Performance of C. Diff Quik Chek Complete and RIDASCREEN immunoassays and lack of Ct value concordance between Allplex GI– Bacteria(I) and Xpert Clostridioides difficile assays: a diagnostic accuracy study
- Author:
Kibum JEON
1
;
Nuri LEE
;
Hyun Soo KIM
;
Han-Sung KIM
;
Wonkeun SONG
;
Jae-Seok KIM
Author Information
- Publication Type:Original article
- From:Annals of Clinical Microbiology 2026;29(1):1-
- CountryRepublic of Korea
- Language:English
-
Abstract:
Background:Enzyme immunoassays (EIAs), which detect glutamate dehydrogenase (GDH) and toxin A/B, are widely used to screen for Clostridioides difficile infection (CDI); however, their sensitivity is lower than that of molecular assays. This study aimed to evaluate the performance of two EIAs, C. Diff Quik Chek Complete (QCC) and RIDASCREEN (RIDA), and investigate the cycle threshold (Ct) values from two real-time polymerase chain reaction (PCR) assays (Allplex GI–Bacteria(I) and Xpert C. difficile) in EIA-discordant samples.
Methods:A total of 180 clinical stool samples were tested using QCC, RIDA, and Allplex GI– Bacteria(I) PCR assays. The Xpert C. difficile assay was used to analyze discordant results.
Results:QCC and RIDA showed high sensitivities for GDH detection, 100.0% and 94.4%, respectively. QCC was significantly more sensitive than RIDA for toxin detection (51.4% vs. 28.6%, p = 0.007). In 25 EIA-discordant, Xpert positive samples, the Ct values of the toxin B gene ranged from 31.5 to 44.8 (mean, 38.1) for Allplex PCR and from 23.7 to 36.3 (mean, 30.4) for Xpert PCR. The Ct values of the two PCR assays were not significantly correlated (r = 0.201, p = 0.324).
Conclusion:QCC is a suitable initial immunological test for diagnosing CDI. The lack of correlation in the Ct values between the two real-time PCR assays suggests that assay-specific validation is necessary for cutoff level interpretation.
