Dataset Information

Clostridium difficile PCR Cycle Threshold Predicts Free Toxin.

ABSTRACT: There is no stand-alone Clostridium difficile diagnostic that can sensitively and rapidly detect fecal free toxins. We investigated the performance of the C. difficile PCR cycle threshold (CT ) for predicting free toxin status. Consecutive stool samples (n = 312) positive for toxigenic C. difficile by the GeneXpert C. difficile/Epi tcdB PCR assay were tested with the rapid membrane C. Diff Quik Chek Complete immunoassay (RMEIA). RMEIA toxin-negative samples were tested with the cell cytotoxicity neutralization assay (CCNA) and tgcBIOMICS enzyme-linked immunosorbent assay (ELISA). Using RMEIA alone or in combination with CCNA and/or ELISA as the reference method, the accuracy of CT was measured at different CT cutoffs. Using RMEIA as the reference method, a CT cutoff of 26.35 detected toxin-positive samples with a sensitivity, specificity, positive predictive value, and negative predictive value of 96.0% (95% confidence interval [CI], 90.2% to 98.9%), 65.9% (95% CI, 59.0% to 72.2%), 57.4% (95% CI, 52.7% to 62%), and 97.1% (95% CI, 92.8% to 98.9), respectively. Inclusion of CCNA in the reference method improved CT specificity to 78.0% (95% CI, 70.7% to 84.2%). Intercartridge lot CT variability measured as the average coefficient of variation was 2.8% (95% CI, 1.2% to 3.2%). Standardizing the input stool volume did not improve CT toxin specificity. The median CT values were not significantly different between stool samples with Bristol scores of 5, 6, and 7, between pediatric and adult samples, or between presumptive 027 and non-027 strains. In addition to sensitively detecting toxigenic C. difficile in stool, on-demand PCR may also be used to accurately predict toxin-negative stool samples, thus providing additional results in PCR-positive stool samples to guide therapy.

SUBMITTER: Senchyna F

PROVIDER: S-EPMC5648702 | biostudies-literature | 2017 Sep

REPOSITORIES: biostudies-literature

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Clostridium difficile PCR Cycle Threshold Predicts Free Toxin.

Senchyna Fiona F Gaur Rajiv L RL Gombar Saurabh S Truong Cynthia Y CY Schroeder Lee F LF Banaei Niaz N

Journal of clinical microbiology 20170614 9

There is no stand-alone Clostridium difficile diagnostic that can sensitively and rapidly detect fecal free toxins. We investigated the performance of the C. difficile PCR cycle threshold (CT ) for predicting free toxin status. Consecutive stool samples (n = 312) positive for toxigenic C. difficile by the GeneXpert C. difficile/Epi tcdB PCR assay were tested with the rapid membrane C. Diff Quik Chek Complete immunoassay (RMEIA). RMEIA t ...[more]

PMID: 28615471

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Project description:The objective of the present study was to evaluate the value of the PCR cycle threshold (CT ) for predicting the recurrence/severity of infection compared to that of toxin detection plus clinical variables. First episodes of Clostridium difficile infection (CDI) diagnosed during 2015 at our institution were included. Samples were tested for glutamate dehydrogenase (GDH) and toxin A/B by use of a single enzyme immunoassay (EIA). The Xpert C. difficile PCR assay was performed on GDH-positive samples. Medical data were reviewed by investigators blinded to diagnostic results for comparison of patients with and without recurrence or a poor outcome (severe/severe-complicated CDI episodes and all-cause death). We generated two sets of predictive models by incorporating the presence of a positive toxin EIA ("EIA-including model") or the optimal PCR CT cutoff value ("PCR-including model") into the clinical variables. Among 227 episodes of CDI included in the study, the rates of recurrence and poor outcome were 15.8% and 30.8%, respectively. The mean PCR CT was lower for episodes with recurrence (24.00?±?3.28 versus 26.02?±?4.54; P?=?0.002) or a poor outcome (24.9?±?4.24 versus 26.05?±?4.47; P = 0.07). The optimal cutoff value for recurrence was 25.65 (sensitivity, 77.8% [95% confidence interval {CI}, 60.9 to 89.9]; and specificity, 46.6% [95% CI, 39.4 to 53.9]). The area under the receiver operator characteristics curve (auROC) for the "PCR-including model" was similar to that for the "EIA-including model" (0.785 versus 0.775, respectively). The optimal PCR CT value for poor outcome was 27.55 (sensitivity, 78.6% [95% CI, 67.1 to 87.5]; and specificity, 35.7% [95% CI, 28.2 to 43.7]). The auROC of the "PCR-including model" was again similar to that of the "EIA-including model" (0.804 versus 0.801). Despite the inverse correlation between PCR CT and the risk of CDI recurrence/severity, this determination does not meaningfully increase the predictive value of clinical variables plus toxin EIA.

Dataset Information

Clostridium difficile PCR Cycle Threshold Predicts Free Toxin.

Publications

Clostridium difficile PCR Cycle Threshold Predicts Free Toxin.

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