Effective utilization of evolving methods for the laboratory diagnosis of Clostridium difficile infection

Early Economic Modeling to Inform a Target Product Profile: A Case Study of a Novel Rapid Test for Clostridioides difficile Infection

Background. Target product profiles (TPPs) specify the essential properties tests must have to be able to address an unmet clinical need. Aim. To explore how early economic modeling can help to define TPP specifications based on cost-effectiveness considerations using the example of a new rapid diagnostic for Clostridioides difficile infection (CDI), a contagious health care-associated infection causing potentially fatal diarrhea. Methods. A resource-constrained simulation model was developed to compare a hypothetical test for CDI with current practice (i.e., test with glutamate dehydrogenase enzyme immunoassay first; if positive, test with polymerase chain reaction and cytotoxicity assay) for adult individuals with suspected CDI at the Leeds Teaching Hospital National Health System (NHS) Trust in the United Kingdom. Parameters are taken from UK-based observational data collected between 2018 and 2021, published literature, and expert opinion. A methodological framework was developed 1) to derive minimum diagnostic sensitivity and specificity and maximum price for different test turnaround-time values based on cost-effectiveness considerations from the health care perspective using the National Institute of Health Care Excellence willingness-to-pay threshold of £20,000 per quality-adjusted life-years and 2) to test their robustness using a series of sensitivity analyses. Results. A new rapid test for CDI with a 15-min turnaround time would require a minimum diagnostic sensitivity and specificity both equal to 96% and a maximum price of £44 to maintain cost-effectiveness compared with standard of care. Conclusions. This study provides a framework to inform the essential test properties based on cost-effectiveness considerations and to isolate the most influential model parameters and scenarios via a series of sensitivity analyses. These specifications, in turn, could be used to inform future TPPs for tests.

Highlights

Target product profiles (TPPs) for new medical tests provide test developers with performance benchmarks and technical requirements for new tests. Early economic evaluation has already been used to identify acceptable ranges for certain performance requirements for new tests. Currently, however, early economic evaluation methods are yet to be used in the context of TPP development, and there is no guidance as to how this could and should be done.A de novo approach was developed to identify the minimum performance requirements and maximum costs for new tests, based on cost-effectiveness considerations, while also isolating most influential parameters. The added value of this framework lies in structuring early economic evaluation methods as a means of informing transparent, evidence-based minimum TPP performance specifications while also accounting as much as possible for the (inevitable) uncertainty surrounding the minimum performance requirements.This study represents the first application of early economic modeling as a means of deriving the minimum performance specifications for a novel point-of-care test for Clostridioides difficile infection as set out in a future TPP.

Concomitant Lymphocytic Colitis With Recurrent Clostridium difficile Infection

Microscopic colitis is a clinicopathological diagnosis that is characterized by chronic microscopic inflammation of the colon and presents with chronic watery diarrhea. There are following two subtypes of microscopic colitis: lymphocytic colitis and collagenous colitis. This is a case of a 70-year-old female with a history of Clostridium difficile infections who presented with persistent watery diarrhea and was diagnosed with lymphocytic colitis in the setting of a concomitant C. difficile infection. Given her clinical presentation, the patient was initiated on empiric treatment for C. difficile infection and showed a lack of clinical improvement with persistent watery diarrhea and elevated white blood cell count. The patient's symptoms resolved upon the confirmatory diagnosis and treatment of lymphocytic colitis. This study illustrates the importance of assessing for, diagnosing, and treating lymphocytic colitis in patients with chronic non-resolving watery diarrhea, especially in the setting of concomitant or recurrent C. difficile infections. Additionally, it emphasizes the need for further characterization of the relationship between C. difficile infection and microscopic colitis.

Performance of commercial PCR assays to detect toxigenic Clostridioides difficile in the feces of puppies

Clostridioides difficile is an important enteric pathogen that causes significant morbidity and mortality in humans. With community‐acquired infections on the rise, it is important to identify reservoirs of the pathogen. Companion animals can be asymptomatic carriers of C. difficile and may therefore represent a reservoir, but epidemiological studies of C. difficile within the pet‐owner unit are needed, along with validated methods to detect C. difficile in both people and animals. The goal of this study was to assess the performance of commercial qPCR assays and a multiplex PCR for C. difficile compared to toxigenic culture. These assays were tested on up to 103 fecal samples from puppies, a population in which the prevalence of C. difficile is the highest. The sensitivities, specificities, positive predictive values and negative predictive values were respectively 84.2%, 87.7%, 61.5%, and 95.9% for the Cepheid GeneXpert; 66.7%, 66.7%, 29.6%, and 90.9% for the DiaSorin Simplexa; and 94.4%, 85.0%, 65.4%, and 98.1%, for the multiplex qPCR. The agreement was highest between the GeneXpert and the multiplex PCR (90.1% agreement, with a kappa statistic of 0.77). For diagnostic purposes, the positive predictive values of the assays were low. However, the high sensitivities of the assays could render them useful for epidemiologic purposes.

Companion animals might be a reservoir of Clostridioides difficile. Diagnostic assays that are validated in both people and pets are needed to conduct epidemiological investigations within the pet‐owner unit. We found that at least one commercial PCR assay to detect C. difficile in people is also highly sensitive in dogs and could therefore be used for epidemiological purposes within the pet‐owner unit.

Real-time polymerase chain reaction (PCR) cycle threshold and Clostridioides difficile infection outcomes

OBJECTIVE

Clostridioides difficile infection (CDI) causes significant morbidity and mortality; however, the diagnosis of CDI remains controversial. The primary aim of our study was to evaluate the association of polymerase chain reaction (PCR) cycle threshold (Ct) values with CDI disease severity, recurrence, and mortality among adult patients with CDI.

DESIGN

Retrospective cohort study.

SETTING

Single tertiary-care hospital.

PATIENTS

Adult patients diagnosed with hospital-onset, healthcare facility-associated CDI from June 2014 to September 2015.

METHODS

We performed a retrospective chart review of included patients. Univariate and multivariable logistic regression methods were used to evaluate the association between Ct values and CDI severity, 8-week recurrence, and 30-day mortality.

RESULTS

Among 318 included patients, 51% were male and the mean age was 62 years; ~32% of the patients developed severe CDI and 11% developed severe-complicated CDI. The 30-day all-cause mortality rate was 11% and the 8-week recurrence rate was 9.5%. The overall mean Ct value was 32.9 (range, 23-40). Multivariable analyses showed that lower values of PCR Ct were associated with increased odds of 30-day morality (odds ratio [OR] 0.83; 95% confidence interval [CI], 0.72-0.96) but were not independently associated with CDI severity (OR, 0.99; 95% CI, 0.90-1.09) or recurrence (OR, 0.88; 95% CI, 0.77-1.00).

CONCLUSIONS

Our findings suggest that PCR Ct values at the time of diagnosis may have a limited predictive value and utility in clinical decision making for inpatients with CDI. Larger, prospective studies across different patient populations are needed to confirm our findings.

