A comparative study of Widal test and Typhidot (IgM and IgG specific assay) test in the diagnosis of enteric fever

Background: Enteric fever (Typhoid fever) is a common systemic infectious disease worldwide, especially in developing countries like India and continues to be one of the leading causes of morbidity and mortality. It is caused by the bacterium Salmonella typhi or Salmonella paratyphi serotypes A, B and C. The clinical diagnosis of Enteric fever traditionally depends on Blood culture and Widal tests. However limitations such as longer time for Blood culture results and difficulties in the interpretation of Widal tests make them unpractical for screening patients in endemic regions and lead to misdiagnosis and missed diagnosis. Aim and objectives: Purpose of the study was to compare the sensitivity and specificity of Widal test and Typhidot based IgM and IgG assay with the Blood culture (taken as gold standard) in the diagnosis of Enteric fever. Materials and methods: This comparative study was done on 120 patients in the General Medicine Department of Indira Gandhi Institute of Medical Sciences, Patna. All patients above 11 years of age of either sex with acute febrile illness suspected to have Enteric fever were included in this study. Febrile patients with other diagnosis were excluded. Blood culture, Widal test, Typhidot (IgM and IgG) test and other routine investigations were performed in all patients. Typhidot tests and Widal tests were compared for sensitivity and specificity. Results: Out of 120 clinically diagnosed cases of Enteric fever, 18(15%) patients were Blood culture positive for Salmonella typhi, 27(22.5%) patients were positive on Widal tests and 36(30%) were Typhidot positive. Out of 18 Blood culture positive patients for Salmonella typhi, 10 patients were positive and 8 were negative on Widal testing. Out of 36 Typhidot positive patients 16 patients were positive and 20 were negative on Blood culture. Conclusions: Traditionally Blood culture and Widal test are used in the diagnosis of Enteric fever. However Typhidot (IgM & IgG assay) tests are simple and rapid screening tests that simultaneously detect and differentiate between IgM and IgG antibody to Salmonella typhi and paratyphi produced in response to infection, thus aiding in determination of current or previous exposure. It offers the advantage of early and rapid diagnosis and helps in early institution of therapy. Preliminary data have shown sensitivity and specificity of 95% and 86% respectively of Typhidot tests.