Rapid diagnostic tests (RDTs)
Malaria rapid diagnostic tests (RDTs) assist in the diagnosis of malaria by detecting evidence of malaria parasites (antigens) in human blood. These tests require a drop of peripheral blood, normally collected from a finger or heel prick. Visual read-outs are available typically within 20 mins or less.
RTDs are available in various formats (dipstick, cassette or hybrids). Regardless of the format, they are typically very simply to use, requiring no specialist services and minimal training. They require no infrastructure or apparatus and can be used at the point-of-care, including in very remote areas.
RDTs work by capturing dye-labelled antibodies bound to specific parasite antigens. There the most suitable antigen for the species-specific detection of P. vivax is the parasite lactate dehydrogenase (pLDH).1 While the sensitivity of pLDH-detecting RDTs is often not as good as that achieved by HRP2-based RDTs for P. falciparum, a number of initiatives are ongoing to develop P. vivax RDTs that do have significantly improved sensitivity – with the objective of reducing the number of missed P. vivax clinical cases.
Antibodies and antigens currently used for the detection of Plasmodium spp.
|Antibody||Antigen detected||Species recognized|
|Anti Pv-pLDH||pLDH||P. vivax|
|Anti Pvom-LDH||pLDH||P. vivax, P. ovale, P. malariae|
|Anti Aldolase||Aldolase||All Plasmodium species|
|Anti pan pLDH||pLDH||All Plasmodium species|
|Anti Pf-pLDH||pLDH||P. falciparum|
|Anti HRP2||HRP2||P. falciparum|
HRP2: Histidine rich protein 2
RDTs for P. vivax have relatively poor performance compared with those for P. falciparum, and uptake has been slow and inconsistent.3 This is due to a combination of lower parasite density in P. vivax infections, lower expression of the specific antigen being detected for this species, and poorer performance of the reagents used for this specific antigen. As a consequence, many RDTs might fail to detect P. vivax in samples containing 200 parasites/µL.
The RDTs that can be procured through the Global Fund to Fight AIDS, Tuberculosis and Malaria are listed on the World Health Organisation's list of prequalified in vitro diagnostics.