NIBSC - WHO endorses new International Standard for malaria diagnosis

A new international standard has been endorsed by the World Health Organization (WHO) to support detection of Plasmodium falciparum, the parasite responsible for most cases of human malaria.

The reference material will serve as a WHO International Standard (IS) for two P. falciparum proteins – histidine-rich protein 2 (HRP2) and Plasmodium lactate dehydrogenase (pLDH), common antigens used in malaria rapid diagnostic tests (RDTs).

Developed by scientists at NIBSC in collaboration with FIND, this new IS will support performance evaluation and quality control of existing and future malaria RDTs.

Testing before treatment

Back in 2012, WHO launched the ‘T3: Test. Treat. Track initiative’, supporting the global malaria community to strengthen malaria diagnosis, treatment and surveillance.

Accurate diagnosis, either by microscopy or use of RDTs, can improve quality of care and ensures appropriate use of anti-malarials. Because RDTs are cheap and accessible, they are widely used, with over 1.6 billion tests sold globally between 2010-2016. However, the performance of RDTs is variable, so there is a need for a consistent approach to controlling the quality and effectiveness of these tests.

As most RDTs work by detecting two specific P. falciparum proteins, HRP2 and pLDH, international reference materials to ensure the recognition of these proteins are an important tool for the evaluation of test sensitivity and quality and allow comparison between different diagnostic tests.

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Malaria Rapid Diagnostic Test. Image courtesy of CDC Global.

Current malaria reference materials used to calibrate RDTs and evaluate their performance and quality are made from frozen blood samples, which can make them difficult to prepare, characterise and transport.

About the standard

The lyophilised WHO IS preparation (NIBSC product code 16/376) for the evaluation of performance and sensitivity of malaria antigen detection tests has been established at 1000 International Units of the P. falciparum antigens HRP-2 and pLDH per ampoule.

Prepared using P. falciparum cell cultures, the standard will be used worldwide to assure the quality and harmonization of existing malaria detection tests and support the development of better, more sensitive RDTs in future.

A collaborative study involving 13 laboratories worldwide confirmed the suitability of this IS for the detection of HRP2 and pLDH using a variety of RDTs and enzyme-linked immunosorbent assays (ELISA).

Building confidence in diagnosis

"Our new WHO IS aims to address some of the challenges with malaria RDTs and adds to our growing collection of diagnostic malaria standards for P. falciparum"

Dr Paul Bowyer, Principal Scientist at NIBSC

Ensuring that rapid diagnostic tests are reliable and accurate is key for their continued use. Dr Paul Bowyer, Principal Scientist at NIBSC, comments:

"Rapid diagnostic tests are widely used to diagnose malaria, as they are easy to use, even in remote areas. However, the ongoing development of new tests and the variability in results and performance of existing ones means that steps need to be taken to make sure that those using them are confident in their accuracy and ability to correctly diagnose the condition."

"This new WHO IS aims to address some of these challenges and adds to our growing collection of diagnostic malaria standards for P. falciparum, including DNA and serum standards."

"Following the success of this project, we will continue to work with FIND to produce a portfolio of standards for Plasmodium vivax, the second most common malaria parasite, to support the diagnosis of this species as well."

This project was also supported by funding from the Bill & Melinda Gates Foundation, the UK and Australian Governments.

WHO endorses new International Standard for malaria diagnosis

Testing before treatment

About the standard

Building confidence in diagnosis

"Our new WHO IS aims to address some of the challenges with malaria RDTs and adds to our growing collection of diagnostic malaria standards for P. falciparum" Dr Paul Bowyer, Principal Scientist at NIBSC

"Our new WHO IS aims to address some of the challenges with malaria RDTs and adds to our growing collection of diagnostic malaria standards for P. falciparum"

Dr Paul Bowyer, Principal Scientist at NIBSC