The role of the laboratory in the diagnosis and management of typhoid fever.

In typhoid-endemic areas the results obtained from the laboratory are important in confirming the clinical diagnosis of typhoid and may also contribute to decisions made on the management and treatment of typhoid cases. Isolation of Salmonella typhi remains the gold standard, with culture from bone marrow aspirate or a combination of specimens from other body sites resulting in the greatest sensitivity. Antibody detection techniques may still provide valuable information, but only if the results are interpreted in the context of the background antibody levels in the local population. None of the available antigen detection techniques have been consistently demonstrated to be of diagnostic value and a recently developed polymerase chain reaction (PCR) for the detection of Salmonella typhi has yet to undergo a full-scale clinical evaluation. The initial identification of chronic typhoid carriers relies upon the detection of elevated Vi capsular antibody levels, but seeking out chronic carriers will be of limited value in controlling the spread of typhoid in areas where transmission is principally mediated by convalescent excretors. Whilst resistance of Salmonella typhi to antibiotics has emerged as an increasing problem in some areas of the world, it is still uncommon in isolates from Papua New Guinea. However, monitoring of antibiotic susceptibility patterns will ensure that signs of developing resistance are detected early and that the appropriate action is taken.