Comparative study of Widal test against stool culture for typhoid fever suspected cases in southern Ethiopia

Abstract

Introduction:

Infection caused by Salmonella enterica subsp. serotype Typhi remains an important public health problem in developing countries. Culture is an effective diagnostic method of confirming this infection. Diagnosis in developing countries is mostly done by Widal test, which is nonreliable. The aim of this study was to compare the Widal test against stool culture in typhoid-suspected cases and to evaluate the agreement between test methods.

Methodology:

A cross-sectional study design was conducted on typhoid-suspected cases in southern Ethiopia. Collected data were entered into Epi-Info version 3.5.1 and exported to SPSS version 20.0 for further analysis. Kappa test was used to assess the agreement between the tests. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were calculated to compare the Widal test against stool culture.

Results:

A total of 95 patients participated in the study, of whom 49 (51.6%) were females and 46 (48.4%) were males. The age range of the suspected cases were between 10 and 62 years, with mean age of 27.9 years. Of the examined cases, 65 (68.4%) were positive for slide agglutination Widal test, whereas only 19 (20.0%) were positive for S. enterica serotype Typhi by stool culture. The sensitivity, specificity, PPV, and NPV of slide agglutination test against stool culture were 84.2%, 35.5%, 24.6%, and 90.0%, respectively. Slide agglutination test has a poor agreement with the stool culture (kappa = 0.103), but tube titration test has a fair agreement with the stool culture (kappa = 0.325).

Conclusion:

Widal test has a low specificity and PPV but has better sensitivity and NPV than a stool culture. It also has a poor agreement with the stool culture. Therefore, physicians should not be totally dependent on the Widal test in endemic areas and in areas where it is the only diagnostic method for typhoid fever.

Keywords::

• typhoid fever
• Widal slide agglutination test
• Widal tube titration test
• stool culture

Acknowledgments

The authors are grateful to Arba Minch General Hospital for permission for data collection and the hospital laboratory staff for their assistance during data collection. The authors also wish to thank assistant professor Tsegaye Tsalla for his constructive advice in the study.

Author contributions

GA: participated in the design of the study, monitored data collection, analyzed the data, and drafted the manuscript. EA, BK, and BY: conducted data collections, participated in the design of the study, and participated in drafting of the manuscript. All the authors have read and approved the final manuscript.

Disclosure

The authors report no conflicts of interest in this work.