Rapid tests as a practical alternative to slide agglutination for the confirmation of V. cholerae O1

ObjectivesSlide agglutination is a crucial step for confirming cholera culture by determining serogroup/serotype. Rapid diagnostic tests (RDTs), typically used on stool, may provide a practical alternative, as they are easy to use, store and require minimal training. This study evaluates the concordance of V. cholerae O1/O139 detection from presumptive colonies by slide agglutination with RDTs. MethodsPatients ([≥]1 year) with acute watery diarrhea at the icddr,b Dhaka hospital were enrolled. Stool samples cultured on Thiosulfate-Citrate-Bile Salts-Sucrose media, and presumptive colonies were sub-cultured on Gelatin Agar. Isolates were then tested by slide agglutination and four commercial cholera RDTs. ResultsFrom 4-February-2024 through 31-January-2025, 1,331 patients with acute watery diarrhea were enrolled, 952 had presumptive colonies and 408 (31%) were culture-confirmed as V. cholerae O1. We tested 952, 505, 505, and 467 presumptive colonies with Cholkit, SD-Bioline, Crystal VC O1/O139, and Crystal VC O1 RDT kits, respectively. RDTs showed near-perfect concordance with slide agglutination. Using slide agglutination as the reference, the sensitivity of the RDT kits ranged from 99.5-100% and the specificity from 99-99.8%. No V. cholerae O139 was detected by slide agglutination or PCR. ConclusionsRDTs offer a practical, and potentially easier alternative to slide agglutination of presumptive cholerae colonies within typical cholera culture protocols. This may help to provide a pathway to quick confirmation of outbreaks in settings where lab facilities and reagents may be limited.