Stool Antigen Test Shows Higher Point Estimates Than Antibody Assay in Ghana Typhoid Study

Researchers in Cape Coast, Ghana, have compared two rapid diagnostic tests for typhoid fever against stool culture, the reference standard, in a group of 208 patients with clinically suspected disease. Their comparative cross-sectional study, published in BMC Infectious Diseases, found that a rapid stool antigen test produced higher point estimates for both sensitivity and specificity than the widely used serum antibody assay, although the differences between the two tests did not reach statistical significance. Typhoid fever remains a major public health challenge in low- and middle-income countries, where limited laboratory infrastructure often necessitates reliance on rapid diagnostic tests.

In Ghana, the serum antibody test is the most commonly used rapid option, but its reliability is limited. The study team enrolled 208 patients who presented with clinical suspicion of typhoid fever. Each participant provided stool and serum samples for parallel testing.

Stool samples were cultured to detect presumptive Salmonella isolates consistent with S. Typhi, and the same samples were tested with EvanCare rapid stool antigen kits. Serum samples were analysed with the JusChek Typhidot antibody test kit. The researchers then calculated how each rapid test performed against the stool culture results.

Stool culture identified 43 participants as positive and 165 as negative. Among the 43 culture-positive patients, the stool antigen test correctly detected 86.0 percent of infections, while the serum antibody test detected 76.7 percent. That difference of 9.3 percentage points came with a 95 percent confidence interval spanning from −6.62 to 24.92, and a p-value of 0.388, indicating the difference was not statistically significant.

Specificity, the ability to correctly identify people without the infection, told a similar story. Among the 165 culture-negative participants, the stool antigen test achieved 95.2 percent specificity compared with 90.3 percent for the serum antibody test, a difference of 4.9 percentage points. Again, the confidence interval of −0.25 to 10.33 and a p-value of 0.096 meant the researchers could not rule out that the apparent advantage was due to chance.

The researchers used McNemar’s test to assess paired differences in sensitivity and specificity, with corresponding 95 percent confidence intervals, and Cohen’s kappa to measure agreement between the two rapid tests. The authors concluded that although the point estimates favoured the stool antigen test on both sensitivity and specificity, the findings do not provide sufficient evidence to conclude that it is superior to the serum antibody assay.

The confidence intervals were wide, reflecting the modest number of culture-positive cases, and the p-values fell short of conventional significance thresholds on both measures. Nevertheless, the study offers practical information for resource-limited settings. The stool antigen test may provide a useful rapid diagnostic option where timely typhoid testing is required, since it performed reasonably well on both measures and can be run directly on stool samples.

The study’s cross-sectional design, single-site recruitment and sample size mean the results should be interpreted as preliminary evidence rather than definitive proof of superiority. For patients with suspected typhoid fever in Cape Coast, the practical message is that neither rapid test is perfect, and false results remain possible in both directions. Confirmatory culture remains important where feasible.

The study underscores a familiar tension in infectious disease diagnostics in low-resource settings: rapid tests offer speed and accessibility, but culture-based confirmation continues to set the benchmark against which all alternatives must be judged.

Subject of Research: Diagnostic performance of rapid stool antigen and serum antibody tests for typhoid fever compared with stool culture in Ghana

Article Title: Comparative performance of stool antigen and serum antibody assays relative to stool culture among patients with suspected typhoid fever in Cape Coast, Ghana

Article References: Cudjoe, O., Sidibe, F. I., Ansah, R. O., Nanor, J. D., Addo, N. N. N., Osei, R., Nyame, O. N., Donkor, A. B., Hagan, A. T., Ocansey, D. K. W., & Dadzie, I. (2026). Comparative performance of stool antigen and serum antibody assays relative to stool culture among patients with suspected typhoid fever in Cape Coast, Ghana. BMC Infectious Diseases. https://doi.org/10.1186/s12879-026-14398-w

Image Credits: AI Generated

DOI: 10.1186/s12879-026-14398-w

Keywords: typhoid fever, Salmonella Typhi, rapid diagnostic tests, stool antigen test, serum antibody assay, stool culture, diagnostic sensitivity, diagnostic specificity, Ghana, cross-sectional study, BMC Infectious Diseases, Comparative