Detection of Plasmodium vivax and Plasmodium falciparum DNA in human saliva and urine: Loop-mediated isothermal amplification for malaria diagnosis

This study investigated loop-mediated isothermal amplification (LAMP) detection of Plasmodium falciparum and Plasmodium vivax in urine and saliva of malaria patients. From May to November 2011, 108 febrile patients referred to health centers in Sistan and Baluchestan Province of south-eastern Iran participated in the study. Saliva, urine, and blood samples were analyzed with nested PCR and LAMP targeting the species-specific nucleotide sequence of small subunit ribosomal RNA gene (18S rRNA) of P. falciparum and P. vivax and evaluated for diagnostic accuracy by comparison to blood nested PCR assay. When nested PCR of blood is used as standard, microscopy and nested PCR of saliva and urine samples showed sensitivity of 97.2%, 89.4% and 71% and specificity of 100%, 97.3% and 100%, respectively. LAMP sensitivity of blood, saliva, and urine was 95.8%, 47% and 29%, respectively, whereas LAMP specificity of these samples was 100%. Microscopy and nested PCR of saliva and LAMP of blood were comparable to nested PCR of blood (к = 0.95, 0.83, and 0.94, respectively), but agreement for nested PCR of urine was moderate (к = 0.64) and poor to fair for saliva LAMP and urine LAMP (к = 0.38 and 0.23, respectively). LAMP assay showed low sensitivity for detection of Plasmodium DNA in human saliva and urine compared to results with blood and to nested PCR of blood, saliva, and urine. However, considering the advantages of LAMP technology and of saliva and urine sampling, further research into the method is worthwhile. LAMP protocol and precise preparation protocols need to be defined and optimized for template DNA of saliva and urine.