Evaluation of the Widal tube agglutination test for the diagnosis of typhoid fever among children admitted to a rural hdospital in Tanzania and a comparison with previous studies

Abstract

Background: The diagnosis of typhoid fever is confirmed by culture of Salmonella enterica serotype Typhi (S. typhi). However, a more rapid, simpler, and cheaper diagnostic method would be very useful especially in developing countries. The Widal test is widely used in Africa but little information exists about its reliability.

Methods: We assessed the performance of the Widal tube agglutination test among febrile hospitalized Tanzanian children. We calculated the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of various anti-TH and -TO titers using culture-confirmed typhoid fever cases as the "true positives" and all other febrile children with blood culture negative for S. typhi as the "true negatives."

Results: We found that 16 (1%) of 1,680 children had culture-proven typhoid fever. A single anti-TH titer of 1:80 and higher was the optimal indicator of typhoid fever. This had a sensitivity of 75%, specificity of 98%, NPV of 100%, but PPV was only 26%. We compared our main findings with those from previous studies.

Conclusion: Among febrile hospitalized Tanzanian children with a low prevalence of typhoid fever, a Widal titer of > or = 1:80 performed well in terms of sensitivity, specificity, and NPV. However a test with improved PPV that is similarly easy to apply and cost-efficient is desirable.

Figure 1

Flow of patients. *Species included: Streptococcus pneumonia (n = 11), beta hemolytic Streptococci (n = 10), Staphylococcus aureus (n = 5), Haemophilus influenzae type b (n = 26), Escherichia coli (n = 31), Acinetobacter species (n = 6), Non-fermenters (n = 12), Others: (n = 5), Haemophilus parainfluenzae (n = 2), and Gram negative rods not identified (n = 5). **Species included: Bacillus (n = 22), Diphtheroids (n = 7), Micrococcus (n = 9), alpha-hemolytic Streptococcus viridans (n = 4), coagulase negative Staphylococcus (n = 104), yeast (n = 5), mixed bacterial species (n = 4), Gram positive rods not identified (n = 1).