Assessing reliability of Widal test for typhoid fever case detection amongst outpatients attending two hospitals in Kano State, Nigeria

Abstract

Background: Typhoid or enteric fever is caused by Salmonella typhi that cause salmonella food poisoning is acquired by ingesting food or water contaminated with faeces of infected humans or animals. The bacteria multiply and spread from intestines into the blood stream affecting many organs.

Aim: This study was to assess the Salmonella typhi infection prevalence among outpatients attending two hospitals in Kano State. Secondly, to compare the reliability of Widal test with the blood and stool culture for isolating S. typhi regarded as “gold standard”. Thirdly, determine the co-occurrence of typhoid fever infection with anaemia.

Methodology: The sample population (n=200) comprised children (n=118) 3-9 years old and adults (n=82) were screened for typhoid fever. The highest serum dilution with agglutination was taken as positive antibody titre. The blood samples were inoculated into thioglycolate agar for seven days and thereafter sub-cultured in Mac Conkey agar for 18 - 24 hours at 37ºC. Pale yellow to near colourless colonies were identified as Salmonella spp. Anaemia was assessed using blood pack cell volume (PCV).

Results: Overall, the Widal test prevalence rate was 89 (44.5%) with male (n=123) having 50 (40.1%) and females (n=87) with 39 (30.7%). There was significant difference (p < 0.05) between Salmonella species isolated from males, 38 (30.9%) and females, 27 (35.1%), and no significant difference between the Widal test kit with 44 (44.0%) and 45 (45%) prevalence with 32 (72.72%) and 33 (73.33%) isolates, respectively. Among the Widal test positive (n=44), 16 (36.4%) had PCV below 30%.

Conclusion: This study had shown that Widal test is not definitive and incapable of differentiating active from past exposure to infection compared to isolating S. typhi in culture media. Sole reliance on Widal test for case detection and management should be done with caution considering the clinical prognosis of bacteraemia and anaemia may lead to death.