Résumé
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 Jyoti Kumar Dinkar, Naresh Kumar, Chandrakishore. A comparative study of Widal test and Typhidot (IgM and IgG specific assay) test in the diagnosis of enteric fever. IAIM, 2017; 4(7): 126-130. Page 127 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.
Résumé
OBJECTIVE: Typhoid fever is a major public health problem. A test which is simple, reliable and can be carried out in small laboratories is the need of the hour. We prospectively evaluated typhidot M and Diazo tests vis-à-vis blood culture and Widal test in children. METHODS: Patients aged 6 months to 12 years, having fever of more than four days duration with clinical suspicion of typhoid fever were enrolled. Patients in whom other diagnosis was made served as control. The tests under scrutiny were validated against blood culture and then all the four tests were evaluated among patients who presented in the first week of illness. RESULTS: Blood culture was positive in only 27.3 percent of the cases. Among these culture positive cases, typhidot M test had the highest sensitivity, specificity, PPV and NPV of 90 percent (95 percent CI = 74.4-96.5), 100 percent (95 percent CI = 90.1-100), 100 percent (95 percent CI = 87.5-100), and 92.1 percent (95 percent CI = 79.2-97.3) respectively. Diazo test ranked next with sensitivity, specificity, PPV and NPV of 86.7 percent (95 percent CI = 70.3-94.7), 85.7 percent (95 percent CI = 70.6-93.7), 83.9 percent (95 percent CI = 67.4-92.9), 88.2 percent (95 percent CI = 73.4-95.3) respectively. Among clinically suspected typhoid cases, the overall sensitivity, of blood culture, Widal, typhidot M, Diazo was 27.3 percent (95 percent CI = 19.8- 36.3), 64.6 percent (95 percent CI = 55.3-72.9), 89.1 percent (95 percent CI = 81.9-93.7), 80.9 percent (95 percent CI = 72.6-87.2) respectively. In the first week of illness, typhidot M showed the best sensitivity [86.2 percent (95 percent CI = 69.4-94.5)] followed by Diazo [79 percent (95 percent CI = 61.6-90.2)], Widal [41.4 percent (95 percent CI = 25.5-59.3)] and blood culture [31 percent (95 percent CI = 17.3-49.2)]. CONCLUSION: Both Typhidot M and Diazo are good screening tests for the diagnosis of typhoid fever. Typhidot M is superior to Diazo but the latter is more suitable to resource poor settings being economic and easy to perform.