Is flow cytometry better in counting malaria pigment-containing leukocytes compared to microscopy?

BACKGROUND: Detection of malaria pigment (or haemozoin; Hz)-containing leukocytes may have prognostic relevance in malaria; however, studies reported conflicting results, with microscopic counts suggestive of being inaccurate and imprecise. METHODS: Numbers of Hz-containing leukocytes from a malaria patient obtained with a flow cytometer counting 50.000 gated events were compared with thin film microscopy as applied under field conditions. RESULTS: Flow cytometry identified 5.8% Hz-containing monocytes and 1.8% Hz-containing neutrophils. The microscopic examination yielded 10% and 13% of Hz-containing monocytes, as well as 0% and 0.5% of Hz-containing neutrophils for observers one and two, respectively. CONCLUSION: Novel, robust and affordable cytometric methods should be evaluated in the field as they may assist in utilizing Hz-containing cells as clinically useful parameter.