We compared the Qiagen artus C. difficile QS-RGQ kit, a new nucleic acid amplification test for the detection of Clostridium difficile toxins in stool specimens, with the Cepheid Xpert C. difficile test. The sensitivity, specificity, positive predictive value, and negative predictive value for the Qiagen artus C. difficile QS-RGQ test were 100%, 89.5%, 60.9%, and 100%, and those for the Cepheid Xpert C. difficile test were 100%, 90%, 62.2%, and 100%, respectively.
The Becton Dickinson (BD) PCR-based GeneOhm Cdiff assay has demonstrated a high sensitivity and specificity for detecting Clostridium difficile. Recently, the BD Max platform, using the same principles as BD GeneOhm, has become available in Australia. This study aimed to investigate the sensitivity and specificity of BD Max Cdiff assay for the detection of toxigenic C. difficile in an Australian setting. Between December 2013 and January 2014, 406 stool specimens from 349 patients were analysed with the BD Max Cdiff assay. Direct and enrichment toxigenic culture were performed on bioMérieux ChromID C. difficile agar as a reference method. isolates from specimens with discrepant results were further analysed with an in-house PCR to detect the presence of toxin genes. The overall prevalence of toxigenic C. difficile was 7.2%. Concordance between the BD Max assay and enrichment culture was 98.5%. The sensitivity, specificity, positive predictive value and negative predictive value for the BD Max Cdiff assay were 95.5%, 99.0%, 87.5% and 99.7%, respectively, when compared to direct culture, and 91.7%, 99.0%, 88.0% and 99.4%, respectively, when compared to enrichment culture. The new BD Max Cdiff assay appeared to be an excellent platform for rapid and accurate detection of toxigenic C. difficile.
Se compararon dos algoritmos de diagnóstico de varios pasos basado en C. Difficile Quik Chek completa y, como pruebas confirmatorias, Genomera C. difficile y Xpert C. difficile. La sensibilidad, especificidad, valor predictivo positivo y valor predictivo negativo fueron 87,2%, 99,7%, 97,1% y 98,3%, respectivamente, para el algoritmo basado en Genomera y 89.7%, 99.4%, 95.5% y 98.6%, respectivamente , para el algoritmo basado en Xpert. Genomera representa una alternativa a la Xpert como prueba confirmatoria de un algoritmo de múltiples pasos para la infección por Clostridium difficile diagnóstico (CDI).
The diagnosis of Clostridium difficile infection (CDI) requires the detection of toxigenic C. difficile or its toxins and a clinical assessment. We evaluated the performance of four nucleic acid amplification tests (NAATs) detecting toxigenic C. difficile directly from faeces compared to routine toxigenic culture. In total, 300 faecal samples from Danish hospitalised patients with diarrhoea were included consecutively. Culture was performed in duplicate (routine and 'expanded toxigenic culture': prolonged and/or re-culture) and genotypic toxin profiling by polymerase chain reaction (PCR), PCR ribotyping and toxinotyping (TT) were performed on culture-positive samples. In parallel, the samples were analysed by four NAATs; two targeting tcdA or tcdB (illumigene C. difficile and PCRFast C. difficile A/B) and two multi-target real-time (RT) PCR assays also targeting cdt and tcdC alleles characteristic of epidemic and potentially more virulent PCR ribotypes 027, 066 and 078 (GeneXpert C. difficile/Epi and an 'in-house RT PCR' two-step algorithm). The multi-target assays were significantly more sensitive compared to routine toxigenic culture (p < 0.05) and significantly more robust to inhibition compared to PCRFast (p < 0.001). Duplicate 'expanded toxigenic culture' increased the culture-positive rate by 29% compared to routine culture. The ability of the GeneXpert and in-house assays to correctly classify PCR ribotype 027 was high (>95%), and in-house PCR displayed 100% correct identification of PCR ribotypes 066 and 078. Furthermore, the presence of the PCR enhancer bovine serum albumin (BSA) was found to be related to high sensitivity and low inhibition rate. Rapid laboratory diagnosis of toxigenic C. difficile by RT PCR was accurate.
