The use of DNA probes for malaria diagnosis: memorandum from a WHO meeting.

Current progress in the development and potential application of DNA probes for malaria diagnosis was reviewed at an informal WHO Consultation in Geneva in October 1985. The development and use of such probes for malaria diagnosis is based on the premise that within any organism there are unique DNA sequences which differentiate that organism from closely related organisms. DNA probes specific for Plasmodium falciparum have been developed in several laboratories. Their major characteristic is that they are highly repeated within the P. falciparum genome. Their reported sensitivity in laboratory studies of from 5-10 pg to 1 ng DNA, which is equivalent to 10(2)-10(4) ring-stage parasites in a single sample, appears to be well within the range of that obtained by standard microscopical diagnosis. The technique, therefore, apparently has potential for operational use. A test based on use of the complete genome of P. falciparum has also been developed, and studies have recently been initiated on the diagnostic application of RNA probes and DNA probes specific for the human malaria parasites.Limited field evaluation of these probes indicates a sensitivity which compares well with that of traditional microscopy. However, this is based on the use of (32)P as a radioactive marker so that the test cannot be used in situations where there is no well-equipped laboratory. Attempts are, therefore, being made both to simplify the test and to develop non-radioactive methods for labelling the probes. The application of these techniques for malaria diagnosis within primary health care is discussed.