A comparison study of three rapid immunoassays for the diagnosis of Clostridioides difficile infection

Current guidelines recommend the use of a two-step algorithm for the laboratory diagnosis of Clostridioides difficile infection (CDI). Several commercial rapid immunoassays that detect both GDH and toxin A/B in stool samples are available and could be used for both steps of the diagnostic algorithm. Our aim was to evaluate the performance of three of these rapid immunoassays and study pathogen characteristics that might affect the sensitivity of toxin A/B detection. Leftover material from routinely collected stool samples from patients suspected of CDI was analyzed with the three immunoassays, NAAT and culture. Whole genome sequencing was then used to evaluate C. difficile isolates recovered from the samples. The positive percent agreement between GDH detection and detection of tcdA by NAAT was 100% with all three immunoassays. The positive percent agreement for detection of toxin A/B, however, was considerably lower (50.0%, 51.7% and 71.4%) and freezing stool samples seemed to negatively affect the detection of both GDH and toxins. The isolates included in the study belonged to 23 different sequence types (ST) and all carried the tcdA and tcdB genes. The C. diff Quik Chek complete performed the best of the three immunoassays and when used in combination with NAAT is a viable option for the laboratory diagnosis of CDI.