Modest Clostridiodes difficile infection prediction using machine learning models in a tertiary care hospital

Previous studies have shown promising results of machine learning (ML) models for predicting health outcomes. We develop and test ML models for predicting Clostridioides difficile infection (CDI) in hospitalized patients. This is a retrospective cohort study conducted during 2015-2017. All inpatients tested for C. difficile were included. CDI was defined as having a positive glutamate dehydrogenase and toxin results. We restricted analyses to the first record of C. difficile testing per patient. Of 3514 patients tested, 136 (4%) had CDI. Age and antibiotic use within 90 days before C. difficile testing were associated with CDI (P < 0.01). We tested 10 ML methods with and without resampling. Logistic regression, random forest and naïve Bayes models yielded the highest AUC ROC performance: 0.6. Predicting CDI was difficult in our cohort of patients tested for CDI. Multiple ML models yielded only modest results in a real-world population of hospitalized patients tested for CDI.

Incidence and Outcomes Associated With Clostridium difficile Infections: A Systematic Review and Meta-analysis

IMPORTANCE

An understanding of the incidence and outcomes of Clostridium difficile infection (CDI) in the United States can inform investments in prevention and treatment interventions.

OBJECTIVE

To quantify the incidence of CDI and its associated hospital length of stay (LOS) in the United States using a systematic literature review and meta-analysis.

DATA SOURCES

MEDLINE via Ovid, Cochrane Library Databases via Wiley, Cumulative Index of Nursing and Allied Health Complete via EBSCO Information Services, Scopus, and Web of Science were searched for studies published in the United States between 2000 and 2019 that evaluated CDI and its associated LOS.

STUDY SELECTION

Incidence data were collected only from multicenter studies that had at least 5 sites. The LOS studies were included only if they assessed postinfection LOS or used methods accounting for time to infection using a multistate model or compared propensity score-matched patients with CDI with control patients without CDI. Long-term-care facility studies were excluded. Of the 119 full-text articles, 86 studies (72.3%) met the selection criteria.

DATA EXTRACTION AND SYNTHESIS

Two independent reviewers performed the data abstraction and quality assessment. Incidence data were pooled only when the denominators used the same units (eg, patient-days). These data were pooled by summing the number of hospital-onset CDI incident cases and the denominators across studies. Random-effects models were used to obtain pooled mean differences. Heterogeneity was assessed using the I2 value. Data analysis was performed in February 2019.

MAIN OUTCOMES AND MEASURES

Incidence of CDI and CDI-associated hospital LOS in the United States.

RESULTS

When the 13 studies that evaluated incidence data in patient-days due to hospital-onset CDI were pooled, the CDI incidence rate was 8.3 cases per 10 000 patient-days. Among propensity score-matched studies (16 of 20 studies), the CDI-associated mean difference in LOS (in days) between patients with and without CDI varied from 3.0 days (95% CI, 1.44-4.63 days) to 21.6 days (95% CI, 19.29-23.90 days).

CONCLUSIONS AND RELEVANCE

Pooled estimates from currently available literature suggest that CDI is associated with a large burden on the health care system. However, these estimates should be interpreted with caution because higher-quality studies should be completed to guide future evaluations of CDI prevention and treatment interventions.

Point-of-care testing by healthcare workers for detection of meticillin-resistant Staphylococcus aureus, Clostridioides difficile, and norovirus

BACKGROUND

The feasibility of introducing three separate Cepheid GeneXpert® assays was assessed: Xpert SA Nasal Complete, Xpert C. difficile, and Xpert Norovirus for point-of-care testing (POCT) on a ward in a district general hospital.

AIM

To establish a seven-day/24 h POCT service for meticillin-resistant Staphylococcus aureus (MRSA), Clostridioides difficile, and norovirus operated solely by healthcare workers (HCWs).

METHODS

The Cepheid GeneXpert assays performance characteristics were assessed by comparing the assays to traditional central laboratory methods in terms of clinical turnaround times, hands-on time, number of process steps, time to result and diagnostic accuracy. HCW feedback was collected to consider the potential added value of applying this technology to improve patient flow and clinical care.

FINDINGS

In total 1170 tests were carried out over the 16-month study period. The assays significantly reduced hands-on time, process steps, and time to result for identification of all three micro-organisms. Overall agreement with central laboratory testing was >98% for all three assays. Staff members fed back that POCT had a positive impact in terms of clinical utility.

CONCLUSION

Xpert SA Nasal Complete for MRSA detection, Xpert C. difficile, and Xpert Norovirus can be used as POCT solely by HCWs in a ward setting. Each assay was used throughout a seven-day/24 h period with potential positive impact on bed management and patient care.

Effectiveness of a Two-Step Testing Algorithm for Reliable and Cost-Effective Detection of Clostridium difficile Infection in a Tertiary Care Hospital in Saudi Arabia

The aim of this study was to evaluate the effectiveness of a two-step algorithm for the detection of Clostridium difficile infection. Setting and Design: A two-step testing algorithm was evaluated for testing stool samples from patients suspected of Clostridium difficile infection (CDI). A total of 103 stool specimens were tested using the C. diff Quik Chek Complete enzyme immunoassay (EIA) test and the Xpert C. difficile PCR test. A two-step algorithm was implemented, and data from 3518 patient samples tested during a two-year period after implementation were analyzed to evaluate the effectiveness. The sensitivity, specificity, and positive and negative predictive values (PPV, NPV) of the Quik Chek Complete EIA test were calculated using the Xpert C. difficile PCR test as a reference method. The sensitivity, specificity, PPV, and NPV of the Quik Chek Complete EIA test for C. difficile toxin were 46.7%, 100%, 100%, and 91%, respectively. The two-step algorithm, which combined the Quik Chek Complete EIA with Xpert C. difficile PCR, improved the sensitivity and also provided rapid detection. When algorithm-based testing was performed daily, there was a 66% reduction in turnaround time compared to batch testing using a lengthy ELISA procedure. Postimplementation data analysis showed that almost 89% of the samples could be reported immediately by initial screening with Quik Chek Complete EIA. Only 11% of the samples gave discrepant results and required PCR confirmation. According to our results, the two-step algorithm is an effective tool for the rapid and reliable detection of toxigenic C. difficile from stool samples.

Evaluation of Risk Factors for Clostridium difficile Infection Based on Immunochromatography Testing and Toxigenic Culture Assay

