Abstract
Typhoid fever, also known as typhoid, is a life-threatening bacterial infection that remains a global health concern. The infection is associated with a significant morbidity and mortality rate, resulting in an urgent need for specific and rapid detection tests to aid prevention and management of the disease. The present review aims to assess the specificity and sensitivity of the available literature on the immunodiagnostics of typhoid fever. A literature search was conducted using three databases (PubMed, ProQuest and Scopus) and manual searches through the references of identified full texts to retrieve relevant literature published between 1 January 2011 and 31 December 2020. Of the 577 studies identified in our search, 12 were included in further analysis. Lipopolysaccharides (LPS) and hemolysin E (HlyE) were the most frequently studied antigens. The specimens examined in these studies included serum and saliva. Using blood culture as the gold standard, anti-LPS IgA gave the highest sensitivity of 96% (95% CI: 93–99) and specificity of 96% (95% CI: 93–99) for distinguishing between typhoid cases and healthy controls, whereas the combination of anti-LPS and anti-flagellin total IgGAM gave the highest sensitivity of 93% (95% CI: 86–99) and specificity of 95% (95% CI: 89–100) for distinguishing typhoid cases and other febrile infections. A comparably high sensitivity of 92% (95% CI: 86–98) and specificity of 89% (95% CI: 78–100) were shown in testing based on detection of the combination of anti-LPS (IgA and IgM) and anti-HlyE IgG as well as a slightly lower sensitivity of 91% (95% CI: 74–100) in the case of anti-50kDa IgA. Anti-50kDa IgM had the lowest sensitivity of 36% (95% CI: 6–65) against both healthy and febrile controls. The development of a rapid diagnostic test targeting antibodies against lipopolysaccharides combined with flagellin appeared to be a suitable approach for the rapid detection test of typhoid fever. Saliva is added benefit for rapid typhoid diagnosis since it is less invasive. As a result, further studies could be done to develop additional approaches for adopting such samples.
Highlights
Typhoid fever is a systemic infection associated with the Gram-negative and rodshaped bacillus Salmonella enterica serovar Typhi
The anti-LPS IgA gave the highest sensitivity of 96%, followed by antiLPS (IgA and IgM), which achieved a sensitivity of 95%, anti-LPS IgM6 of 14 with 94% and anti-hemolysin E (HlyE) IgA with 94%
The present systematic review sought to evaluate the performance of newly developed immunodiagnostic tests for typhoid fever reported in the past 10 years to identify an alternative option for accurate laboratory testing
Summary
There is a declining global trend in typhoid incidence over the last few years with respect to the number of cases per capita, in most high-income countries, such as Australia, Japan, New Zealand, Singapore, South Korea and Taiwan and middle-income countries, such as Malaysia and Thailand [2]. In some countries such as Ghana, Malawi, Fiji, China, Indonesia, Cambodia and Iraq, typhoid incidence shows a steady increase from 1990 to 2014. These numbers are more than likely an underrepresentation of the true disease burden given that a large proportion of patients are treated on an outpatient basis or receive no treatment at all. Typhi infection per 100,000 population were reported each year between 2011 and 2015 and most of the cases were due to travelers returning from an endemic region, migrants and food chains being contaminated by food handlers [3]
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