Diagnosis and outcome of Clostridium difficile infection by toxin enzyme immunoassay and polymerase chain reaction in an island population

Comparative evaluation of the STANDARD M10 and Xpert C. difficile assays for detection of toxigenic Clostridioides difficile in stool specimens

This study compared the performance of two commercial molecular assays, the STANDARD M10 Clostridioides difficile assay (M10) and the Xpert C. difficile assay (Xpert), for detecting toxigenic C. difficile in stool specimens. A total of 487 consecutive stool specimens submitted for routine C. difficile testing between June and November 2023 were included. Following routine testing using C. DIFF QUIK CHEK COMPLETE (QCC), M10 and Xpert were tested in parallel, alongside toxigenic culture (reference standard). Additionally, two-step algorithms, using QCC on the first step and either M10 or Xpert on the second step, were assessed. Both M10 and Xpert demonstrated a sensitivity and negative predictive value (NPV) of 100%. M10 exhibited significantly higher specificity and positive predictive value (PPV; 91.9% and 64.2%, respectively) than Xpert (90.3% and 59.8%, respectively). Both two-step algorithms showed a sensitivity and NPV of 98.4% and 99.8%, respectively. The specificity and PPV of the two-step algorithm using M10 (95.2% and 75.0%, respectively) were slightly higher than those of the one using Xpert (94.8% and 73.2%, respectively), without statistical significance. Receiver operating characteristic curve analysis, assessing the predictive ability of cycle threshold (Ct) values for the detection of free toxin, exhibited an area under the curve of 0.825 for M10 and 0.843 for Xpert. This indicates the utility of Ct values as predictors for the detection of free toxin in both assays. In conclusion, M10 proves to be an effective diagnostic tool with performance comparable to Xpert, whether utilized independently or as part of a two-step algorithm.

Clinical outcomes and treatment necessity in patients with toxin-negative Clostridioides difficile stool samples

PURPOSE

The clinical significance of negative toxin enzyme immunoassays (EIA) for Clostridioides difficile infections (CDIs) is unclear. Our study aimed to investigate the significance of toxin EIA-negative in the diagnosis and prognosis of CDI.

METHODS

All stool specimens submitted for C. difficile toxin EIA testing were cultured to isolate C. difficile. In-house PCR for tcdA, tcdB, cdtA, and cdtB genes were performed using C. difficile isolates. Stool specimens were tested with C. difficile toxins A and B using EIA kit (RIDASCREEN Clostridium difficile toxin A/B, R-Biopharm AG, Darmstadt, Germany). Characteristics and subsequent CDI episodes of toxin EIA-negative and -positive patients were compared.

RESULTS

Among 190 C. difficile PCR-positive patients, 83 (43.7%) were toxin EIA-negative. Multivariate analysis revealed independent associations toxin EIA-negative results and shorter hospital stays (OR = 0.98, 95% CI 0.96-0.99, p = 0.013) and less high-risk antibiotic exposure in the preceding month (OR = 0.38, 95% CI 0.16-0.94, p = 0.035). Toxin EIA-negative patients displayed a significantly lower white blood cell count rate (11.0 vs. 35.4%, p < 0.001). Among the 54 patients who were toxin EIA-negative and did not receive CDI treatment, three (5.6%) were diagnosed with CDI after 7-21 days without complication.

CONCLUSION

Our study demonstrates that toxin EIA-negative patients had milder laboratory findings and no complications, despite not receiving treatment. Prolonged hospitalisation and exposure to high-risk antibiotics could potentially serve as markers for the development of toxin EIA-positive CDI.

Clinical Outcomes and Management of NAAT-Positive/Toxin-Negative Clostridioides difficile Infection: A Systematic Review and Meta-Analysis

BACKGROUND

Standalone nucleic acid amplification tests (NAATs) are frequently used to diagnose Clostridioides difficile infections (CDI), although they may be unable to distinguish colonization from disease. A 2-stage algorithm pairing NAATs with toxin immunoassays (Toxin) may improve specificity. We evaluated clinical outcomes of patients who were NAAT+/Toxin+ versus NAAT+/Toxin- and treated versus untreated NAAT+/Toxin- cases through systematic review and meta-analysis.

