Diagnostic utilities of a fully automated molecular test for toxigenic Clostridium difficile

Budget Impact Analysis of Adopting a One-Step Nucleic Acid Amplification Testing (NAAT) Alone Diagnostic Pathway for Clostridioides difficile in Japan Compared to a Two-Step Algorithm with Glutamate Dehydrogenase/Toxin Followed by NAAT

Clostridioides difficile infection (CDI) is a major healthcare-associated infection that leads to a significant health economic burden in Japan. Using a decision tree model, we evaluated the budget impact of adopting a one-step nucleic acid amplification test (NAAT) alone pathway compared to a two-step diagnostic algorithm with glutamate dehydrogenase (GDH) and toxin antigen, followed by NAAT. The analysis was conducted from the government payer's perspective for 100,000 symptomatic, hospitalized adults requiring a CDI diagnostic test. One-way sensitivity analysis was conducted for all data inputs. The NAAT alone strategy costed JPY 225,886,360 (USD 2,424,714) more, but was more effective, resulting in 1749 more patients accurately diagnosed and 91 fewer deaths compared to the two-step algorithm. Additionally, the NAAT alone pathway costed JPY 26,146 (USD 281) less per true positive CDI diagnosed. The total budget impact, and cost per CDI diagnosed was most sensitive to GDH sensitivity in one-way sensitivity analysis, where a lower GDH sensitivity resulted in greater cost savings with the NAAT alone pathway. Findings from this budget impact analysis can guide the adoption of a NAAT alone pathway for CDI diagnosis in Japan.

Accuracy of diagnostic assays for the detection of Clostridioides difficile: A systematic review and meta-analysis

INTRODUCTION

Clostridioides difficile Infection (CDI) has been identified as one of the main causes of nosocomial infection all across the world. Rapid diagnosis of CDI is difficult and poses a significant challenge to physicians worldwide. We undertook a systematic review and meta-analysis to evaluate rapid tests' diagnostic accuracy against toxigenic culture as the reference standard for CDI.

METHOD

We searched the PubMed/MEDLINE and EMBASE databases for the relevant records. The QUADAS-2 tool was used to assess the quality of the studies. Diagnostic accuracy measures [i.e., sensitivity, specificity, diagnostic odds ratio (DOR), positive likelihood ratios (PLR), negative likelihood ratios (NLR), and the area under the curve (AUC)] were pooled with a random-effects model. All statistical analyses were performed with Meta-DiSc (Version 1.4, Cochrane Colloquium, Barcelona, Spain) and RevMan (version 5.3; The Nordic Cochrane Centre, the Cochrane Collaboration, Copenhagen, Denmark).

RESULTS

We reviewed retrieved records and identified 63 studies that met the inclusion criteria. 26 were about enzyme immunoassay (EIA) (our main index test). The sensitivity of GDH and Tox A/B EIAs were 82% (95% CI: 79-84) and 75% (95% CI: 70-79), respectively. On the other hand, the specificity of GDH EIA was 91% (95% CI: 90-92) and the specificity of Tox A/B EIA was 95% (95% CI: 94-96). Among other index tests, BD Max with 92% has the most sensitivity and cell cytotoxicity neutralization assay (CCNA) has the most specificity (100%).

CONCLUSION

This meta-analysis demonstrated that EIAs could be reliable methods for detecting CDI based on their sensitivity, specificity, time and cost-effectiveness, and simplicity in the procedure. Further work to improve rapid tests would benefit from improvements to the methodology.

Laboratory Diagnostic Methods for Clostridioides difficile Infection: the First Systematic Review and Meta-analysis in Korea

Background

Various methods are used for the diagnosis of Clostridioides difficile infection (CDI). We systematically analyzed and investigated the performance of current laboratory diagnostic methods for CDI.

Methods

We performed systematic review and meta-analysis of studies in PubMed, Web of Science, Cochrane Library, and KoreaMed. The following methods were evaluated glutamate dehydrogenase (GDH) enzyme immunoassays (GDH EIAs), toxin A and B detection by enzyme immunoassays (toxin AB EIAs), and nucleic acid amplification tests (NAATs) for C. difficile toxin genes. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of each method were calculated.

