Clostridioides difficile in outpatients: application of a diagnostic algorithm recommended by the European Society of Clinical Microbiology and Infectious Diseases

Abstract

This study aimed at evaluating in outpatients an algorithm for the laboratory diagnosis of Clostridioides (Clostridium) difficile infection (CDI), i.e., enzyme immunoassays (EIAs) detecting bacterial glutamate dehydrogenase (GDH) and toxin A/B, followed by polymerase chain reaction (PCR) analyses of samples with discordant EIA results.In total, 9802 examinations of stool samples by GDH and toxin EIAs performed in 7263 outpatients and 488 inpatients were analyzed retrospectively. Samples with discordant EIA results had been tested by a commercially available PCR assay detecting genes of the C. difficile-specific triose phosphate isomerase (tpi) and toxin B (tcdB). Concordant EIA results (686 C. difficile-positive, 8121 negative) were observed for 8807 (89.8%; 95% CI, 89.2–90.4%) samples. Of 958 samples with discordant EIA results, 895 were analyzed using PCR and 580 of 854 GDH-positive/borderline, toxin-negative samples (67.9%; 95% CI, 64.7–71.0%) were positive for tpi and tcdB, while 274 samples (32.1%; 95% CI, 29.0–35.3%) were tcdB-negative. In contrast, 35 of 41 GDH-negative, toxin-positive/borderline samples (85.4%; 95% CI, 71.2–93.5%) were tcdB-negative. Still, 6 samples (14.6%; 95% CI, 6.5–28.8%) yielded positive PCR results for both genes.In conclusion, around 90% of the samples were analyzed appropriately by only applying EIAs. Approximately one third of the PCR-analyzed samples were tcdB-negative; thus, patients most likely did not require CDI treatment.

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“…Of the 9,802 stool samples studied, approximately 90% concordance was noted between GDH and EIA testing (95% confidence interval [CI] 89.2–90.4%). However, of the discordant GDH+/EIA– samples, 68% were positive by NAAT (95% CI 64.7–71.0%), and of the discordant GDH–/EIA+ samples, 85% were negative by NAAT (95% CI 71.2–93.5%) 40 . It is generally accepted that in facilities that use screening practices (e.g.…”

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“…A newer testing regimen involving a 2-step strategy is emerging where the first step is to use glutamate dehydrogenase (GDH) as a screening strategy [19]. As a screening assay, GDH is sensitive but not specific for a diagnosis of CDI [22]. A negative GDH would effectively rule out CDI.…”