.