Clostridium difficile is a Gram-positive bacterium commonly found in health care and long-term-care facilities and is the most common cause of antibiotic-associated diarrhea. Rapid detection of this bacterium can assist physicians in implementing contact precautions and appropriate antibiotic therapy in a timely manner. The purpose of this study was to compare the clinical performance of the Quidel Lyra Direct C. difficile assay (Lyra assay) (Quidel, San Diego, CA) to that of a direct cell culture cytotoxicity neutralization assay (CCNA) and enhanced toxigenic culture. This study was performed at three geographically diverse laboratories within the United States using residual stool specimens submitted for routine C. difficile testing. Residual samples were tested using the Lyra assay on three real-time PCR platforms, and results were compared to those for direct CCNA and enhanced toxigenic culture. The test results for all platforms were consistent across all three test sites. The sensitivity and specificity of the Lyra assay on the SmartCycler II, ABI 7500 Fast DX, and ABI QuantStudio DX instruments compared to CCNA were 90.0% and 93.3%, 95.0% and 94.2%, and 93.8% and 95.0%, respectively. Compared to enhanced toxigenic culture, the sensitivity and specificity of the Lyra assay on the SmartCycler II, ABI 7500, and QuantStudio instruments were 82.1% and 96.9%, 89.3% and 98.8%, and 85.7% and 99.0%, respectively. Overall, the Lyra assay is easy to use and versatile and compares well to C. difficile culture methods.
Here we describe a method for the detection of Clostridium difficile from stool using a novel low-complexity and rapid extraction process called Heat Elution (HE). The HE method is two-step and takes just 10 minutes, no specialist instruments are required and there is minimal hands-on time. A test method using HE was developed in conjunction with Loop-mediated Isothermal Amplification (LAMP) combined with the real-time bioluminescent reporter system known as BART targeting the toxin B gene (tcdB). The HE-LAMP-BART method was evaluated in a pilot study on clinical fecal samples (tcdB(+), n = 111; tcdB(-), n= 107). The HE-LAMP-BART method showed 95.5% sensitivity and 100% specificity against a gold standard reference method using cytotoxigenic culture and also a silica-based robotic extraction followed by tcdB PCR to control for storage. From sample to result, the HE-LAMP-BART method typically took 50 minutes, whereas the PCR method took >2.5 hours. In a further study (tcdB(+), n = 47; tcdB(-), n= 28) HE-LAMP-BART was compared to an alternative commercially available LAMP-based method, Illumigene (Meridian Bioscience, OH), and yielded 87.2% sensitivity and 100% specificity for the HE-LAMP-BART method compared to 76.6% and 100%, respectively, for Illumigene against the reference method. A subset of 27 samples (tcdB(+), n = 25; tcdB(-), n= 2) were further compared between HE-LAMP-BART, Illumigene, GeneXpert (Cepheid, Sunnyvale, CA) and RIDA®QUICK C. difficile Toxin A/B lateral flow rapid test (R-Biopharm, Darmstadt, Germany) resulting in sensitivities of HE-LAMP-BART 92%, Illumigene 72% GeneXpert 96% and RIDAQuick 76% against the reference method. The HE-LAMP-BART method offers the advantages of molecular based approaches without the cost and complexity usually associated with molecular tests. Further, the rapid time-to-result and simple protocol means the method can be applied away from the centralized laboratory settings.
The analytical performance and cost-effectiveness of the Wampole Toxin A/B EIA, the C. Diff. Quik Chek Complete (CdQCC) (a combined glutamate dehydrogenase antigen/toxin enzyme immunoassay), two RT-PCR assays (Progastro Cd and BD GeneOhm) and a modified two-step algorithm using the CdQCC reflexed to RT-PCR for indeterminate results were compared. The sensitivity of the Wampole Toxin A/B EIA, CdQCC (GDH antigen), BD GeneOhm and Progastro Cd RT-PCR were 85.4%, 95.8%, 100% and 93.8%, respectively. The algorithm provided rapid results for 86% of specimens and the remaining indeterminate results were resolved by RT-PCR, offering the best balance of sensitivity and cost savings per test (algorithm ∼US$13.50/test versus upfront RT-PCR ∼US$26.00/test).
