Field application to malaria studies of the passive haemagglutination (PHA) test with lyophilized cells.

Lyophilized cells for the passive (formerly indirect) haemagglutination test for malaria were tested in a small field trial. A comparison was made with results obtained with samples from the same persons by another method in another laboratory (Center for Disease Control, Atlanta, GA, USA). The use of lyophilized cells of standardized reactivity clearly adds to the simplicity and rapidity of the test, and justifies its recommendation for use in field studies.