Results

Based on 39 studies, the pooled sensitivities/specificities were 92.7%/94.6%, 57.9%/97.0%, and 90.0%/95.8% for GDH EIAs, toxin AB EIAs, and NAATs, respectively, compared with those of toxigenic culture. The pooled sensitivities of automated EIAs were significantly higher than those of non-automated EIAs for both GDH and toxins A and B. The pooled sensitivity of Xpert C. difficile was significantly higher than those of other NAATs. PPVs increased as CDI prevalence increased, and NPVs were excellent when CDI prevalence was low; at CDI prevalence of 5%, PPV = 37%-65% and NPV = 97%-100%; at CDI prevalence of 50%, PPV = 92%-97% and NPV = 65%-98%.

Conclusions

Toxin AB EIAs still show unsatisfactory sensitivity, whereas GDH EIAs and NAATs show relatively high sensitivity. However, toxin AB EIAs are the most specific tests. This study may provide useful information for CDI diagnosis.

Usefulness of a newly developed high-speed polymerase chain reaction analysis system for the diagnosis of Clostridioides difficile infection

INTRODUCTION

The incidence of Clostridioides difficile infection (CDI) has been continuously increasing and thereby became an important issue worldwide. Appropriate diagnosis, management, and infection control are required for patients with CDI. Enzyme immunoassay (EIA) is a widely used standard diagnostic tool for C. difficile-specific glutamate dehydrogenase (GDH) and C. difficile toxins (toxins A and B). However, the sensitivity of EIA in detecting C. difficile toxins has been reported to be relatively low, resulting in CDI underdiagnosis. Therefore, nucleic acid amplification tests (NAAT) are recently developed for higher sensitivity/specificity test.

METHODS

In this study, a total of 279 stool samples submitted for CDI diagnosis were examined using an independently developed new high-speed polymerase chain reaction (PCR) device (PathOC RightGene, Metaboscreen). In parallel, results were compared with those of definitive diagnosis and conventional diagnostic methods (EIA, real-time PCR) to assess the inspection accuracy.

RESULTS

PathOC RightGene showed high sensitivity (96.7%) and specificity (96.7%). Regarding the measurement time, C. difficile-specific and C. difficile toxin genes were simultaneously detected in approximately 25 min for one sample (including the preprocessing and measurement time).

CONCLUSION

PathOC RightGene has been found to show both excellent sensitivity and rapidity and thus can be used for the reliable and early diagnosis, which are needed for the appropriate management of CDI.

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.

The reference method influence on the sensitivity of the Clostridium difficile enzyme immunoassays: A meta analysis

The use of enzyme immunoassays to screen for toxins A and B produced by Clostridium difficile is a common procedure in algorithms designed for its detection. Moreover, the absence of a unique test capable of providing reliable results at low cost motivates a great discussion about which algorithm is the best. Thus, several studies have evaluated the performance of these enzyme immunoassays. However, all fail to provide sufficient explanations for the different behaviours observed in different studies that evaluate the same index test against a common reference method. Our main goal was to find out which factors affect the sensitivity of these assays, since the specificity is very close to 1. In this research, we verified that sensitivity increases with the prevalence rate and with the proportion of reported cases of onset diarrhea. Therefore, its use is advisable for high prevalence rates (e.g. in an epidemic setting). As far as reference methods are concerned, nucleic acid amplification tests can be used as a reference method, with a performance similar to the well-accepted toxigenic culture. The method chosen for toxigenicity screening in a toxigenic culture also seems to affect the evaluation performance of tests and should be better studied in the future.

Machine learning analysis to identify the association between risk factors and onset of nosocomial diarrhea: a retrospective cohort study

BACKGROUND

Although several risk factors for nosocomial diarrhea have been identified, the detail of association between these factors and onset of nosocomial diarrhea, such as degree of importance or temporal pattern of influence, remains unclear. We aimed to determine the association between risk factors and onset of nosocomial diarrhea using machine learning algorithms.