Simplexa Clostridium difficile universal direct PCR, a real-time PCR assay for the detection of the C. difficile toxin B (tcdB) gene using the 3M integrated cycler, was compared with a two-step algorithm which includes the C. Diff Chek-60 glutamate dehydrogenase (GDH) antigen assay followed by cytotoxin neutralization. Three hundred forty-two liquid or semisolid stools submitted for diagnostic C. difficile testing, 171 GDH antigen positive and 171 GDH antigen negative, were selected for the study. All samples were tested by the C. Diff Chek-60 GDH antigen assay, cytotoxin neutralization, and Simplexa direct PCR. Of 171 GDH-positive samples, 4 were excluded (from patients on therapy or from whom duplicate samples were obtained) and 88 were determined to be true positives for toxigenic C. difficile. Of the 88, 67 (76.1%) were positive by the two-step method and 86 (97.7%) were positive by PCR. Seventy-nine were positive by the GDH antigen assay only. Of 171 GDH antigen-negative samples, none were positive by PCR. One antigen-negative sample positive by the cytotoxin assay only was deemed a false positive based on chart review. Simplexa C. difficile universal direct PCR was significantly more sensitive for detecting toxigenic C. difficile bacteria than cytotoxin neutralization (P = 0.0002). However, most PCR-positive/cytotoxin-negative patients did not have clear C. difficile disease. The estimated cost avoidance provided by a more rapid molecular diagnosis was outweighed by the cost of isolating and treating PCR-positive/cytotoxin-negative patients. The costs, clinical consequences, and impact on nosocomial transmission of treating and/or isolating patients positive for toxigenic C. difficile by PCR but negative for in vivo toxin production merit further study.
INTRODUCTION: Despite the known importance of Clostridium difficile as a nosocomial pathogen, few studies regarding Clostridium difficile infection (CDI) in Brazil have been conducted. To date, the diagnostic tests that are available on the Brazilian market for the diagnosis of CDI have not been evaluated. The aim of this study was to compare the performances of four commercial methods for the diagnosis of CDI in patients from a university hospital in Brazil.
METHODS: Three enzyme immunoassays (EIAs) and one nucleic acid amplification test (NAAT) were evaluated against a cytotoxicity assay (CTA) and toxigenic culture (TC). Stool samples from 92 patients with suspected CDI were used in this study.
RESULTS: Twenty-five (27.2%) of 92 samples were positive according to the CTA, and 23 (25%) were positive according to the TC. All EIAs and the NAAT test demonstrated sensitivities between 59 and 68% and specificities greater than 91%.
CONCLUSIONS: All four methods exhibited low sensitivities for the diagnosis of CDI, which could lead to a large number of false-negative results, an increased risk of cross-infection to other patients, and overtreatment with empirical antibiotics.
The AmpliVue Clostridium difficile assay and a glutamate dehydrogenase (GDH)-illumigene algorithm were evaluated using 308 diarrheal stool specimens of patients suspected of having C. difficile infection. Compared to the enriched toxigenic culture method, the sensitivities, specificities, and positive and negative predictive values of the AmpliVue C. difficile assay and the GDH-illumigene-based algorithm were 91.7% (95% confidence interval [CI], 76.4 to 97.8), 100% (95% CI, 98.3 to 100), 100% (95% CI, 87 to 100), and 98.9% (95% CI, 96.6 to 99.7), respectively.
We compared the Qiagen artus C. difficile QS-RGQ kit, a new nucleic acid amplification test for the detection of Clostridium difficile toxins in stool specimens, with the Cepheid Xpert C. difficile test. The sensitivity, specificity, positive predictive value, and negative predictive value for the Qiagen artus C. difficile QS-RGQ test were 100%, 89.5%, 60.9%, and 100%, and those for the Cepheid Xpert C. difficile test were 100%, 90%, 62.2%, and 100%, respectively.
