Evaluation in Papua New Guinea of a urine coagglutination test and a Widal slide agglutination test for rapid diagnosis of typhoid fever.

Two simple rapid tests for the laboratory diagnosis of typhoid fever were evaluated, a coagglutination test for detecting Salmonella typhi antigens in urine and a Widal slide agglutination for detecting serum antibodies. Ninety-two culture-confirmed typhoid cases were compared with 64 non-typhoid fever patients, 50 close contacts of typhoid patients, 30 vaccinated staff and 72 healthy community members. A strong urine Vi coagglutination was found to be 86.5% sensitive and 91.8% specific for typhoid, but was not always easy to read. The slide Widal H was found to be 99% sensitive and 95% specific whereas the slide Widal O was 98% sensitive and 98% specific. These data suggest that a single slide Widal O, at a reciprocal titre of 40, is the most suitable rapid test for the diagnosis of typhoid in a population with low typhoid antibody levels in the community, few other cross-reacting Salmonella infections, and a tendency for patients to present late in the infection.