Improved detection of mixed P. falciparum-P. vivax infection at a rural health centre in Ethiopia using PCR.

This study aims to this study is to compare the co-infection Plasmodium falciparum + Plasmodium vivax and compare the detection of cases of mixed-species malaria using light microscopy versus semi-nested multiplex PCR (sPCR). Investigators collected 3060 samples at a rural health centre in Ethiopia from December 2010 to October 2011. Two capillary blood specimens were taken from each patient, one for diagnosis of Plasmodium infection by light microscopy and the other for sPCR-based diagnosis. LM detected 627 positive cases; these samples, together with 582 negatives by LM, were also subjected to sPCR testing. Of the 627 positive samples by LM, 68.4% were positive for P. vivax, 30.5% for P. falciparum, and 1.1% for P. falciparum + P. vivax co-infection. Using the sPCR technique, we identified 788 samples positive for Plasmodium: 33.0% for P. vivax, 26.5% for P. falciparum, 3.7% for P. falciparum + P. vivax co-infection, 2.0% for P. ovale and 0.8% for P. vivax + P. ovale co-infection. In the case of P. falciparum + P. vivax co-infection, light microscopy diagnosis showed a sensitivity of 11.1%, a specificity of 99.8%, a positive predictive value of 71.4% and a negative predictive value of 96.6%. The concordance rate for identifying P. falciparum + P. vivax co-infection (kappa statistic) with microscopy and sPCR was 0.184. The LM approach has low sensitivity for the detection of mixed-species infections, while sPCR is more useful.