WHO recommends prompt parasite-based diagnosis in all patients suspected of malaria before treatment is administered. Malaria rapid diagnostic tests (RDTs) have the potential to greatly improve the quality of management of malaria infections, especially in remote areas with limited access to good quality microscopy services.
RDTs are relatively simple to perform and interpret, they rapidly provide results, require limited training, and allow for the diagnosis of malaria at the community level.
Various types of RDTs on the market
Malaria RDTs detect specific antigens (proteins) produced by malaria parasites that are present in the blood of infected individuals. Some RDTs detect a single species (either P. falciparum or P. vivax), some detect multiple species (P. falciparum, P. vivax, P. malariae and P. ovale) and some further distinguish between P. falciparum and non-P. falciparum infection, or between specific species. Blood for the test is commonly obtained from a finger-prick and results are available within 15–30 minutes. Though there are variations among the more than 200 malaria RDT products on the market, the principles of the tests are similar.
Expansion in RDT use
In recent years, RDT testing has been significantly expanded around the world. Manufacturers surveyed for the World malaria report 2023reported that globally 3.9 billion RDTs for malaria were delivered between 2010 and 2022, with more than 82% of these sales being to sub-Saharan African countries. National malaria programmes distributed 345 million RDTs in 2022 – about 30 million more than in 2021.
Quality assurance and performance testing of RDTs
To assist ministries of health in endemic countries, UN agencies and major procurers, WHO, the Foundation for Innovative New Diagnostics (FIND) and the Centers for Disease Control and Prevention established a pre-purchase (Product Testing) and post-purchase (Lot Testing) evaluation scheme for RDTs in 2007. As a result of the periodic evaluations completed through this programme, the quality of RDTs has improved dramatically in recent years.
Further guidance on product selection and procurement
For procurement, WHO recommends that all RDTs be WHO-prequalified. A full list can be found on the WHO prequalification page related to Prequalified In Vitro Diagnostic products. All products that are WHO-prequalified meet the required minimum performance criteria and are considered acceptable for procurement and to diagnose clinical malaria. Products which exceed these minimum performance criteria are not expected to have any significant clinical benefit over those that just meet these criteria. All WHO prequalified malaria RDTs have a public report available that summarizes the assessment carried out, as well as any inspection of the manufacturing site(s) that manufacture that product.
In the case that no appropriate WHO-prequalified test is available (or there is very limited choice) to meet procurement needs, i.e. settings with a high prevalence (≥ 5%) of pfhrp2/3 gene deletions causing negative HRP2-RDT results, all procured RDTs should meet the following minimum requirements:
- i) ISO 13485 certified,
- ii) Product is in the WHO prequalification pipeline and has passed the laboratory evaluation achieving:
- at least a 75% "panel detection score" for low parasite density samples (200 p/µL) from the product testing evaluation panel for the detection ofP. falciparum (HRP2 expressing and nonHRP2 expressing panels) and, if applicable for P.vivax;
- a false positive rate of less than 10%; and
- fewer than 5% invalid tests.
NB. The panel detection score (PDS) is not the same as "sensitivity" which is measured in a real population where there is a variable mix of high and low density infections. The PDS at 200p/µL rather reflects how the test can be expected to perform when challenged at the lower limits of clinically significant parasitemia.
It is recommended that RDTs with high thermal stability be selected for use in areas with very high ambient temperature, ideally 40–45 °C.
For general inquiries, please contact [email protected] and for more details of the prequalification process contact [email protected]
