Comparison of washed and unwashed specimens in the Plasmodium falciparum in vitro microculture drug assay.

The dose response of Plasmodium falciparum isolates in the standard in vitro assay for drug resistance was compared using blood specimens which were centrifuged and washed before cultivation. Washing of the cultures increased the success of cultivation by greater than 100%. Eight cultures which grew using both methods gave similar results in the determination of resistance or sensitivity. The ED50 as determined by probit analysis, was approximately 50% higher in parasites which had been washed before cultivation.