Diagnosis of Clostridiodes difficile infection: Assessing the performance of Quik Chek complete kit assay versus the GeneXpert PCR assay at a major tertiary care center in Lebanon

Abstract

AimsTo evaluate the performance of the C. difficile Quik Chek Complete (QCC) (TechLab, USA) versus the GeneXpert C. difficile polymerase chain reaction (PCR) assay (Cepheid, CA, USA). MethodsA retrospective chart analysis conducted at the American University of Beirut Medical Center (AUBMC) covering the period from January 2015 to September 2018. ResultsA total of 788 samples were simultaneously tested by the two methods and analyzed in this study. 49% were positive with the QCC-EIA assay (GDH and/or toxins). The GeneXpert assay showed 40% positivity, based on the detection of either toxin B or binary toxin genes. Using GeneXpert as a reference test, the performance of C. difficile Quik Chek was evaluated in terms of sensitivity (96%), specificity (81%), PPV (77%) and NPV (97%). Among the concordant negative results with the QCC-EIA assay (GDH−/Toxins-), 97% were negative by GeneXpert, while among the concordant positive results (GDH+/Toxins+), 92% were positive by GeneXpert. Regarding the discordant QCC-EIA results (GDH+/Toxins-), 77% were positive by PCR. ConclusionC. difficile Quik Chek immunoassay is a solid method to use as an upfront for stool testing of C. difficile infections with satisfactory sensitivity and specificity when compared to GeneXpert assay. When results of the immunoassay are concordant for both the toxins and GDH components, it is very unlikely for the results to be different with molecular assays such as the GeneXpert. However, for discordant results, we recommend following up such cases with a molecular assay like GeneXpert.