METHODS

We searched EMBASE and MEDLINE from inception to April 1, 2023 for articles comparing CDI outcomes among symptomatic patients tested by NAAT and Toxin tests. The risk differences (RD) of all-cause mortality and CDI recurrence were computed by random effects meta-analysis between patients who were NAAT+/Toxin+ and NAAT+/Toxin-, as well as between patients who were NAAT+/Toxin- and treated or untreated.

RESULTS

Twenty-six observational studies comprising 12 737 patients were included. The 30-day all-cause mortality was not significantly different between those who were NAAT+/Toxin+ (8.4%) and NAAT+/Toxin- (6.7%) (RD = 0.41%, 95% confidence interval [CI] = -.67, 1.49). Recurrence at 60 days was significantly higher among patients who were NAAT+/Toxin+ (19.8%) versus NAAT+/Toxin- (11.0%) (RD = 7.65%, 95% CI = 4.60, 10.71). Among treated compared to untreated NAAT+/Toxin- cases, the all-cause 30-day mortalities were 5.0% and 12.7%, respectively (RD = -7.45%, 95% CI = -12.29, -2.60), but 60-day recurrence was not significantly different (11.6% vs 7.0%, respectively; RD = 5.25%, 95% CI -1.71, 12.22).

CONCLUSIONS

Treatment of patients who were NAAT+/Toxin- was associated with reduced all-cause mortality but not recurrence. Although subject to the inherent limitations of observational studies, these results suggest that some patients who are NAAT+/Toxin- may benefit from treatment.

Clostridioides difficile Infection: The Challenge, Tests, and Guidelines

Clostridioides difficile is a dangerous human pathogen because it can grow to high numbers in the intestine, cause colitis with its potent toxins, and persist as spores. C. difficile infection (CDI) is the primary hospital-acquired infection in North America and Europe, and it now is a global disease. Even with newer laboratory tests, there still is confusion on accurately diagnosing this disease. Three guidelines from three different healthcare-affiliated societies have recently been published. Consensus consolidated recommendations from these guidelines should be recognized by healthcare professionals, who need to understand why this disease continues to be difficult to diagnose and need a clear understanding of the advantages and limitations of current tests. Hopefully, these combined efforts will lead to an improvement in the recognition of this pathogen and a reduction in the suffering and economic loss caused by CDI.

Clinical significance of a positive Clostridioides difficile glutamate dehydrogenase test on the outcomes of hospitalized older patients

AIM

Clostridioides difficile infection worsens the outcome of older hospitalized patients; thus, its diagnosis is necessary for the nosocomial infection control. The standard diagnostic test's limited sensitivity for Clostridioides difficile infection, an enzyme immunoassay for Clostridioides difficile toxins, is of clinical concern. Glutamate dehydrogenase detection is usually tested combined with Clostridioides difficile toxins. However, the clinical significance of a positive glutamate dehydrogenase result is unclear. We evaluated the association between positive glutamate dehydrogenase results, in-hospital mortality and hospital stay length among older patients with suspected Clostridioides difficile infection.

METHODS

In this retrospective cohort study, we examined the data of patients who received antibiotics (except for Clostridioides difficile infection treatment) after admission and tested for Clostridioides difficile infection using an enzyme immunoassay for Clostridioides difficile toxins and glutamate dehydrogenase in a secondary care hospital located in a rural region with high aging rate, between 2015 and 2018.

RESULTS

In total, 188 patients were included (83.5% of them aged >75 years). Glutamate dehydrogenase positivity was independently associated with in-hospital mortality (adjusted odds ratio 2.19, 95% confidence interval 1.14-4.21) and hospital stay length (regression coefficient 16.0, 95% confidence interval 5.15-26.9). Clostridioides difficile toxin positivity was independently associated with hospital stay duration (regression coefficient 14.5, 95% confidence interval 0.04-29.1), unlike in-hospital mortality.

CONCLUSIONS

Glutamate dehydrogenase was closely related to in-hospital mortality and prolonged hospitalization compared with Clostridioides difficile toxin. Clinicians should not neglect glutamate dehydrogenase-positive patients, even when they are Clostridioides difficile toxin-negative, and consider them as having poor prognostic potential. Geriatr Gerontol Int 2020; 20: 1138-1144.

Toxin Enzyme Immunoassays Detect Clostridioides difficile Infection With Greater Severity and Higher Recurrence Rates

BACKGROUND

Few data suggest that Clostridioides difficile infections (CDIs) detected by toxin enzyme immunoassay (EIA) are more severe and have worse outcomes than those detected by nucleic acid amplification tests (NAATs) only. We compared toxin- positive and NAAT-positive-only CDI across geographically diverse sites.

METHODS

A case was defined as a positive C. difficile test in a person ≥1 year old with no positive tests in the prior 8 weeks. Cases were detected during 2014-2015 by a testing algorithm (specimens initially tested by glutamate dehydrogenase and toxin EIA; if discordant results, specimens were reflexed to NAAT) and classified as toxin positive or NAAT positive only. Medical charts were reviewed. Multivariable logistic regression models were used to compare CDI-related complications, recurrence, and 30-day mortality between the 2 groups.

RESULTS

Of 4878 cases, 2160 (44.3%) were toxin positive and 2718 (55.7%) were NAAT positive only. More toxin-positive than NAAT-positive-only cases were aged ≥65 years (48.2% vs 38.0%; P < .0001), had ≥3 unformed stools for ≥1 day (43.9% vs 36.6%; P < .0001), and had white blood cell counts ≥15 000 cells/µL (31.4% vs 21.4%; P < .0001). In multivariable analysis, toxin positivity was associated with recurrence (adjusted odds ratio [aOR], 1.89; 95% confidence interval [CI], 1.61-2.23), but not with CDI-related complications (aOR, 0.91; 95% CI, .67-1.23) or 30-day mortality (aOR, 0.95; 95% CI, .73-1.24).

CONCLUSIONS

Toxin-positive CDI is more severe, but there were no differences in adjusted CDI-related complication and mortality rates between toxin-positive and NAAT-positive-only CDI that were detected by an algorithm that utilized an initial glutamate dehydrogenase screening test.

Changes in the Association between Diagnostic Testing Method, PCR Ribotype, and Clinical Outcomes from Clostridioides difficile Infection: One Institution's Experience

BACKGROUND

In patients with Clostridioides difficile infection (CDI), the relationship between clinical, microbial, and temporal/epidemiological trends relate and disease severity and adverse outcomes is incompletely understood. Here, in a follow-up to our study conducted in 2010-2013, we evaluate stool toxin levels and C. difficile PCR ribotypes. We hypothesized that elevated stool toxins and infection with ribotype 027 associate with severe disease and adverse outcomes.

METHODS

In a cohort of 565 subjects at the University of Michigan with CDI diagnosed by positive testing for toxins A/B by EIA or PCR for the tcdB gene, we quantified stool toxin levels via a modified cell cytotoxicity assay, isolated C. difficile by anaerobic culture, and performed PCR ribotyping. Severe CDI was defined by IDSA criteria, and primary outcomes were all-cause 30-day mortality and a composite of colectomy, ICU admission, and/or death attributable to CDI within 30 days. Analyses included bivariable tests and adjusted logistic regression.

RESULTS

199 samples were diagnosed by EIA and 447 were diagnosed by PCR. Toxin positivity associated with IDSA severity, but not primary outcomes. In 2016, compared to 2010-2013, ribotype 106 newly emerged, accounting for 10.6% of strains, ribotype 027 fell from 16.5% to 9.3%, and ribotype 014-027 remained stable at 18.9%. Ribotype 014-020 associated with IDSA severity and 30-day mortality (P=.001).

CONCLUSION

Toxin positivity by EIA and CCA associated with IDSA severity, but not with subsequent adverse outcomes. The molecular epidemiology of C. difficile has shifted, and this may have implications for the optimal diagnostic strategy for and clinical severity of CDI.

The Role of Diagnostic Stewardship in Clostridioides difficile Testing: Challenges and Opportunities

PURPOSE OF REVIEW

Accurate and timely diagnosis of Clostridioides difficile infection (CDI) is imperative to prevent C. difficile transmission and reduce morbidity and mortality due to CDI, but CDI laboratory diagnostics are complex. The purpose of this article is to review the role of laboratory tests in the diagnosis of CDI, and the role of diagnostic stewardship in optimization of C. difficile testing.

RECENT FINDINGS

Results from C. difficile diagnostic tests should be interpreted with an understanding of the strengths and limitations inherent in each testing approach. Use of highly sensitive molecular diagnostic tests without accounting for clinical signs and symptoms may lead to over-diagnosis of CDI and increased facility CDI rates. Current guidelines recommend a two-step, algorithmic approach for testing. Diagnostic stewardship interventions, such as education, order sets, order search menus, reflex orders, hard and soft stop alerts, electronic references, feedback and benchmarking, decision algorithms, and predictive analytics may help improve use of C. difficile laboratory tests and CDI diagnosis. The diagnostic stewardship approaches with the highest reported success rates include computerized clinical decision support (CCDS) interventions, face-to-face feedback, and real-time evaluations.

