Upping the Detection Power of Malaria Tests
Many countries that have implemented successful malaria control programs are now close to achieving the goal of elimination. According to the 2017 World Malaria Report, the World Health Organization identified 21 countries in 2016 with the potential to eliminate the disease by 2020.
However, in areas where malaria prevalence has decreased, a significant portion of infected individuals may have low-density parasite infections with few symptoms. These low-density cases can still transmit infection. The challenge is in identifying such cases, which are not readily detected using traditional rapid diagnostic tests (RDTs) and standard microscopy. The next generation of diagnostics for malaria must be sensitive enough to detect low-density cases at the point of care so that patients can be treated, and the cycle of transmission broken.
New Sensitive Tests are Now Available
To address this need, PATH and our partners are advancing more sensitive diagnostic tests to support malaria elimination. PATH has supported a number of companies developing next-generation malaria diagnostics through technical assistance and independent evaluations.
The first highly sensitive malaria diagnostic was launched in April 2017. The Alere™ Malaria Ag P.f is an in vitro, qualitative, and highly sensitive test developed by Abbott to aid in the diagnosis of Plasmodium falciparum malaria infection. It has a greater than ten-fold improvement in detection of the histidine-rich protein 2 (HRP2) antigen of P. falciparum malaria in human whole blood over currently available RDTs, which enables better identification of individuals with very low-density infections. Abbott’s Alere™ Malaria Ag P.f is fast, portable, easy to use, and provides quick and accurate results. This diagnostic is a more scalable option as compared to molecular assays that require expensive and complex laboratory equipment. It may help health care workers in rural and remote areas to screen for low-density infections.
Also launched in 2017 was a new enzyme-linked immunosorbent assay (ELISA) laboratory test for P. falciparum, the Alere™ Malaria Ag P.f HRP2 ELISA. This ELISA can serve as a laboratory confirmation test when used in combination with highly sensitive rapid tests for malaria. The ELISA represents a several-fold improvement over other ELISAs without adding complexity or cost to end-user laboratories. Previously, ELISA kits and protocols for malaria were not standardized, so results could not be accurately compared across laboratories and countries. This new ELISA includes a standardized method and components needed to conduct the test, including appropriate controls, which enables fast and efficient processing of specimens and ensures comparability of results.
Two New, More Sensitive Diagnostic Tools for Malaria are Now Available.
The Alere™ Malaria Ag P.f is a highly sensitive rapid diagnostic test that is ten times more sensitive than existing rapid tests, capable of detecting very faint traces of P. falciparum malaria parasites in the blood. The Alere™ Malaria Ag P.f HRP2 ELISA is a laboratory confirmation test that improves on other ELISAs without adding complexity or cost to end-user laboratories.
The Future of Malaria Diagnostics
More sensitive tests for malaria are on the horizon. To facilitate the development of new malaria diagnostics, PATH and Precision Antibody collaborated to develop and bring to market custom monoclonal antibodies to HRP2. These antibodies are a new and robust asset that can be used by RDT manufacturers to develop next-generation tests for malaria. To determine the target performance characteristics of new malaria tests, PATH is researching biomarkers for P. falciparum and Plasmodium vivax infections, including lactate dehydrogenase and parasite nucleic acids. In this capacity, PATH is working with diagnostic manufacturers to develop a multiplexed quantitative malaria antigen detection platform that will allow the malaria community to better understand the performance of malaria RDTs. PATH is also evaluating tests that address HRP2 and HRP3 deletions in P. falciparum malaria parasites, which are increasingly the cause of false negatives using HRP2 RDTs. These developments may pave the way for a sensitive test to better serve the malaria community to improve patient care and achieve malaria elimination.