Evaluation of OptiMAL (R) assay test to detect imported malaria in Italy

This study evaluated a newly developed rapid malaria diagnostic test, OptiM AL(R) Assay, to detect: "Plamodium falciparum malaria" and "non Plasmodium falciparum malaria" in blood samples from 139 individuals with a presumptiv e clinical diagnosis of imported malaria in Italy. OptiMAL(R) Assay utilize s a dipstick coated with monoclonal antibodies against the intracellular me tabolic enzyme, plasmodium Lactate Dehydrogenase (pLDH) present in and rele ased from parasite-infected erythrocytes. Blood samples from 56 cases out of 139 were found "Plamodium falciparum mal aria" positive by microscopy; with these samples OptiMAL(R) Assay and the P araSight-F test, which is a kit detecting the P. falciparum histidin-rich p rotein 2 (HRP-2), showed an overall sensitivity of 83% and 94%, respectivel y, in comparison with microscopy. Parasitemia levels tested in the 56 P. falciparum positive blood samples by microscopy ranged from <0.004% to 20%. A correlation between sensitivity a nd parasitemia was evident and OptiMAL(R) Assay and ParaSight-F test were m ore sensitive (96-100%; 100%) with samples with 0.1% - 20% levels of parasi temia, while proved less sensitive (0-44%; 50-88%) with <0.004-0.01% levels of parasitemia. OptiMAL(R) Assay detected 6 cases out of 10 of "non Plasmodium falciparum m alaria" and a correlation between sensitivity and parasitemia was very diff icult to define because of the low number of samples tested in our study. W e also tested a series of 18 rheumatoid factor (RF) positive and malaria ne gative specimens by using OptiMAL(R) Assay, observing an overall false-posi tive rate of 11% (2 of 18 specimens). We conclude that the OptiMAL(R) Assay might be an important diagnostic tool for the rapid diagnosis of imported malaria in Italy.