Diagnostic Test Developed for Mixed Malaria Infections

A rapid diagnostic test (RDT) has been developed and evaluated as a mixed-species infections malaria antigen (FVM Ag) detection kit.

The kit, which uses monoclonal antibodies, can identify both single-species Plasmodium falciparum or P. vivax infections, and mixed infections with these two species.

Scientists at the Chungbuk National University (Republic of Korea) prepared colloidal gold–conjugated monoclonal antibodies applied to cellulose paper strips. They produced three monoclonal antibodies that recognize the lactate dehydrogenase of P. falciparum, P. vivax, or both to develop the first mixed-species infections malaria antigen-detection kit. They evaluated the sensitivity of the test and compared it with comparable commercial RDTs.

The sensitivity and specificity of the kit was assessed with 722 clinical specimens. The detection limit of 150 parasites/μL for the FVM Ag RDT for P. falciparum-positive blood samples was higher than that of the two commercial RDTs, which was less than 60 parasites/μL. The detection limit of the RDT for P. vivax-positive specimens was 250 parasites/μL, which was the same as that of the NanoSign Malaria Pf/Pan Ag kit (Bioland Ltd; Ochang, Korea) and lower than that of the 500 parasites/μL for the BioLine Malaria Pf/Pan Ag kit (Standard Diagnostics Inc.; Suwon, Korea). The results of the study showed that the FVM Ag RDT has sensitivities for P. falciparum, P. vivax, and mixed-species infection were 96.5%, 95.3%, and 85.7%, respectively. In addition, its specificity was as high as 99.4%.

P. falciparum and P. vivax malaria are endemic to many parts of the world and humans can be coinfected with both species. Because each Plasmodium species has different biological and clinical characteristics, accurate differentiation of the infecting species is essential for effective treatment. Although microscopy is still the gold standard for malaria diagnosis, it requires experienced technicians and a microscope, which are not always available in remote areas. The authors of the study concluded that the FVM Ag kit is the first RDT with the capability to differentiate malaria species. They anticipate that their RDT will be a useful diagnostic tool that will help improve the diagnosis and treatment of malaria, particularly in remote areas of the world. The study was published the December 2011 issue the American Journal of Tropical Medicine and Hygiene.

Related Links:
Chungbuk National University
Bioland Ltd.
Standard Diagnostics Inc.