Evaluation of Blood Culture, Widal Reaction, qPCR, and Immunochromatographic Test in the Diagnosis of Typhoid Fever and Its Co-Infection with Malaria among Hospitalized Febrile Patients in Lagos, Nigeria

Abstract

Background: Typhoid fever is endemic in Nigeria, and there are no high-quality routine diagnostic tests. Immunodiagnostic assays, blood culture, and quantitative real-time polymerase chain reaction (qPCR) were used to study typhoid fever co-infection with malaria. Materials & Methods: Blood samples of 125 patients were taken from April to August 2021. The samples were analyzed using standard microbiological methods such as immunodiagnostic assays and qPCR, whereas malaria parasitemia was examined using microscopy. Findings: In the study, the Widal test (WT) showed that 28.8 and 32.8% of the patients had antibodies against O-antigen and H-antigen at a cut-off titre of 1:160, respectively. The immunochromatographic test (ICT) indicated that 16% had IgM antibodies, and 18.4% had both IgM and IgG antibodies, suggesting a recent typhoid infection. Various bacterial pathogens were identified in patients with positive WT and ICT results, including Salmonella species, Klebsiella pneumoniae, Staphylococcus aureus, Streptococcus species, and Proteus mirabilis. Eight Salmonella strains were confirmed through invA gene detection using qPCR, none of which were S. Typhi and S. Paratyphi A. Both WT and ICT exhibited low sensitivity but high specificity ranging from 73.6 to 81.6% with negative predictive values of 100%. Additionally, the results showed a prevalence rate of 65.5% for malaria parasitemia and 9.8% for non-typhoidal Salmonella-associated bacteraemia co-infection with malaria. Conclusion: This research once again highlighted the limited diagnostic accuracy of both immunochromatographic and Widal tests. The presence of concurrent infections involving malaria and other bacterial pathogens further exacerbates the inadequacies of these diagnostic methods.