The largest-ever independent, laboratory-based evaluation of rapid diagnostic tests (RDTs) for malaria has shown that some tests on the market perform exceptionally well in tropical temperatures and can detect even low parasite densities in blood samples, while other tests can detect parasites only at high densities.
The evaluation was co-sponsored by the WHO Regional Office for the Western Pacific (WPRO), WHO-based Special Programme for Research and Training in Tropical Diseases (TDR) and the Foundation for Innovative New Diagnostics (FIND). Testing was performed at the US Centers for Disease Control and Prevention (CDC). Forty one commercially available RDTs went through a blinded laboratory evaluation.
The findings will serve as a tool for countries to make informed choices, from among the dozens of tests commercially available, on the purchase and use of rapid diagnostics that are best suited to local conditions.
This performance evaluation will also inform procurement and prioritization for diagnostic test entry into WHO Prequalification Diagnostics Programme and WHO Procurement Schemes. Donor agencies also regularly refer to WHO recommendations on diagnostics when making their own purchases.
Surveillance and quality assurance
"This is an important first step in establishing a broader system of diagnostics surveillance and quality assurance to ensure sound and accurate diagnosis of malaria in poor and remote settings," said Dr Robert Ridley, Director of TDR.
"These evaluations provide us with a mechanism to evaluate RDT performance in a standardized way so that WHO, donors and country health ministries can identify those tests that perform best for their needs and particular settings," he added.
“While some tests clearly outperform others in terms of identifying malaria in populations of low parasite density, such as newborns or people sleeping under bednets, there are a whole range of criteria related to local conditions of malaria transmission and illness that need to be considered in country and donor procurement decisions,” said Giorgio Roscigno, CEO of FIND.
In addition to product testing WHO, TDR and FIND have also collaborated to establish procedures and quality assured facilities for routine lot testing of rapid diagnostics in Asia and Africa.
During the evaluation, samples of blood from patients infected with P. falciparum and P. vivax (the two major plasmodium species that cause malaria) in diverse geographic locations were diluted to achieve both a low parasite density (200 parasites/µl) and high parasite densities (2000 or 5000 parasites/µl). At low parasite density, samples were tested against two rapid tests per lot (2 lots) and at high parasite density samples were tested against one rapid test per lot (2 lots).
Among the concrete findings are: