Comparative Studies on the Diagnostic Validity of Widal and Evaluation of Interferon Gamma Response in Patients Investigated for Typhoid Fever

Abstract

Typhoid fever remains a public health challenge in developing countries. In Nigeria, patients usually come with complains of fever and other symptoms typical of febrile illnesses where resource limitation in healthcare facilities necessitates the use of screening tests for diagnosis. Widal test is widely used due to its simplicity. However, the specificity of this test has been debated. The present study compared the diagnostic validity of Widal to blood culture and evaluated interferon gamma response among the study participants. A total of 90 patients with complain of fever and other symptoms suggestive of typhoid fever were recruited for the study. Widal serology, automated blood culture and interferon gamma concentration were conducted using rapid antibody detection kit, BACTEC and sandwich enzyme linked immunosorbent assay (ELISA) respectively. Of the 90 samples tested, 63 (70.0%) were positive for anti Typhi O antigen while 42 (46.7%) were positive for anti- Typhi H antigen. Similarly, 18 (20%) of the patients had non-S. Typhi culture positivity while 72 (80%) had no bacteria isolated. Overall, 0 (0%) of the cases had S. Typhi positive culture. Fisher’s exact test suggests a significant difference between blood culture status and prevalence of anti-S. Typhi H antigen. Interferon gamma concentration was found to be significantly associated with blood culture status as plasma interferon gamma levels increased with bacteraemia. Fisher’s exact test showed a strong statistical relationship between interferon gamma concentration and blood culture (p=0.003). Interferon gamma has a direct proportionality with non- S. Typhi culture as such, could be a good marker for the development of an alternative screening test, possibly an interferon gamma based detection system for typhoid fever. However, further research is required to implement that.