In recent years, the diagnostic method of choice for Clostridium difficile infection (CDI) is a rapid enzyme immunoassay in which glutamate dehydrogenase (GDH) antigen and C. difficile toxin can be detected (C. diff Quik Chek Complete; Alere Inc.) (Quik Chek). However, the clinical significance remains unclear in cases that demonstrate a positive result for GDH antigen and are negative for toxin. In this study, we used the Quik Chek test kit on fecal samples, with an additional toxin detection step using a toxigenic culture assay for the aforementioned cases. CDI risk factors were assessed among the 3 groups divided by the Quik Chek test results. The study involved 1,565 fecal samples from patients suspected to have CDI who were hospitalized during the period of April 2012 to March 2014. The 3 groups were defined as follows: both GDH antigen positive and toxin positive (by Quik Chek test) (toxin-positive [TP] group, n = 109), both GDH antigen and toxin negative (toxin-negative [TN] group, n = 111), and positive only for GDH antigen but toxin positive with subsequent toxigenic culture (toxigenic culture [TC] group, n = 72). The gender, age, number of hospitalization days, white blood cell (WBC) counts, serum albumin levels, body mass index (BMI), fecal consistency, and use of antibacterials and proton pump inhibiters (PPIs) were analyzed. The positive rate for the fecal direct Quik Chek test was 7.0% (109/1,565 cases). However, toxigenic culture assays using the Quik Chek test for only the GDH-antigen-positive/toxin-negative samples were 35.3% positive (72/204 cases). As a result, the true positive rate for C. difficile toxin detection was estimated to be 11.6% (181/1,565 cases). Moreover, significant differences (P < 0.05) in the number of hospitalization days (>50 days), WBC counts (>10,000 WBCs/μl), and use of PPIs comparing the TN, TP, and TC groups, were observed. The odds ratios (ORs) for the development of CDI were 1.61 (95% confidence interval [CI], 0.94 to 2.74) and 2.98 (95% CI, 1.59 to 5.58) for numbers of hospitalization days, 2.16 (95% CI, 1.24 to 3.75) and 2.24 (95% CI, 1.21 to 4.14) for WBC counts, and 9.03 (95% CI, 4.9 to 16.6) and 9.15 (95% CI, 4.59 to 18.2) for use of PPIs in the TP and TC groups, respectively. These findings demonstrated that the use of PPIs was a significant risk factor for CDI development. Moreover, antibacterials such as carbapenems, cephalosporins, and fluoroquinolones were demonstrated to be risk factors. In conclusion, identification of the TC group of patients is thought to be important, as this study demonstrates that this group bears the same high risk of developing CDI as the TP group.

Clostridium difficile Infection in Children

Clostridium difficile is an important cause of health care associated infections. The epidemiology of C. difficile infection (CDI) in children has changed over the past few decades. There is now a higher incidence in hospitalized children, and there has been an emergence of community-onset infection. A hypervirulent strain, North American pulse type 1, has also developed. Neonates and young infants have high rates of colonization but rarely have symptoms. The well-known risk factor for CDI in children age 2 years or older is antibiotic use. Inflammatory bowel disease and cancer are associated with increased incidence and severity of CDI. Nucleic acid amplification tests are now widely used for diagnosis given their rapid turnover and higher sensitivity and specificity. The treatment for an initial episode and first recurrence is oral metronidazole. Oral vancomycin is reserved for second recurrence or severe cases. A new treatment option, fecal bowel transplant, has been reported to be safe and effective in adults, and studies are now being conducted in children. [Pediatr Ann. 2018;47(9):e359-e365.].

The Differential Diagnosis of Acute Colitis: Clues to a Specific Diagnosis

This review describes a systematic approach to the interpretation of colonic biopsy specimens of patients with acute colitis. Five main histologic patterns are discussed: acute colitis, focal active colitis, pseudomembranous colitis, hemorrhagic colitis, and ischemic colitis. For each pattern, the most common etiologic associations and their differential diagnoses are presented. Strategies based on histologic analysis and clinical considerations to differentiate acute from chronic colitides are discussed.

Interpretation and Relevance of Advanced Technique Results

Advanced techniques in the field of diagnostic microbiology have made amazing progress over the past 25 years due largely to a technological revolution in the molecular aspects of microbiology [1, 2]. In particular, rapid molecular methods for nucleic acid amplification and characterization combined with automation in the clinical microbiology laboratory as well as user-friendly software and robust laboratory informatics systems have significantly broadened the diagnostic capabilities of modern clinical microbiology laboratories. Molecular methods such as nucleic acid amplification tests (NAATs) rapidly are being developed and introduced in the clinical laboratory setting [3, 4]. Indeed, every section of the clinical microbiology laboratory, including bacteriology, mycology, mycobacteriology, parasitology, and virology, has benefited from these advanced techniques. Because of the rapid development and adaptation of these molecular techniques, the interpretation and relevance of the results produced by such molecular methods continues to lag behind. The purpose of this chapter is to review, update, and discuss the interpretation and relevance of results produced by these advanced molecular techniques.

Evaluation of the cobas Cdiff Test for Detection of Toxigenic Clostridium difficile in Stool Samples

Nucleic acid amplification tests (NAATs) are reliable tools for the detection of toxigenic Clostridium difficile from unformed (liquid or soft) stool samples. The objective of this study was to evaluate performance of the cobas Cdiff test on the cobas 4800 system using prospectively collected stool specimens from patients suspected of having C. difficile infection (CDI). The performance of the cobas Cdiff test was compared to the results of combined direct and broth-enriched toxigenic culture methods in a large, multicenter clinical trial. Additional discrepancy analysis was performed by using the Xpert C. difficile Epi test. Sample storage was evaluated by using contrived and fresh samples before and after storage at -20°C. Testing was performed on samples from 683 subjects (306 males and 377 females); 113 (16.5%) of 683 subjects were positive for toxigenic C. difficile by direct toxigenic culture, and 141 of 682 subjects were positive by using the combined direct and enriched toxigenic culture method (reference method), for a prevalence rate of 20.7%. The sensitivity and specificity of the cobas Cdiff test compared to the combined direct and enriched culture method were 92.9% (131/141; 95% confidence interval [CI], 87.4% to 96.1%) and 98.7% (534/541; 95% CI, 97.4% to 99.4%), respectively. Discrepancy analysis using results for retested samples from a second NAAT (Xpert C. difficile/Epi test; Cepheid, Sunnyvale, CA) found no false-negative and 4 false-positive cobas Cdiff test results. There was no difference in positive and negative results in comparisons of fresh and stored samples. These results support the use of the cobas Cdiff test as a robust aid in the diagnosis of CDI.

Trends in the use of laboratory tests for the diagnosis of Clostridium difficile infection and association with incidence rates in Quebec, Canada, 2010-2014

BACKGROUND

Several Clostridium difficile infection (CDI) surveillance programs do not specify laboratory strategies to use. We investigated the evolution in testing strategies used across Quebec, Canada, and its association with incidence rates.

METHODS

Cross-sectional study of 95 hospitals by surveys conducted in 2010 and in 2013-2014. The association between testing strategies and institutional CDI incidence rates was analyzed via multivariate Poisson regressions.

RESULTS

The most common assays in 2014 were toxin A/B enzyme immunoassays (EIAs) (61 institutions, 64%), glutamate dehydrogenase (GDH) EIAs (51 institutions, 53.7%), and nucleic acid amplification tests (NAATs) (34 institutions, 35.8%). The most frequent algorithm was a single-step NAAT (20 institutions, 21%). Between 2010 and 2014, 35 institutions (37%) modified their algorithm. Institutions detecting toxigenic C difficile instead of C difficile toxin increased from 14 to 37 (P < .001). Institutions detecting toxigenic C difficile had higher CDI rates (7.9 vs 6.6 per 10,000 patient days; P = .01). Institutions using single-step NAATs, GDH plus toxigenic cultures, and GDH plus cytotoxicity assays had higher CDI rates than those using an EIA-based algorithm (P < .05).

CONCLUSIONS

Laboratory detection of CDI has changed since 2010. There is an association between diagnostic algorithms and CDI incidence. Mitigation strategies are warranted.

Infection prevention and control of Clostridium difficile: a global review of guidelines, strategies, and recommendations

BACKGROUND

Clostridium difficile is the leading cause of health care-associated infections. Given the high incidence of C. difficile infection (CDI) and the lack of primary prevention through immunization, health care professionals should be aware of the most current guidance, as well as strengths and limitations of the evidence base underpinning this guidance.

METHODS

We identified publicly available national or organizational guidelines related to CDI infection and prevention control (IPC) published between 2000 and 2015 and for any health care setting through an internet search using the Google search engine. We reviewed CDI-targeted IPC recommendations and describe the assessment of evidence in available guidelines.

RESULTS

We identified documents from 28 countries/territories, mainly from acute care hospitals in North America, the Western Pacific, and Europe (18 countries). We identified only a few specific recommendations for long-term care facilities (LTCFs) and from countries in South America (Uruguay and Chile), South East Asia (Thailand), and none for Africa or Eastern Mediterranean. Of 10 IPC areas, antimicrobial stewardship was universally recognized as essential and supported by high quality evidence. Five other widely reported "strong" recommendations were: effective environment cleaning (including medical equipment), case isolation, use of personal protective equipment, surveillance, and education. Several unresolved and emerging issues were documented and currently available evidence was classified mainly as of mixed quality.

CONCLUSION

Our review underlines the need for targeted CDI IPC guidelines in several countries and for LTCFs. International harmonisation on the assessment of the evidence for best practices is needed as well as more robust evidence to support targeted recommendations.

Clostridium difficile infection: a review of current and emerging therapies

Clostridium difficile (C. difficile) infection (CDI) is the most common cause of ­healthcare-associated infections in US hospitals. The epidemic strain NAP1/BI/ribotype 027 accounts for outbreaks worldwide, with increasing mortality and severity. CDI is acquired from an endogenous source or from spores in the environment, most easily acquired during the hospital stay. The use of antimicrobials disrupts the intestinal microflora enabling C. difficile to proliferate in the colon and produce toxins. Clinical diagnosis in symptomatic patients requires toxin detection from stool specimens and rarely in combination with stool culture to increase sensitivity. However, stool culture is essential for epidemiological studies. Oral metronidazole is the recommended therapy for milder cases of CDI and oral vancomycin or fidaxomicin for more severe cases. Treatment of first recurrence involves the use of the same therapy used in the initial CDI. In the event of a second recurrence oral vancomycin often given in a tapered dose or intermittently, or fidaxomicin may be used. Fecal transplantation is playing an immense role in therapy of recurrent CDI with remarkable results. Fulminant colitis and toxic megacolon warrant surgical intervention. Novel approaches including new antibiotics and immunotherapy against CDI or its toxins appear to be of potential value.

Clostridium difficile infection: epidemiology, diagnosis and understanding transmission

Clostridium difficile infection (CDI) continues to affect patients in hospitals and communities worldwide. The spectrum of clinical disease ranges from mild diarrhoea to toxic megacolon, colonic perforation and death. However, this bacterium might also be carried asymptomatically in the gut, potentially leading to 'silent' onward transmission. Modern technologies, such as whole-genome sequencing and multi-locus variable-number tandem-repeat analysis, are helping to track C. difficile transmission across health-care facilities, countries and continents, offering the potential to illuminate previously under-recognized sources of infection. These typing strategies have also demonstrated heterogeneity in terms of CDI incidence and strain types reflecting different stages of epidemic spread. However, comparison of CDI epidemiology, particularly between countries, is challenging due to wide-ranging approaches to sampling and testing. Diagnostic strategies for C. difficile are complicated both by the wide range of bacterial targets and tests available and the need to differentiate between toxin-producing and non-toxigenic strains. Multistep diagnostic algorithms have been recommended to improve sensitivity and specificity. In this Review, we describe the latest advances in the understanding of C. difficile epidemiology, transmission and diagnosis, and discuss the effect of these developments on the clinical management of CDI.

Reducing Overutilization of Testing for Clostridium difficile Infection in a Pediatric Hospital System: A Quality Improvement Initiative

OBJECTIVES

Study objectives included addressing overuse of Clostridium difficile laboratory testing by decreasing submission rates of nondiarrheal stool specimens and specimens from children ≤12 months of age and determining resultant patient and laboratory cost savings associated with decreased testing.

METHODS

A multifaceted initiative was developed, and components included multiple provider education methods, computerized order entry modifications, and automatic declination from laboratory on testing stool specimens of nondiarrheal consistency and from children ≤12 months old. A run chart, demonstrating numbers of nondiarrheal plus infant stool specimens submitted over time, was developed to analyze the initiative's impact on clinicians' test-ordering practices. A p-chart was generated to evaluate the percentage of these submitted specimens tested biweekly over a 12-month period. Cost savings for patients and the laboratory were assessed at the study period's conclusion.

RESULTS

Run chart analysis revealed an initial shift after the interventions, suggesting a temporary decrease in testing submission; however, no sustained differences in numbers of specimens submitted biweekly were observed over time. On the p-chart, the mean percentage of specimens tested before the intervention was 100%. After the intervention, the average percentage of specimens tested dropped to 53.8%. Resultant laboratory cost savings totaled nearly $3600, and patient savings on testing charges were ∼$32 000.

CONCLUSIONS

Automatic laboratory declination of nondiarrheal stools submitted for CDI testing resulted in a sustained decrease in the number of specimens tested, resulting in significant laboratory and patient cost savings. Despite multiple educational efforts, no sustained changes in physician ordering practices were observed.

Clostridium difficile infection in patients with liver disease: a review

Over the past two decades, there has been a dramatic worldwide increase in both the incidence and severity of Clostridium difficile infection (CDI). Paralleling the increased incidence of CDI in the general population, there has been increased interest in CDI among patients with liver disease, particularly in those with liver cirrhosis and post liver transplantation. MEDLINE and several other electronic databases from January 1995 to December 2014 were searched in order to identify potentially relevant literature. Patients with cirrhosis and liver transplant recipients are at high risk for the development CDI because of antibiotics and proton pump inhibitors use, frequent and prolonged hospitalization, immunosuppressant therapy, and multiple comorbidities. Enzyme immunoassay to detect C. difficile toxins A and B in stool remains the most widely used test for CDI diagnosis, although, more recently, polymerase chain reaction (PCR)-based assays have become the preferred diagnostic test in many laboratories. Metronidazole and vancomycin, given orally, have proved to be effective in the treatment of CDI. Both cirrhotic patients and liver transplant recipients with CDI have longer length of hospital stay, increased mortality, and higher healthcare costs than those without CDI. A rapid diagnosis and adequate therapy of CDI are of paramount importance to improve liver disease patients' outcome. The aim of this review is to provide up-to-date information on the epidemiology, risk factors, pathogenesis, treatment, and outcomes in liver disease patients with CDI.

Immune-based treatment and prevention of Clostridium difficile infection

Clostridium difficile (C. difficile) causes over 500,000 infections per year in the US, with an estimated 15,000 deaths and an estimated cost of $1-3 billion. Moreover, a continual rise in the incidence of severe C. difficile infection (CDI) has been observed worldwide. Currently, standard treatment for CDI is the administration of antibiotics. While effective, these treatments do not prevent and may contribute to a disease recurrence rate of 15-35%. Prevention of recurrence is one of the most challenging aspects in the field. A better knowledge of the molecular mechanisms of the disease, the host immune response and identification of key virulence factors of C. difficilenow permits the development of immune-based therapies. Antibodies specific for C. difficile toxins have been shown to effectively treat CDI and prevent disease relapse in animal models and in humans. Vaccination has been recognized as the most cost-effective treatment/prevention for CDI. This review will summarize CDI transmission, epidemiology, major virulent factors and highlights the rational and the development of immune-based approaches against this remerging threat.

Diagnostic yields in solid organ transplant recipients admitted with diarrhea

BACKGROUND

Although diarrhea is a frequent complaint among solid organ transplant recipients, the contribution of infectious etiologies remains incompletely defined. We sought to define the etiologies of diarrhea and the yields of testing at our institution.

METHODS

We performed a retrospective analysis over an 18-month period of hospitalized solid organ transplant recipients. We stratified diarrhea by community onset vs hospital onset of diarrhea.

RESULTS

We identified 422 admissions (representing 314 unique patients) with community-onset diarrhea, and 112 admissions (representing 102 unique patients) with hospital-onset diarrhea. The majority of community- and hospital-onset diarrheal episodes had no identified etiology (60.9% and 75.9%, respectively; P = .03), yet were also self-limited (91% and 91%, respectively; P = .894). Thereafter, the most frequently encountered infectious etiologies were Clostridium difficile infection (13.3% and 11.8%, respectively), norovirus enteritis (8.2% and 3%), cytomegalovirus disease or colitis (6.3% and 2.7%), and bacterial enterocolitis (0.9% and 0%) (P = .03). In aggregate, these entities represented 93.7% and 90.5% of the identified infectious etiologies, respectively. Protozoan causes were rarely seen. Coinfection, or the simultaneous detection of ≥2 pathogens, occurred in 8 (1.9%) and 2 (1.8%) community- and hospital-onset diarrheal admissions, respectively (P = .99).

CONCLUSIONS

In solid organ transplant recipients who presented at our institution with diarrhea, approximately one-third had infectious etiologies identified, consisting predominantly of C. difficile, norovirus, cytomegalovirus, and bacterial enterocolitis. Other infectious etiologies were rare.

Incidence of polymerase chain reaction-diagnosed Clostridium difficile in a large high-risk cohort, 2011-2012

OBJECTIVE

To describe incidence rates (IRs) of polymerase chain reaction (PCR)-diagnosed Clostridium difficile infection (CDI) in a large high-risk cohort.

PATIENTS AND METHODS

Members of Kaiser Permanente Southern California 1 year or older who were admitted to any of 14 Kaiser Permanente hospitals from January 1, 2011, through December 31, 2012, were included in the study. The CDI cases were identified by PCR in the inpatient and outpatient settings. The CDI IRs per 10,000 inpatient-days are estimated by year, surveillance category, age, sex, race/ethnicity, and Charlson comorbidity index. Recurrence rates are presented by age, sex, and race/ethnicity. Death and colectomy in the 30 days after CDI diagnosis, white blood cell count, and serum creatinine level are assessed.

RESULTS

Among 268,655 patients, 4286 (1.6%) had CDI. Among these patients, 671 (15.7%) had recurrent infections. The IR was highest among community-onset, health care facility-associated infections (11.1 per 10,000 inpatient-days). The CDI IRs differed by age, sex, and race/ethnicity. Overall, 528 patients (12.3%) died within 30 days of a positive CDI test result. The CDI IRs increased 34% with implementation of PCR testing.

CONCLUSION

Increasingly, PCR is being used because of its higher diagnostic sensitivity. Reassessing the epidemic using PCR updates our understanding of CDI risk. Our capacity to identify patients presenting in the outpatient setting after discharge provides a more accurate picture of health care-associated CDI rates, particularly because the community appears to assume an increasing role in CDI onset and possibly transmission. The CDI burden differs by race, comorbidity, sex, and previous health care use. The detected increase in CDI incidence after transitioning to PCR diagnosis was modest compared with previous studies.

Vaccines against Clostridium difficile

Clostridium difficile infection (CDI) is recognized as a major cause of nosocomial diseases ranging from antibiotic related diarrhea to fulminant colitis. Emergence during the last 2 decades of C. difficile strains associated with high incidence, severity and lethal outcomes has increased the challenges for CDI treatment. A limited number of drugs have proven to be effective against CDI and concerns about antibiotic resistance as well as recurring disease solicited the search for novel therapeutic strategies. Active vaccination provides the attractive opportunity to prevent CDI, and intense research in recent years led to development of experimental vaccines, 3 of which are currently under clinical evaluation. This review summarizes recent achievements and remaining challenges in the field of C. difficile vaccines, and discusses future perspectives in view of newly-identified candidate antigens.

Evaluation of the diagnostic performance of the xpert Clostridium difficile assay and its comparison with the toxin A/B enzyme-linked fluorescent assay and in-house real-time PCR assay used for the detection of toxigenic C. difficile

BACKGROUND

Clostridium difficile genes or toxin can be detected using several laboratory techniques. In this study, we compared the performance of the Xpert C. difficile assay with that of a toxin A/B enzyme-linked fluorescent immunoassay (ELFA) and an in-house real-time PCR assay for the tcdB gene.

METHODS

From April 2011 through January 2012, 138 soft or liquid stool samples from 138 adult patients at Paik Hospital were tested using the toxin A/B ELFA, in-house real-time PCR assay, and Xpert C. difficile assay to detect toxigenic C. difficile. Specimens were considered true positives if results were positive in both the in-house real-time PCR for tcdB gene and Xpert C. difficile assays.

RESULTS

Sensitivity of the toxin A/B ELFA, in-house tcdB gene real-time PCR, and Xpert C. difficile assay were 67.6%, 97.3%, and 100.0%, respectively. The specificity of the in-house tcdB gene real-time PCR assay was 100%, while the specificity was 98.0% for the other two methods. The turnaround time (TAT) was 50 min for the Xpert C. difficile assay, 75 min for the toxin A/B ELFA, and 160 min for the in-house real-time PCR assay.

CONCLUSION

The Xpert C. difficile assay and the in-house real-time PCR assay had higher sensitivity than the toxin A/B ELFA; however, the specificities of the three assays were similar. Considering its rapid TAT and high sensitivity, use of the Xpert C. difficile assay is highly recommended for rapid and accurate diagnosis of C. difficile infection.

Clostridium difficile and inflammatory bowel disease: Role in pathogenesis and implications in treatment

Clostridium difficile (C. difficile) is the leading cause of antibiotic associated colitis and nosocomial diarrhea. Patients with inflammatory bowel disease (IBD) are at increased risk of developing C. difficile infection (CDI), have worse outcomes of CDI-including higher rates of colectomy and death, and experience higher rates of recurrence. However, it is still not clear whether C. difficile is a cause of IBD or a consequence of the inflammatory state in the intestinal environment. The burden of CDI has increased dramatically over the past decade, with severe outbreaks described in many countries, which have been attributed to a new and more virulent strain. A parallel rise in the incidence of CDI has been noted in patients with IBD. IBD patients with CDI tend be younger, have less prior antibiotic exposure, and most cases of CDI in these patients represent outpatient acquired infections. The clinical presentation of CDI in these patients can be unique-including diversion colitis, enteritis and pouchitis, and typical findings on colonoscopy are often absent. Due to the high prevalence of CDI in patients hospitalized with an IBD exacerbation, and the prognostic implications of CDI in these patients, it is recommended to test all IBD patients hospitalized with a disease flare for C. difficile. Treatment includes general measures such as supportive care and infection control measures. Antibiotic therapy with either oral metronidazole, vancomycin, or the novel antibiotic-fidaxomicin, should be initiated as soon as possible. Fecal macrobiota transplantation constitutes another optional treatment for severe/recurrent CDI. The aim of this paper is to review recent data on CDI in IBD: role in pathogenesis, diagnostic methods, optional treatments, and outcomes of these patients.

Correlation between Clostridium difficile bacterial load, commercial real-time PCR cycle thresholds, and results of diagnostic tests based on enzyme immunoassay and cell culture cytotoxicity assay

The impact of Clostridium difficile fecal loads on diagnostic test results is poorly understood, but it may have clinical importance. In this study, we investigated the relationship between C. difficile fecal load and the results of four assays: a glutamate dehydrogenase (GDH) enzyme immunoassay (EIA), a toxin A/B antigen EIA (ToxAB), a cell culture cytotoxicity assay (CCA), and PCR targeting the tcdB gene. We also compared the PCR cycle threshold (CT) with the results of quantitative culture using Spearman's rank correlation coefficient. Finally, we sequenced the genomes of 24 strains with different detection profiles. A total of 203 clinical samples harboring toxigenic C. difficile were analyzed and sorted into one of four groups: 17 PCR(+) (group 1), 37 PCR(+) GDH(+) (group 2), 24 PCR(+) GDH(+) CCA(+) (group 3), and 125 PCR(+) GDH(+) ToxAB(+) (group 4). The overall median fecal load in log10 CFU/g was 6.67 (interquartile range [IQR], 5.57 to 7.54). The median fecal bacterial load of groups 1, 2, 3, and 4 were 4.15 (IQR, 3.00 to 4.98), 5.74 (IQR, 4.75 to 6.16), 6.20 (IQR, 5.23 to 6.80), and 7.08 (IQR, 6.35 to 7.83), respectively. Group 1 samples had lower fecal loads than those from each of the other groups (P < 0.001). Group 2 samples had lower fecal loads than those from groups 3 and 4 (P < 0.001). There was a significant correlation between PCR CT and fecal loads (ρ = -0.697; P < 0.001). NAP1 strains were associated with the detection of toxins by EIA or CCA (P = 0.041). This study demonstrates an association between C. difficile fecal load and the results of routinely used diagnostic tests.

Clostridium difficile infection in patients with inflammatory bowel disease: An update

Inflammatory bowel disease (IBD) has many etiological factors, among which microbial factors have attracted more and more attention recently. Studies have demonstrated that the incidence of Clostridium difficile infection (CDI) in both adult and children IBD patients has been rising in recent years. Many drugs such as antibiotics, immunosuppressive agents, and acid-suppressing agents may increase the incidence of CDI. Identifying CDI and selecting effective antibiotics are keys to successful treatment, and immunological and ecological treatments are also useful choices. In this article, we will review the progress in research of CDI in IBD patients.

Overcoming barriers to effective recognition and diagnosis of Clostridium difficile infection

With the frequency of cases of Clostridium difficile infection (CDI) increasing in many developed countries, accurate and reliable laboratory diagnosis of CDI is more important than ever. However, the diagnosis of CDI has been handicapped by the existence of two reference standards, one of which detects C. difficile toxin (cytotoxin assay) and the other only toxigenic strains (cytotoxigenic culture). Being relatively slow and laborious to perform, these reference methods were largely abandoned as routine diagnostic methods for toxin detection in favour of stand-alone rapid enzyme immunoassays (EIAs), which have suboptimal sensitivity and specificity. The management of CDI is undermined by high rates of both false-positive and false-negative test results. More recently developed nucleic acid amplification tests (NAATs) for toxin gene detection offer improved sensitivity over immunoassays, but fail to discriminate between CDI and asymptomatic colonization with C. difficile, and have clear drawbacks as stand-alone diagnostic tests. Two-step or three-step diagnostic algorithms have been proposed as a solution. In a large study of the effectiveness of currently available tests, a diagnostic algorithm was developed that combines available tests to more effectively distinguish patients with CDI from uninfected patients. This two-test protocol, which is now used in National Health Service laboratories in England, comprises an EIA for glutamate dehydrogenase detection or NAATs for toxin gene detection, followed by a relatively sensitive toxin EIA. This algorithm also identifies 'potential C. difficile excretors', individuals with diarrhoeal samples that contain C. difficile but without demonstrable toxin, who may be a source of transmission of C. difficile to susceptible patients.

Interpretation and Relevance of Advanced Technique Results

Advanced techniques in the field of diagnostic microbiology have made amazing progress over the past two decades due largely to a technological revolution in the molecular aspects of microbiology [1, 2]. In particular, rapid molecular methods for nucleic acid amplification and characterization combined with automation and user-friendly software have significantly broadened the diagnostic capabilities of modern clinical microbiology laboratories. Molecular methods such as nucleic acid amplification tests (NAATs) rapidly are being developed and introduced in the clinical laboratory setting. Indeed, every section of the clinical microbiology laboratory, including bacteriology, mycology, mycobacteriology, parasitology, and virology, have benefited from these advanced techniques. Because of the rapid development and adaptation of these molecular techniques, the interpretation and relevance of the results produced by such molecular methods has lagged somewhat behind. The purpose of this chapter is to review and discuss the interpretation and relevance of results produced by these advanced molecular techniques. Moreover, this chapter will address the “myths” of NAATs, as these myths can markedly influence the interpretation and relevance of these results.

Clostridium difficile infection in the inflammatory bowel disease patient

Clostridium difficile infection (CDI) has been increasing in frequency and severity in patients with inflammatory bowel disease (IBD). Population based and single center studies have shown worse clinical outcomes in concomitant CDI and IBD, with several reporting longer length of hospital stay, higher colectomy rates and increased mortality. Clinically, CDI may be difficult to distinguish from an IBD flare and may range from an asymptomatic carrier state to severe life threatening colitis. The traditional risk factors for CDI have included hospitalization, antibiotic use, older age and severe co-morbid disease but IBD patients have several distinct characteristics including younger age, community acquisition, lack of antibiotic exposure, colonic IBD and steroid use. CDI can occur in the small bowel and specifically in ulcerative colitis patients who have had a colectomy and an ileal pouch anal anastomosis. PCR based assays and combination Elisa algorithms have improved the sensitivity and specificity of testing, though in IBD patients have raised clinical questions about how to best manage diarrhea in the setting of possible C. difficile colonization. Treatment modalities for CDI have not been examined in randomized clinical trials in the IBD population. Newer antibiotics, immunotherapy and fecal microbiota transplantation may alter current treatment strategies. This review will focus on the unique epidemiology of CDI in IBD patients, detail clinical disease states, and provide updated diagnostic strategies, prevention and treatment options.

Evaluation of Clostridium difficile fecal load and limit of detection during a prospective comparison of two molecular tests, the illumigene C. difficile and Xpert C. difficile/Epi tests

In a large prospective comparison, the illumigene test detected Clostridium difficile in 98% of toxin-positive and 58% of toxin-negative samples confirmed positive by other methods. The Xpert was uniformly sensitive. Most samples with discrepant results had C. difficile concentrations below the illumigene limit of detection. The significance of low-level C. difficile detection needs investigation.

Using a dog's superior olfactory sensitivity to identify Clostridium difficile in stools and patients: proof of principle study

OBJECTIVE

To investigate whether a dog's superior olfactory sensitivity can be used to detect Clostridium difficile in stool samples and hospital patients.

DESIGN

Proof of principle study, using a case-control design.

SETTING

Two large Dutch teaching hospitals.

PARTICIPANTS

A 2 year old beagle trained to identify the smell of C difficile and tested on 300 patients (30 with C difficile infection and 270 controls).

INTERVENTION

The dog was guided along the wards by its trainer, who was blinded to the participants' infection status. Each detection round concerned 10 patients (one case and nine controls). The dog was trained to sit or lie down when C difficile was detected.

MAIN OUTCOME MEASURES

Sensitivity and specificity for detection of C difficile in stool samples and in patients.

RESULTS

The dog's sensitivity and specificity for identifying C difficile in stool samples were both 100% (95% confidence interval 91% to 100%). During the detection rounds, the dog correctly identified 25 of the 30 cases (sensitivity 83%, 65% to 94%) and 265 of the 270 controls (specificity 98%, 95% to 99%).

CONCLUSION

A trained dog was able to detect C difficile with high estimated sensitivity and specificity, both in stool samples and in hospital patients infected with C difficile.

Outcomes in patients tested for Clostridium difficile toxins

Clostridium difficile testing is shifting from toxin detection to C. difficile detection. Yet, up to 60% of patients with C. difficile by culture test negative for toxins and it is unclear whether they are infected or carriers. We reviewed medical records for 7046 inpatients with a C. difficile toxin test from 2005 to 2009 to determine the duration of diarrhea and rate of complications and mortality among toxin-positive (toxin+) and toxin- patients. Overall, toxin- patients had less severe diarrhea, fewer diarrhea days, and lower mortality (P < 0.001, all comparisons) than toxin+ patients. One toxin- patient (n = 1/6121; 0.02%) was diagnosed with pseudomembranous colitis, but there were no complications such as megacolon or colectomy for fulminant CDI among toxin- patients. These data suggest that C. difficile-attributable complications are rare among patients testing negative for C. difficile toxins. More studies are needed to evaluate the clinical significance of C. difficile detection in toxin- patients.

Consequences of Clostridium difficile infection: understanding the healthcare burden

Clostridium difficile is the leading cause of infectious nosocomial diarrhoea in developed countries, with a measured incidence of approximately five episodes per 10,000 days of hospital stay in Europe. Accurate diagnosis of C. difficile infection (CDI) is a prerequisite for obtaining reliable epidemiological data, but in many European countries diagnosis is probably suboptimal. A significant percentage of CDI cases are missed because clinicians often fail to request tests for C. difficile toxins in cases of unexplained diarrhoea. In addition, some laboratories continue to use tests of low sensitivity or apply them inappropriately. In one study in Spain, failure to request CDI testing in more than two-thirds of patients with unexplained diarrhoea led to significant underdiagnosis of cases. A recent pan-European survey revealed huge discrepancies in the rate of CDI testing across Europe, which suggests that epidemiological reports underestimate the true incidence of CDI in many parts of Europe. This is important because, as this review of the clinical and economic burden of CDI illustrates, infection with C. difficile imposes a significant burden not only on patients, owing to increased morbidity and mortality, but also on healthcare systems and society in general. On the basis of current incidence rates, annual costs for management of CDI amount to approximately $800 million in the USA and €3000 million in Europe. Moreover, estimates suggest that costs associated with recurrent CDI can exceed those of primary CDI. Measures to more effectively prevent CDI and reduce CDI recurrence rates may help to reduce this burden.

An evaluation of repeat stool testing for Clostridium difficile infection by polymerase chain reaction

GOALS

To evaluate the yield of repeat stool polymerase chain reaction (PCR) testing in patients with suspected Clostridium difficile infection (CDI).

BACKGROUND

CDI is a major challenge in health care due to its frequent occurrence and high associated costs. Enzyme immunoassay and PCR are commonly performed diagnostic tests for CDI.

METHODS

Our microbiology laboratory database was queried from January 1, 2008 to June 30, 2010 for all patients who underwent PCR stool testing for suspected CDI. Data collected included age, sex, number of stool tests performed within a 14-day period after the first test, and location of patient (inpatient vs. outpatient). Analyses were performed using JMP version 9.0.1.

RESULTS

PCR testing was performed in 15,515 patients. The median age was 58.3 years (range, 10 d to 104.3 y) and 46.2% of patients were women. Repeat testing was infrequent; 87.3% of patients had testing performed only once in a 14-day period. Increased age, male sex, and inpatient location were predictors of repeat testing. The median time between an initial test and the first repeat test was 5 days. After an initial negative test, the percentage of patients having a subsequent positive test was low (2.7% in 7 d and 3.2% in 14 d). The percentage of repeat tests that was positive within 7 days (2.9%) was lower than the percentage that was positive from day 8 to day 14 (4.8%, P=0.05).

CONCLUSIONS

Repeat testing for C. difficile has a low yield, and patients with an initial negative test should not routinely be retested.

Clostridium difficile infection: new insights into management

Clostridium difficile was first described as a cause of diarrhea in 1978 and is now among the leading 3 hospital-acquired infections in the United States, along with methicillin-resistant Staphylococcus aureus and vancomycin-resistant enterococci. In the past 2 decades, there has been an increase in the incidence, severity, and recurrence rates of C difficile infection, all of which are associated with poor outcomes. In addition, several novel risk factors and newer treatment methods are emerging, including fidaxomicin therapy, treatment using monoclonal antibodies, and fecal microbiota transplantation, that have shown promise for the treatment of C difficile infection. This review focuses on the changing epidemiology, risk factors, and newer methods for treatment of C difficile infection.

Impact of the type of diagnostic assay on Clostridium difficile infection and complication rates in a mandatory reporting program

BACKGROUND

Most Clostridium difficile infection (CDI) surveillance programs neither specify the diagnostic method to be used nor stratify rates accordingly. We assessed the difference in healthcare-associated CDI (HA-CDI) incidence and complication rates obtained by 2 validated diagnostic methods.

METHODS

This was a prospective cohort study of patients for whom a C. difficile test was ordered between 1 August 2010 and 31 July 2011. All specimens were tested in parallel by a commercial polymerase chain reaction (PCR) assay targeting toxin B gene tcdB, and a 3-step algorithm detecting glutamate dehydrogenase and toxins A and B by enzyme immunoassay and cell culture cytotoxicity assay (EIA/CCA). CDI incidence rate ratios were calculated using univariate Poisson regression.

