WHO is collaborating in development of stable, well-calibrated positive control wells containing recombinant antigens and designed to allow testing of malaria RDTs at clinic or village levels. These positive control wells will enable rapid direct evaluation of RDTs performance in remote locations without the need for cross-checking against expert microscopy. Such testing has the potential to increase the confidence of clinicians in the quality of RDTs after transport to remote areas or prolonged storage, allowing them to confidently manage symptoms according the RDT result.
The specifications for the development of the wells include:
- Good stability in ambient conditions in malaria-endemic areas
- Low cost (equivalent to an RDT)
- Ease of use, with no additional required chemicals or reagents (reconstitution with clean water)
- Similar viscosity to blood once reconstituted
- Recombinant proteins of all three common target antigens of P. falciparum (HRP2, pLDH, and aldolase)
- Antigen concentration equivalent to a typical parasite sample at 200 parasite/microL (determined from antigen concentrations of the malaria specimen bank).
WHO and FIND plan large scale implementation trials of positive control wells for 2011.
A panel of wells of containing different target antigens, and variants of antigens, is also under development for standardized testing to be carried out at national level, which could have application for national regulatory testing and pre- or post-purchase lot-testing.