Design of Rapid Malaria Tests Requires Improvement

Rapid diagnostic tests (RDT) for malaria, though simple and easy to use, are not correctly utilized or understood in less than perfect settings.

The RDT is used to diagnose malaria infections in tropical circumstances often by applying a drop of blood to a strip and waiting for some colored lines to appear, similar to the home pregnancy tests

Until recently treatment was initiated based on clinical suspicion, but a few years ago, the World Health Organization, (WHO, Geneva, Switzerland) advised to start treatment only after laboratory confirmation of the diagnosis. RDTs were thought to be the simple solution for diagnosing malaria infections, replacing the microscopic blood examination, which needed demanding tools, time, and expertise.

Scientists at the Institute of Tropical Medicine, (Antwerp, Belgium), tested the appropriateness of the RDTs in tropical settings. They found that existing tests for instance were not robust enough to differentiate between Plasmodium falciparum and P. vivax, a parasite from the subtropics, even if their label and even brand name suggested differently. Not all the tests reacted positively to high concentrations of parasites, as this overloading leads to a negative result or a very weak line, often read by inexperienced users as negative for malaria.

In the field, people sometimes replaced the liquid buffer in the test by tap water, or by the buffer of a different kit, because the flask was empty, or lost, or swapped, which led to false positives. The rapid tests also were not suitable to determine if treatment was successful. Some tests read positive up to weeks after the infection, even when in the mean time the infection was under control. The investigators found that some field workers suffered from presbyopia or farsightedness and needed reading glasses to conduct the test. The correct prescription spectacles were unavailable in many developing countries.

Philippe Gillet, PhD, who worked on the project, criticized the design and packaging of the RDTs. The instructions were in small print and in a complicated jargon, with unclear reading scales, and the pipettes were problematic to use. He said, " Not everything should be blamed on the manufacturers as all of it easily and cheaply to remediate. It already would make a large difference if the WHO and European Union would sharpen their rules for registration." When Dr. Gillet was in Belgium, Congo, Cuba, and Cambodia, he asked health workers about the international danger symbols on the products, less than half of them could give the right answers.

Related Links:
World Health Organization
Institute of Tropical Medicine