Figure 3

Correlation between parasite densities determined by light microscopy and calculated by nested qPCR. Calculated parasite densities from nested qPCR were plotted against parasite densities determined by light microscopy for symptomatic infections (red circles), asymptomatic infections with positive blood smears (black circles), and asymptomatic infections with negative blood smears (unfilled circles). Parasite densities calculated by nested PCR strongly correlated with both asymptomatic (Pearson’s r = 0.58, 95% CI [0.29 to 0.77], P < 0.001) and symptomatic (Pearson’s r 0.70, 95% CI [0.53 to 0.81], P < 0.0001) P. falciparum infections. The dashed line represents the limit of detection for blood-smear microscopy (~40 parasites/μl).