Flow cytometric enumeration of parasitemia in cultures of Plasmodium falciparum stained with SYBR Green I and CD235A.

A flow cytometric (FACS) detection method for Plasmodium falciparum cultures (P. falciparum) was developed using SYBR Green I and CD235A and compared against the Giemsa stained microscopic examination. The cultured P. falciparum were spiked into red blood cells (RBCs) to yield parasitemia, ranging from 0.01% to 22.0%. FACS analysis demonstrated a clear separation between P. falciparum infected and uninfected RBCs. The measured percentage of parasitemia by FACS revealed higher precision (CV of 2.2-37.2%) with the sensitivity of 0.01% parasitemia than Giemsa stained microscopic examination (CV of 7.2-66.0%). High correlation of measured parasitaemia (r=0.98, P<0.05) was observed between FACS and Giemsa stained microscopic analyses. The higher levels of parasitaemia detection were observed in all ranges by FACS in comparison to Giemsa stained microscopic analysis. The currently reported FACS method using SYBR Green I and CD235A is potentially useful for measuring parasitemia in treating patients.