Evaluation of salivary anti-Salmonella typhi lipopolysaccharide IgA ELISA for serodiagnosis of typhoid fever in children.

This observational study was conducted to determine the diagnostic accuracy of ELISA for the detection of anti-Salmonella typhi lipopolysaccharide (LPS) salivary immunoglobulin A (IgA) antibodies in 37 children with culture confirmed typhoid, 30 febrile controls with an alternative diagnosis and 30 healthy controls. The test was positive in 33/37 (89.2%) cases of typhoid, but negative in all patients in the two control groups. Maximum absorbance of anti-LPS IgA was observed during the second and third weeks of typhoid, with a progressive decline thereafter. The sensitivity of ELISA was 71.4%, 100%, 100%, 9.1% and 0%, in first, second, third, fourth and fifth week of illness, respectively. Further large scale studies measuring salivary anti-LPS IgA antibodies are needed to confirm the potential of saliva-based serology in children with suspected typhoid.