METHODS

We retrospectively collected data of patients with acute cerebral infarction. Seven variables, including age, sex, modified Rankin Scale (mRS) score, and number of days of antibiotics, tube feeding, proton pump inhibitors, and histamine 2-receptor antagonist use, were used in the analysis. We split the data into a training dataset and independant test dataset. Based on the training dataset, we developed a random forest, support vector machine (SVM), and radial basis function (RBF) network model. By calculating an area under the curve (AUC) of the receiver operating characteristic curve using 5-fold cross-validation, we performed feature selection and hyperparameter optimization in each model. According to their final performances, we selected the optimal model and also validated it in the independent test dataset. Based on the selected model, we visualized the variable importance and the association between each variable and the outcome using partial dependence plots.

RESULTS

Two-hundred and eighteen patients were included. In the cross-validation within the training dataset, the random forest model achieved an AUC of 0.944, which was higher than in the SVM and RBF network models. The random forest model also achieved an AUC of 0.832 in the independent test dataset. Tube feeding use days, mRS score, antibiotic use days, age and sex were strongly associated with the onset of nosocomial diarrhea, in this order. Tube feeding use had an inverse U-shaped association with the outcome. The mRS score and age had a convex downward and increasing association, while antibiotic use had a convex upward association with the outcome.

CONCLUSION

We revealed the degree of importance and temporal pattern of the influence of several risk factors for nosocomial diarrhea, which could help clinicians manage nosocomial diarrhea.

Evaluation of a nucleic acid amplification assay for the diagnosis of Clostridioides difficile infection

Clostridioides difficile is the leading cause of healthcare-associated diarrhea and the laboratory diagnosis of Clostridioides difficile infection (CDI) continues to be challenging. Accurate and rapid identification of C. difficile will reduce unnecessary antibiotic use and ensure contact isolation to control the spread of CDI. In this study, diagnostic performance of BD MAX Cdiff assay (Becton Dickinson, USA) was evaluated for the detection of C. difficile in 2502 fresh stool samples from hospitalized children and adult patients and the results were compared to toxigenic culture. The frequency of CDI in adults and pediatric patients were found as 3.3% and 6.2%, respectively. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of BD MAX Cdiff assay were found as; 100%, 99.7%, 93%, and 100% for all patients; 100%, 99.7%, 96.2%, and 100% for pediatric patients; and 100%, 99.6%, 90.2%, and 100% for adult patients, respectively. We concluded that BD MAX Cdiff assay with high sensitivity, specificity, and PPV is useful for the diagnosis of CDI. With a high NPV of 100%, BD MAX Cdiff assay is also suitable for the exclusion of CDI.

Molecular epidemiology of Clostridioides difficile and risk factors for the detection of toxin gene-positive strains

In this study, we investigated all Clostridioides difficile strains isolated from stool samples in Nagasaki University Hospital between January 2012 and December 2014. Toxin genes (tcdA, tcdB and cdtA/cdtB) were analyzed for multiplex PCR in a total of 213 strains. In the toxin gene-positive strain, PCR ribotyping was conducted using capillary gel electrophoresis-based PCR and the Webribo database. Patients' backgrounds were analyzed by departments, disorders, antimicrobials, and clinical dates. The positive rates of tcdA, tcdB, and cdtA/cdtB genes were 62.9%, 63.4%, and 2.8%, respectively. The most frequent PCR ribotype was 047 (14.1%), followed by 014/0 (11.1%) and 002/0 (8.2%). In univariate analysis, the risk factors for the detection of toxin gene-positive strains in patients were older age (p = 0.0036), over ≥ 65 years old (p = 0.0175), the patients hospitalized at Department of Digestive Surgery (P = 0.0059), higher CRP level (P = 0.0395), and lower albumin level (p = 0.0014). In the multivariate analysis, the risk factor for detection of toxin gene-positive strains was the patients hospitalized at Department of Digestive Surgery (OR; 4.62, 95% CI; 1.18-18.0, p = 0.0274). In this study, the percentage of toxin gene-positive and cdtA/cdtB gene-positive strains was almost the same as that reported in previous studies, but the ribotype was different. In addition, we revealed that the risk factor associated with the detection of toxin gene-positive strains was the patients hospitalized at Department of digestive surgery.