Typhidot M and Diazo test vis-à-vis blood culture and Widal test in the early diagnosis of typhoid fever in children in a resource poor setting

Abstract

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% of the cases. Among these culture positive cases, typhidot M test had the highest sensitivity, specificity, PPV and NPV of 90% (95% CI = 74.4-96.5), 100% (95% CI = 90.1-100), 100% (95% CI = 87.5-100), and 92.1% (95% CI = 79.2-97.3) respectively. Diazo test ranked next with sensitivity, specificity, PPV and NPV of 86.7% (95% CI = 70.3-94.7), 85.7% (95% CI = 70.6-93.7), 83.9% (95% CI = 67.4-92.9), 88.2% (95% CI = 73.4-95.3) respectively. Among clinically suspected typhoid cases, the overall sensitivity, of blood culture, Widal, typhidot M, Diazo was 27.3% (95% CI = 19.8- 36.3), 64.6% (95% CI = 55.3-72.9), 89.1% (95% CI = 81.9-93.7), 80.9% (95% CI = 72.6-87.2) respectively. In the first week of illness, typhidot M showed the best sensitivity [86.2% (95% CI = 69.4-94.5)] followed by Diazo [79% (95% CI = 61.6-90.2)], Widal [41.4% (95% CI = 25.5-59.3)] and blood culture [31% (95% 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.