Comparison of Blood Culture and Single Slide Agglutination Widal Test for the Diagnosis of Enteric Fever

Abstract

Introduction: Enteric fever is a leading cause of mortality and morbidity in the developing world. Unawareness of public concerning the sanitation & hygiene led to the high prevalence of the disease.

Methods: Blood sample of patients suspecting enteric fever attending STIDH of all age group were collected & simultaneously data on pre-disposing factors associated with systemic febrile illness were collected according to the questionnaire designated. The collected blood samples were brought immediately to the laboratory. Upon arrival, the blood samples were processed for blood culture and single slide agglutination Widal test according to the standard laboratory methods.

Results: Of the total 237 cases, 13 (5.48%) were confirmed as enteric fever by blood culture with 5 (38.46%) Salmonella enterica serovar Typhi and 8 (61.54%) Salmonella enterica serovar Paratyphi A. Out of the total cases, 7 (2.95%) were positive for blood culture as well as Widal test.

At the serum titre of 1:80, Widal test showed the sensitivity of 28.57% and specificity of 73.56% for O antigen whereas sensitivity of 71.42% and specificity of 61.36% for H antigen. PPVs for the test were quite low with 8% for O antigen, 12.82% for H antigen and 12.5% for AH antigen. NPVs were 92.75% for O antigen, 96.42% for H antigen and 95.08% for AH antigen. Most of the culture confirmed cases, 9 (69.23%) were positive in the 1^st week of onset of fever and most of the widal positive cases, 49(51.57%) were positive in the 2^nd week of onset of fever.

Conclusion: Single slide Widal test of titre value ≥ 1:160 was found to be useful tool for diagnosis of enteric fever but the results should be corelated with clinical findings.