Effect of saponin treatment on PicoGreen® fluorescence. PicoGreen® fluorescence is shown following saponin treatment, followed by washing to remove haemoglobin (■), or with no saponin treatment (○), of the parasite culture (1 – 10% parasitaemia). Background fluorescence was subtracted from each point. Lines were calculated by linear regression. The slope of the line for fluorescence in the absence of saponin treatment was significantly different from zero (P = 0.005; F-test), but was only 1.5% of the slope for fluorescence after removal of haemoglobin (87 ± 4 versus 1.3 ± 0.3 A.U./% parasitaemia).