Intraleucocytic malaria pigment and prognosis in severe malaria

Abstract

The quantity of malaria pigment liberated into the circulation at schizogony reflects the pathogenic sequestered parasite burden in Plasmodium falciparum malaria, and may therefore be a measure of disease severity. Among 300 consecutive adult patients with severe falciparum malaria, the 40 who died had significantly higher proportions of malaria pigment-containing neutrophils on admission (mean = 7·7%, standard deviation ( sd) = 5·9%) and pigment-containing monocytes (mean = 8·6%, SD = 5·9%) than did survivors (mean 3·2%, sd = 4·1% and mean 4·8%, sd = 4·6%, respectively) ( P < 0·0001): This proved a better indicator of prognosis than the peripheral parasite count. A count of peripheral neutrophils containing visible pigment ⩾5% predicted a fatal outcome with 73% sensitivity and 77% specificity (relative risk 6·2, 95% confidence interval (CI) 3·2–11·8) compared to 60% sensitivity and 57% specificity for parasitaemia >100 000/μL (relative risk 1·8, 95% CI 1·0–3·3). The peripheral blood count of pigment-containing neutrophils in severe malaria is a rapid, simple, and practical prognostic test.