WHO/BS/2017.2329 Collaborative study to evaluate the proposed 1st WHO IS for Plasmodium falciparum antigens

Overview

An international collaborative study was conducted to assess the suitability of a candidate IS in vitro-derived Plasmodium falciparum preparation, assigned product code 16/376, for use as a World Health Organization (WHO) International Standard (IS) in the detection of P. falciparum antigens histidine-rich protein 2 (HRP-2) and plasmodial lactate dehydrogenase (pLDH). The potencies of the candidate IS and a range of P. falciparum clinical isolates were evaluated using commercially available Enzyme-linked immunosorbent assays (ELISA) and a wide variety of malaria rapid diagnostic tests (RDT).

The samples for evaluation were distributed to 13 laboratories in 11 different countries. Five participating laboratories carried out ELISAs and all participants performed RDTs. The samples were assayed on four separate days and the data were collated and analysed by the National Institute of Biological Standards and Control (NIBSC). The results demonstrated that HRP2 and pLDH were detected consistently in samples by the majority of participants. The candidate IS is stable under recommended storage conditions of -70 ℃ or below, and therefore suitable for long term use. Real-time and accelerated stability studies of the candidate IS are ongoing.

It is proposed that the lyophilised P. falciparum candidate IS preparation 16/376 be established as the 1st WHO IS for P. falciparum antigens with 1000 International Units per ampoule for the evaluation of performance and sensitivity of malaria antigen detection tests.