Performance comparison of the cobas Liat and Cepheid GeneXpert systems for Clostridium difficile detection

Abstract

Clostridium difficile infection (CDI) is a high burden and significant cause of healthcare-acquired infectious diarrhea in the United States (US). Timely and accurate diagnosis of CDI enables the rapid initiation of antibiotic therapy and infection control policies to minimize disease transmission. Polymerase chain reaction (PCR) assays have become a preferred modality for diagnosing CDI in the US. The cobas Liat Cdiff PCR test is a novel assay that can be performed on-demand for hospital-based testing with a rapid 20-minute turnaround time from specimen collection to result reporting. We compared the clinical performance of the cobas Liat Cdiff test to the previously introduced Xpert C. difficile/Epi test; both tests are FDA-cleared PCR assays that detect the toxin B (tcdB) gene of C. difficile. Prospectively collected and remnant stool specimens from 310 patients with suspected CDI were obtained for analysis. The cobas Liat Cdiff and Xpert PCR tests showed an overall percent agreement of 97.4% (302/310; 95% CI: 95.0–98.9). Low bacterial burdens of toxigenic C. difficile, indicated by significantly delayed PCR cycle threshold (Ct) values, explained most of the discordance. Positive and negative percent agreement of the cobas Liat Cdiff test compared to the Xpert PCR test were 94.5% (52/55) and 98.0% (250/255), respectively. The clinical performance of the cobas Liat Cdiff test, combined with its simplicity of use and rapid result reporting, provides a reliable option for clinical laboratory use.

Evaluation of the Liat Cdiff Assay for Direct Detection of Clostridioides difficile Toxin Genes within 20 Minutes

“…A prospective comparison between the Liat and Xpert C. difficile/Epi test on fresh samples in the US population found 94.5% and 98.0% positive and negative percent agreement (13). A second prospective study in the U.S. population using the cobas 4800 Cdiff as the reference yielded 95.4% and 99.4% PPA and NPA, respectively (11).…”

An Overview of the Molecular Methods in the Diagnosis of Gastrointestinal Infectious Diseases

“…ese assays are based on integrated systems and do not require the separate nucleic acid extraction step. Several comparative studies with culture and other molecular methods showed these assays to have good correlation and sensitivities and specificities [25][26][27][28]. e remaining three assays, ARIES C. difficile (Luminex, Austin, TX, USA), GeneXpert C. difficile/Epi (Cepheid, Sunnyvale, CA, USA), and Verigene C. difficile (Luminex, Austin, TX, USA), use real-time PCR-based ARIES system, GeneXpert multiplex PCR system, and nanoparticle array hybridization-based Verigene equipment, respectively ( Table 1).…”

“…Several independent studies have been performed on the evaluation of these assays and have sensitivities and specificities in the range of upper 90s [25,26,28]. All of these assays target C. difficile tcdB gene, while GeneXpert C. difficile and Verigene C. difficile assays can also detect hypervirulent ribotype 027 (BI/NAP1/027) strain of C. difficile by targeting the regulatory tcdC gene in which there is a deletion of nucleotide at position number 117 (Δ117tcdC) [25,26,28,29]. Besides, there are several CE-IVD and inhouse assays available for the detection of C. difficile genes ( Table 1).…”