Clostridioides difficile infection (CDI) continues to cause significant morbidity and avoidable mortality worldwide. Results from an ultra-sensitive toxin immunoassay (Singlulex Clarity C. diff toxins A/B assay) were compared with those of various other diagnostic and reference methods/algorithms for the detection of .


293 residual clinical stool samples were tested using the Singulex assay. In total, 188 samples were tested by GDH and 239 were tested by PCR. All toxin B PCR (Serosep EntericBio assay) positive samples (n=168) and prospectively tested GDH samples (n=97) were also tested using membrane-type toxin EIA (MT-EIA; Techlab Tox A/B Quik Chekò). Culture (alcohol shock and Brazier’s media; Oxoid) and ribotyping (capillary electrophoresis using Bidet primers) information was available for 205 samples.


The positive percent agreement (PPA) and negative percent agreement (NPA) of the Singulex Clarity C. diff toxins A/B assay compared with: GDH; toxin EIA; PCR; GDH/toxin EIA; GDH/toxin EIA/PCR; PCR/toxin EIA and culture were – 61% & 92%; 97% & 50%; 69% & 90%; 100% & 51%; 81% & 77%; 96% & 65%; and 69% AND 52% respectively.


The Singulex Clarity C. diff toxins A/B assay had high PPA compared to toxin EIA and multistep algorithms ending with toxin EIA, and high NPA compared to PCR and a multistep algorithm ending with PCR. The Singulex Clarity assay has the potential to be used as a standalone test for CDI diagnosis; additional clinical studies are required and will soon be underway.

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