Genotyping of Plasmodium falciparum infections by PCR: a comparative multicentre study

Genetic diversity of malaria parasites represents a major issue in understa nding several aspects of malaria infection and disease. Genotyping of Plasm odium falciparum infections with polymerase chain reaction (PCR)-based meth ods has therefore been introduced in epidemiological studies. Polymorphic r egions of the msp1, msp2 and glurp genes are the most frequently used marke rs for genotyping, but methods may differ. A multicentre study was therefor e conducted to evaluate the comparability of results from different laborat ories when the same samples were analysed. Analyses of laboratory-cloned li nes revealed high specificity but varying sensitivity. Detection of low-den sity clones was hampered in multiclonal infections. Analyses of isolates fr om Tanzania and Papua New Guinea revealed similar positivity rates with the same allelic types identified. The number of alleles detected per isolate, however, varied systematically between the laboratories especially at high parasite densities. When the analyses were repeated within the laboratorie s, high agreement was found in getting positive or negative results but wit h a random variation in the number of alleles detected. The msp2 locus appe ared to be the most informative single marker for analyses of multiplicity of infection. Genotyping by PCR is a powerful tool for studies on genetic d iversity of P. falciparum but this study has revealed limitations in compar ing results on multiplicity of infection derived from different laboratorie s and emphasizes the need for highly standardized laboratory protocols.