Application of the passive haemagglutination test for malaria: the problem of false negatives.

In a study in a population in northern Tanzania, almost all adults and schoolchildren with parasitaemia were positive in the PHA test, whereas only half of the children under 5 years of age with parasitaemia were serologically positive. A second study on infants up to the age of 18 months confirmed that many young children who could be expected to have been exposed to malaria did not have PHA-detectable antibody.