Evaluation of the Performance of Widal Slide Agglutination Test Compared to Blood Culture and Evaluation of Interferon Gamma Response in the Diagnosis of Typhoid Fever

Abstract

Typhoid fever remains a public health challenge in developing countries including Nigeria. Widal test is widely used for the diagnosis of typhoid fever due to its simplicity and short turnaround time. However, the specificity of this test has been debated. The aim of the study was to evaluate the performance of Widal test compared to blood culture and determine interferon gamma response among the study subjects. Blood samples were collected from 90 patients who complained of fever and other symptoms suggestive of typhoid fever. Widal slide agglutination test, automated blood culture and interferon gamma concentrations 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 blood samples were non- S. Typhi culture positive while 72 (80%) had no bacteria isolated. None of the cases had S. Typhi positive culture. With regards to interferon gamma, subjects with lower levels of 15pg/mL had no bacteria isolated from their blood. As the interferon gamma concentration increased, more subjects had non- S. Typhi bacteria isolated from their blood which shows the relationship between interferon gamma and bacteraemia. The study demonstrated that the use of Widal serology test in the diagnosis of typhoid fever may be erroneous as all the samples were found to be negative for S. Typhi using the gold standard culture methods while Interferon gamma concentration was statistically related to the isolation of non- S. Typhi in blood 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 recommended to elucidate that.