RESULTS

A total of 1321 stool samples were tested during a period totaling 95 750 patient-days. Eighty-five HA-CDI cases were detected by PCR and 56 cases by EIA/CCA (P = .01). The overall incidence rate was 8.9 per 10 000 patient-days (95% confidence interval [CI], 7.1-10.9) by PCR and 5.8 per 10 000 patient-days (95% CI, 4.4-7.4) by EIA/CCA (P = .01). The incidence rate ratio comparing PCR and EIA/CCA was 1.52 (95% CI, 1.08-2.13; P = .015). Overall complication rate was 27% (23/85) when CDI was diagnosed by PCR and 39% (22/56) by EIA/CCA (P = .16). Cases detected by PCR only were less likely to develop a complication of CDI compared with cases detected by both PCR and EIA/CCA (3% vs 39%, respectively; P < .001).

CONCLUSIONS

Performing PCR instead of EIA/CCA is associated with a >50% increase in the CDI incidence rate. Standardization of diagnostic methods may be indicated to improve interhospital comparison.

Comparison of BD GeneOhm Cdiff and Seegene Seeplex ACE PCR assays using toxigenic Clostridium difficile culture for direct detection of tcdB from stool specimens

We evaluated the performances of 2 PCR assays (BD GeneOhm and Seegene ACE) for direct detection of tcdB from stool specimens. The concordance rate between BD and Seegene was 96.3%. The sensitivities, specificities, positive predictive values (PPVs), and negative predictive values (NPVs) of BD and Seegene were 95.7%, 96.5%, 91.8%, and 98.2% and 90.0%, 97.1%, 92.6%, and 96.0%, respectively.

Role of fecal Clostridium difficile load in discrepancies between toxin tests and PCR: is quantitation the next step in C. difficile testing?

Direct tests for Clostridium difficile are 30-50 % more sensitive than tests for C. difficile toxins but the reasons for this discrepancy are incompletely understood. In addition to toxin degradation and strain differences, we hypothesized that C. difficile concentration could be important in determining whether toxins are detected in fecal samples. We performed standard curves on an FDA-approved real-time PCR test for the C. difficile tcdB gene (Xpert C. difficile/Epi, Cepheid) during a prospective comparison of a toxin immunoassay (Meridian Premier), PCR and toxigenic culture. Immunoassay-negative, PCR-positive samples were retested with a cell cytotoxin assay (TechLab). Among 107 PCR-positive samples, 46 (43.0 %) had toxins detected by immunoassay and an additional 18 (16.8 %) had toxin detected by the cytotoxin assay yielding 64 (59.8 %) toxin-positive and 43 (40.2 %) toxin-negative samples. Overall, toxin-negative samples with C. difficile had 10(1)-10(4) fewer DNA copies than toxin-positive samples and most discrepancies between toxin tests and PCR were associated with a significant difference in C. difficile quantity. Of the toxin-positive samples, 95 % had ≥ 4.1 log(10) C. difficile tcdB DNA copies/mL; 52 % of immunoassay-negative samples and 70 % of immunoassay and cytotoxin negative samples had <4.1 log(10) C. difficile tcdB DNA copies/mL. These findings suggest that fecal C. difficile concentration is a major determinant of toxin detection and C. difficile quantitation may add to the diagnostic value of existing test methods. Future studies are needed to validate the utility of quantitation and determine the significance of low concentrations of C. difficile in the absence of detectable toxin.

Molecular techniques for diagnosis of Clostridium difficile infection: systematic review and meta-analysis

OBJECTIVE

To assess the usefulness of 2 rapid molecular diagnostic techniques, polymerase chain reaction (PCR) and loop-mediated isothermal amplification (LAMP), in Clostridium difficile infection (CDI).

METHODS

We conducted a systematic review and meta-analysis to evaluate the accuracy of PCR and LAMP in diagnosis of CDI, including studies that used toxigenic culture or cytotoxicity assay as reference standard.

RESULTS

A search of PubMed and CinAHL medical databases yielded 25 PCR studies, including 11,801 samples that met inclusion criteria and 6 heterogeneous studies that evaluated LAMP. With toxigenic culture as a standard, pooled sensitivity was 0.92 (95% confidence interval [CI], 0.91-0.94); specificity, 0.94 (95% CI, 0.94-0.95); and diagnostic odds ratio, 378 (95% CI, 260-547). With cytotoxicity as a standard, pooled sensitivity was 0.87 (95% CI, 0.84-0.90); specificity, 0.97 (95% CI, 0.97-0.98); and diagnostic odds ratio, 370 (95% CI, 226-606).

CONCLUSION

Polymerase chain reaction is a highly accurate test for identifying CDI. Heterogeneity in LAMP studies did not allow meta-analysis; however, further research into this promising method is warranted.

Evaluation of three enzyme immunoassays and a loop-mediated isothermal amplification test for the laboratory diagnosis of Clostridium difficile infection

The laboratory diagnosis of Clostridium difficile infection (CDI) consists of the detection of toxigenic Clostridium difficile, and/or its toxins A or B in stool preferably in a two-step algorithm. In a prospective study, we compared the performance of three toxin enzyme immunoassays (EIAs)-ImmunoCard Toxins A & B, Premier Toxins A & B and C. diff Quik Chek Complete, which combines a toxins test and a glutamate dehydrogenase (GDH) antigen EIA in one device -and the loop-mediated isothermal amplification assay Illumigene C. difficile. In total 986 stool samples were analyzed. Compared with toxigenic culture as the gold standard, sensitivities, specificities, PPV and NPV values of the toxin EIAs were 41.1-54.8 %, 98.9-100 %, 75.0-100 % and 95.5-96.5 % respectively, of the Illumigene assay 93.3 %, 99.7 %, 95.8 % and 99.5 %. Illumigene assays performed significantly better for non-014/020 PCR-ribotypes than for C. difficile isolates belonging to 014/020. Discrepant analysis of three culture-negative, but Illumigene-positive samples, revealed the presence of toxin genes using real-time PCRs. In addition to the GDH EIA (NPV of 99.8 %), the performance of Illumigene allows this test to be introduced as a first screening test for CDI- or as a confirmation test for GDH -positive samples, although the initial invalid Illumigene result of 4.4 % is a point of concern.

Detection, treatment, and prevention of Clostridium difficile infection

Clostridium difficile is a gram-positive anaerobic bacillus responsible for approximately 1 of 5 cases of antibiotic-associated diarrhea. C difficile infection (CDI) is defined by at least 3 unformed stools in a 24-hour period and stool, endoscopic, or histopathologic test results that indicate the presence of this bacteria. The history of CDI research can be divided into early (before 2000) and modern eras (after 2000). C difficile was first described in 1935, and the characteristics and causes of CDI as well as therapies were identified during the early era of research. During the modern era, CDI has become a more common, aggressive nosocomial infection. Our understanding of the epidemiology, diagnosis, treatment, and prevention of CDI has increased at a rapid pace. We review features of CDI diagnosis, treatment, and prevention.