Malaria RDTs are designed predominantly for use in malaria endemic areas beyond the reach of good quality microscopy. The ultimate test of their performance is therefore accuracy attained in such an environment, after enduring probable conditions of transport and storage, in the hands of the intended end-users, in high-quality field trials. Performance in such conditions may be affected by the quality of manufacture and packaging, exposure to high temperatures, preparation and interpretation by the end-user, and characteristics of the host population and parasites in the area where they are used.
Requirements and Limitations of Field Trials
Field trials are useful in confirming that high levels of performance observed in the laboratory is maintained in the field, and in investigating certain aspects of RDT use such as ease of use and safety, or outcomes in populations with specific characteristics. Good field trails are relatively expensive to implement, and are unsuited to comparison of many RDTs as it is logistically difficult to test many RDTs in parallel in their intended conditions of use, and variation within the study population makes testing in series inappropriate.
Field trials of malaria RDTs are further limited by the requirement for a reference standard that is clearly better performing than the expected performance of the RDT under evaluation. This is difficult to achieve with light microscopy, as RDTs may potentially out-perform microscopy in some aspects of parasite detection. The use of more sensitive methods such as PCR is usually necessary to obtain reliable estimates of sensitivity and specificity.
In order to allow comparison of results between various field trials, it is essential that field trials of malaria RDTs are planned, performed and documented meticulously according to the standards necessary for comparative trials of any diagnostic method. Without strict adherence to standardized protocols and clear documentation of conditions and standards used, it is difficult or impossible to draw firm conclusions from results. Poorly designed or documented trials will have, or should have, little impact on implementation policy. Well planned, performed, and documented trials can be of major benefit to public health.