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

Abstract

Blood and bone marrow cultures are considered the gold standard for the diagnosis of typhoid, but those methods require infrastructure and skilled manpower 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 reference standard in a multicenter study. This was a prospective and retrospective multicenter diagnostic accuracy study conducted in two geographically distant typhoid-endemic areas (Pakistan and Kenya; NCT04801602). 9 RDTs were evaluated were including 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. 531 serum samples were evaluated (264 blood-culture positive; 267 blood-culture negative). The sensitivity of RDTs varied widely (range 0–78.8%), 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 and 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 endemic regions. These findings highlight the clear need for new, more accurate SalmonellaTyphi tests. Clinical Trial Registration ID #: NCT04801602