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Multicenter Study
. 2022 Dec 21;60(12):e0100022.
doi: 10.1128/jcm.01000-22. Epub 2022 Nov 30.

Comparative Analysis of Commercially Available Typhoid Point-of-Care Tests: Results of a Prospective and Hybrid Retrospective Multicenter Diagnostic Accuracy Study in Kenya and Pakistan

Jyotshna Sapkota  1   2   3 , Rumina Hasan  4   5 , Robert Onsare  6 , Sonia Arafah  1 , Sam Kariuki  6 , Sadia Shakoor  4 , Farah Qamar  4 , Sheillah Mundalo  6 , Frida Njeru  6 , Rael Too  6 , Elizabeth Ndegwa  6 , Jason R Andrews  7 , Sabine Dittrich  1   8
Affiliations
Multicenter Study

Comparative Analysis of Commercially Available Typhoid Point-of-Care Tests: Results of a Prospective and Hybrid Retrospective Multicenter Diagnostic Accuracy Study in Kenya and Pakistan

Jyotshna Sapkota et al. J Clin Microbiol. .

Abstract

Blood and bone marrow cultures are considered the gold standard for the diagnosis of typhoid, but these methods require infrastructure and skilled staff that are not always available in low- and middle-income countries where typhoid is endemic. The objective of the study is to evaluate the sensitivity and specificity of nine commercially available Salmonella Typhi rapid diagnostic tests (RDTs) using blood culture as a reference standard in a multicenter study. This was a prospective and retrospective multicenter diagnostic accuracy study conducted in two geographically distant areas where typhoid is endemic (Pakistan and Kenya; NCT04801602). Nine RDTs were evaluated, including the Widal test. Point estimates for sensitivity and specificity were calculated using the Wilson method. Latent class analyses were performed using R to address the imperfect gold standard. A total of 531 serum samples were evaluated (264 blood culture positive; 267 blood culture negative). The sensitivity of RDTs varied widely (range, 0 to 78.8%), with the best overall performance shown by Enterocheck WB (72.7% sensitivity, 86.5% specificity). In latent class modeling, CTK IgG was found to have the highest sensitivity (79.1%), while the highest overall accuracy was observed with Enterocheck (73.8% sensitivity, 94.5% specificity). All commercially available Salmonella Typhi RDTs evaluated in the study had sensitivity and specificity values that fell below the required levels to be recommended for an accurate diagnosis. There were minimal differences in RDT performances between regions of endemicity. These findings highlight the clear need for new and more-accurate Salmonella Typhi tests.

Keywords: Salmonella Typhi; blood culture; point-of-care tests; rapid diagnostic tests; typhoid.

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Conflict of interest statement

The authors declare a conflict of interest. J.S., S.A., and S.D. were employees of FIND at the time of the study. J.R.A. has received funding from the US National Institutes of Health and Bill and Melinda Gates Foundation. J.S., R.O., R.H., S.K., S.S., F.Q., S.M., F.N., R.T., and E.N. declare that they have no competing interests relevant to this work.

Figures

FIG 1
FIG 1
Patient disposition. RDT, S. Typhi rapid diagnostic test.
FIG 2
FIG 2
Sensitivity and specificity of nine S. Typhi RDTs (mITT population) assessed using blood culture testing to confirm diagnosis. CI, confidence interval (Wilson method); IgG, immunoglobulin G; IgM, immunoglobulin M; mITT, modified intent-to-test; RDT, rapid diagnostic test. Note that Diaquick S. Typhi IgG/IgM Ab tests are not done in the subjects of retrospective samples.
FIG 3
FIG 3
Comparison of Widal test with two best performing RDTs. IgG, immunoglobulin G; IgM, immunoglobulin M; RDT, S. Typhi rapid diagnostic test.
See this image and copyright information in PMC

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