Abstract
BackgroundSalmonella enterica serovar Typhi, the causative agent of typhoid, is endemic in most parts of the world especially in Africa. Reliable and rapid diagnosis of the bacterium is therefore critical for confirmation of all suspected typhoid cases. In many parts of Zimbabwe, laboratory capacity to isolate the microorganism by culture method as a way of diagnosis has limitations. In this study, two rapid serological kits, TUBEX-TF and OnSite Typhoid IgG/IgM Combo, were evaluated for possible expeditious diagnosis of Salmonella enterica serovar Typhi infection during a typhoid outbreak in Zimbabwe.MethodsBlood was collected from patients with clinical signs and symptoms of typhoid in Harare, Zimbabwe during an outbreak. The standard culture method was used to diagnose the disease. Two rapid kits, the TUBEX-TF and OnSite Typhoid IgG/IgM Combo, were also used in parallel to diagnose typhoid according to manufacturers’ instructions. The diagnostic accuracy of the two kits was evaluated using the culture method as the gold standard.ResultsFrom all the cases diagnosed by the blood culture (n = 136), we enrolled 131 patients for the TUBEX-TF and 136 for the OnSite Typhoid IgG/IgM Combo tests. With the culture method as a reference standard, we found that TUBEX-TF test was 100% sensitive and 94.12% specific, with 63.16% positive and 100% negative predictive values (NPVs) and the OnSite Typhoid IgG/IgM Combo test was 100% sensitive and 94.35% specific, with 63.16% positive and 100% NPVs.ConclusionOur results indicated that TUBEX-TF and OnSite Typhoid IgG/IgM Combo rapid tests were useful tools for the rapid diagnosis of Salmonella enterica serovar Typhi infection during typhoid outbreaks in Zimbabwe. The tests performed very well in laboratory evaluations of blood culture-confirmed typhoid cases in Harare, Zimbabwe.
Highlights
Salmonella enterica serovar Typhi, the causative agent of typhoid, is endemic in most parts of the world especially in Africa
Typhoid fever is an important acute disease that is caused by Salmonella enterica serovar Typhi infection [1]
Serological tests such as hemagglutination test and enzyme-linked immunosorbent assay (ELISA) have been used to diagnose Salmonella enterica serovar Typhi infection, but they are limited in specificity and sensitivity [6]
Summary
Salmonella enterica serovar Typhi, the causative agent of typhoid, is endemic in most parts of the world especially in Africa. All other test methods are normally evaluated against the culture method to ensure their appropriateness, efficiency and effectiveness Serological tests such as hemagglutination test and enzyme-linked immunosorbent assay (ELISA) have been used to diagnose Salmonella enterica serovar Typhi infection, but they are limited in specificity and sensitivity [6]. Commercial rapid antibody tests that detect the presence of Salmonella enterica serovar Typhi antigens/antibodies have been made available in recent years and are used in early outbreak detection, patient management and surveillance [1,8] They can potentially be used as point-of-care (POC) tests and they are rapid and user-friendly. The objective of this study was to evaluate two commercially available rapid diagnostic kits, the TUBEX-TF and the OnSite Typhoid IgG/IgM Combo for the laboratory detection of Salmonella enterica serovar Typhi infection in Zimbabwe
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