Update on rapid diagnostic testing for malaria

Abstract

To help mitigate the expanding global impact of malaria, with its associated increasing drug resistance, implementation of prompt and accurate diagnosis is needed. Malaria is diagnosed predominantly by using clinical criteria, with microscopy as the current gold standard for detecting parasitemia, even though it is clearly inadequate in many health care settings. Rapid diagnostic tests (RDTs) have been recognized as an ideal method for diagnosing infectious diseases, including malaria, in recent years. There have been a number of RDTs developed and evaluated widely for malaria diagnosis, but a number of issues related to these products have arisen. This review highlights RDTs, including challenges in assessing their performance, internationally available RDTs, their effectiveness in various health care settings, and the selection of RDTs for different health care systems.

FIG. 1.

Schematic of an MRDT. On one end of the nitrocellulose strip, one or two indicator-labeled antibodies, one specific for each target antigen, are placed. A second antibody specific for a different epitope of each of the target antigens is bound to the strip in a thin line. Another antibody specific for the indicator-labeled antibody complex is bound at the control line. Blood and buffer are added to the strip where the lysing agent and labeled antibody are located and are drawn up the strip. If antigen is present, some indicator-labeled antibody-antigen complexes will be trapped on the test line and become visible. Additional indicator-labeled antibody is trapped on the control line and becomes visible.

FIG. 2.

Example of the only U.S. FDA-approved MRDT product, BinaxNOW Malaria (Binax, Inc., Inverness Medical Professional Diagnostics, Scarborough, ME (note that the package design has changed from the pictured version)). This assay is based on detection of the antigens HRP-2 (for P. falciparum) and aldolase (for generic Plasmodium). Per the package insert, the overall sensitivity and specificity are 95.3% and 94.2%, respectively, for P. falciparum, and 68.9% and 99.8%, respectively, for P. vivax. (Top) Card undergoing sample wicking up the nitrocellulose strip after application of the blood and reagent. (Bottom) Example of two cards. The left card has a positive control line and a positive generic Plasmodium line, while the right card has a positive control line, a positive P. falciparum line, and a positive generic Plasmodium line.