SUMMARY

CDI is a clinical diagnosis supported by laboratory findings. Together, clinical evaluation combined with diagnostic stewardship can optimize the accurate diagnosis of CDI.

South African Society of Clinical Microbiology Clostridioides difficile infection diagnosis, management and infection prevention and control guideline

Clostridioides difficile infection (CDI) is a problem in both developed and developing countries and is a common hospital-acquired infection. This guideline provides evidence-based practical recommendations for South Africa and other developing countries. The scope of the guideline includes CDI diagnostic approaches; adult, paediatric and special populations treatment options; and surveillance and infection prevention and control recommendations.

The Epidemiology of Community Clostridium difficile Infection: A Five-Year Population-Based Study on the Bailiwick of Jersey, Channel Islands

We studied healthcare-associated and community-associated Clostridium difficile infection (CDI) in Jersey, Channel Islands (2008–2012). The Island’s stable population has reliable denominator data, a clearly defined at-risk population, and healthcare contact that is easily followed. The vast majority of CDI cases had had recent healthcare contact, and true community-associated disease is extremely rare.

Infect Control Hosp Epidemiol 2018;39:603–607

Nucleic Acid Amplification Test Quantitation as Predictor of Toxin Presence in Clostridium difficile Infection

Multistep algorithmic testing in which a sensitive nucleic acid amplification test (NAAT) is followed by a specific toxin A and toxin B enzyme immunoassay (EIA) is among the most accurate methods for Clostridium difficile infection (CDI) diagnosis. The obvious shortcoming of this approach is that multiple tests must be performed to establish a CDI diagnosis, which may delay treatment. Therefore, we sought to determine whether a preliminary diagnosis could be made on the basis of the quantitative results of the first test in algorithmic testing, which provide a measure of organism burden. To do so, we retrospectively analyzed two large collections of samples (n = 2,669 and n = 1,718) that were submitted to the laboratories of two Dutch hospitals for CDI testing. Both hospitals apply a two-step testing algorithm in which a NAAT is followed by a toxin A/B EIA. Of all samples, 208 and 113 samples, respectively, tested positive by NAAT. Among these NAAT-positive samples, significantly lower mean quantification cycle (C_q ) values were found for patients whose stool eventually tested positive for toxin, compared with patients who tested negative for toxin (mean C_q values of 24.4 versus 30.4 and 26.8 versus 32.2; P < 0.001 for both cohorts). Receiver operating characteristic curve analysis was performed to investigate the ability of C_q values to predict toxin status and yielded areas under the curve of 0.826 and 0.854. Using the optimal C_q cutoff values, prediction of the eventual toxin A/B EIA results was accurate for 78.9% and 80.5% of samples, respectively. In conclusion, C_q values can serve as predictors of toxin status but, due to the suboptimal correlation between the two tests, additional toxin testing is still needed.

Point-Counterpoint: What Is the Optimal Approach for Detection of Clostridium difficile Infection?

INTRODUCTIONIn 2010, we published an initial Point-Counterpoint on the laboratory diagnosis of Clostridium difficile infection (CDI). At that time, nucleic acid amplification tests (NAATs) were just becoming commercially available, and the idea of algorithmic approaches to CDI was being explored. Now, there are numerous NAATs in the marketplace, and based on recent proficiency test surveys, they have become the predominant method used for CDI diagnosis in the United States. At the same time, there is a body of literature that suggests that NAATs lack clinical specificity and thus inflate CDI rates. Hospital administrators are taking note of institutional CDI rates because they are publicly reported. They have become an important metric impacting hospital safety ratings and value-based purchasing; hospitals may have millions of dollars of reimbursement at risk. In this Point-Counterpoint using a frequently asked question approach, Ferric Fang of the University of Washington, who has been a consistent advocate for a NAAT-only approach for CDI diagnosis, will discuss the value of a NAAT-only approach, while Christopher Polage of the University of California Davis and Mark Wilcox of Leeds University, Leeds, United Kingdom, each of whom has recently written important articles on the value of toxin detection in the diagnosis, will discuss the impact of toxin detection in CDI diagnosis.