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The cobas® Cdiff Nucleic acid test for use on the cobas® Liat® System is an automated, qualitative in vitro diagnostic test, that uses real-time polymerase chain reaction (PCR), for the detection of the toxin B (tcdB) gene of toxigenic Clostridioides difficile (C.difficile) in unformed (liquid or soft) stool specimens obtained from patients suspected of having C. difficile Infection (CDI). The cobas® Cdiff Nucleic acid test for use on the cobas® Liat® System is intended for use as an aid in the diagnosis of CDI in humans in conjunction with clinical and epidemiological risk factors.

The cobas® Cdiff Nucleic Acid Test for use on the cobas® Liat® System (cobas® Cdiff) is a rapid, automated in vitro diagnostic test for qualitative detection and differentiation of C. difficile DNA in human stool specimens. The cobas® Liat® is for in vitro diagnostic use. The system is designed to identify and/or measure presence of genetic material in a biological sample. The system automates all nucleic acid amplification test (NAAT) processes, including reagent preparation, target enrichment, inhibitor removal, nucleic acid extraction, amplification, real-time detection, and result interpretation in a rapid manner. The cobas® Cdiff test uses silica magnetic particle-based nucleic acid extraction and TaqMan probe-based real-time PCR amplification and detection. The cobas® Liat® Analyzer automates and integrates sample purification, nucleic acid amplification and detection of the target sequence in biological samples. Other than adding the sample to the cobas® Cdiff assay tube, no reagent preparation or additional steps are required. The cobas® Cdiff assay tube that holds all of the sample purification and PCR reagents and hosts the sample preparation and PCR process specific for the Cdiff analyte. The test uses the assay tube as both the sample and reaction vessel. The assay tube comprises flexible tubing containing all required unit dose reagents pre-packed in tube segments, separated by pressure-sensitive seals, in the order of reagent use. During the testing process, multiple sample processing actuators of the analyzer compress the cobas® Cdiff assay tube to selectively release reagents from tube segments, move the sample from one segment to another, and control reaction conditions such as reaction volume, temperature, pressure, and incubation time. Precise control of all these parameters provides optimal conditions for assay reactions, allowing the test to achieve high performance similar to or better than that of currently available molecular assays. The cobas® Liat® Analyzer software controls and coordinated these actions to perform all required assay processes, including sample preparation, nucleic acid extraction, target enrichment, inhibitor removal, nucleic acid elution, and real-time PCR. All assay steps are performed within the closed and self-contained cobas® Cdiff assay tube, thereby eliminating the potential for cross-contamination between samples. The collected data are automatically analyzed and the result is displayed in the assay report on the integrated LCD touch screen of the cobas® Liat® Analyzer.

The document provided does not contain the level of detail required to answer all aspects of your request. Specifically, it is a 510(k) summary for a change in shelf life for an existing device, the cobas® Cdiff Nucleic Acid Test. Therefore, it focuses on demonstrating that this change does not negatively impact performance, rather than providing all the original study details for the device's initial clearance.

Here's an analysis of the provided text in relation to your questions:

1. A table of acceptance criteria and the reported device performance.

The document does not explicitly state specific numerical acceptance criteria for the initial device performance. It focuses on demonstrating that the performance of the device with the new shelf life is equivalent to the currently cleared device.

However, it does mention a new stability study was performed with "modified stability testing approach and acceptance criteria." It then states the result:

2. Sample size used for the test set and the data provenance (e.g., country of origin of the data, retrospective or prospective).

The document mentions a "new stability study" was performed to verify the shelf life. It does not provide:

• Sample size: No explicit number of samples or runs for this stability study is provided.
• Data Provenance: Not mentioned (e.g., country of origin).
• Retrospective/Prospective: Implied to be prospective for the shelf-life stability study, as it's a "new stability study." However, for the original clearance of the device itself, this information is not provided.

3. Number of experts used to establish the ground truth for the test set and the qualifications of those experts (e.g., radiologist with 10 years of experience).

This device is an in vitro diagnostic (IVD) test for detecting a bacterial gene (Clostridioides difficile toxin B gene). The "ground truth" for such a test would typically be established by:

• Reference methods: E.g., bacterial culture, toxigenic culture, or a highly sensitive and specific laboratory reference PCR assay.
• Clinical diagnosis: Based on patient symptoms, other lab tests, and clinical assessment.

This document does not mention the use of human experts (like radiologists) for ground truth establishment. For an IVD, the "experts" are the laboratory and clinical staff following established protocols to provide the comparator data. The document does not specify details about these "experts" or their qualifications.

4. Adjudication method (e.g., 2+1, 3+1, none) for the test set.

Not applicable or not mentioned. Adjudication methods like 2+1 or 3+1 are typically used in image analysis studies where human readers interpret images. For an IVD, the comparison is usually against a pre-defined "gold standard" or reference method.

5. If a multi-reader multi-case (MRMC) comparative effectiveness study was done, If so, what was the effect size of how much human readers improve with AI vs without AI assistance.

Not applicable. This is an IVD test, not an AI-powered diagnostic imaging device that assists human readers.

6. If a standalone (i.e. algorithm only without human-in-the-loop performance) was done.

Yes, by its nature, an IVD test like the cobas® Cdiff Nucleic Acid Test on the cobas® Liat® System is a standalone device. The "algorithm" here refers to the pre-programmed steps of nucleic acid extraction, amplification, and real-time detection performed by the automated system, leading to a qualitative result (positive/negative). The document states: "The cobas® Liat® Analyzer automates and integrates sample purification, nucleic acid amplification and detection of the target sequence in biological samples... The collected data are automatically analyzed and the result is displayed in the assay report on the integrated LCD touch screen of the cobas® Liat® Analyzer." This indicates standalone performance.

7. The type of ground truth used (expert consensus, pathology, outcomes data, etc).

The document implies the ground truth for establishing initial performance would have been comparison to a reference method, likely a combination of toxigenic C. difficile culture and a highly reliable molecular method, or clinical diagnosis supported by confirmatory lab tests in the original clearance (K171770). For the current shelf-life stability study, the ground truth appears to be the expectation that the device continues to perform according to its established analytical specifications when tested at different time points after manufacturing. It refers to "assay performance and claims."

8. The sample size for the training set.

Not applicable/Not mentioned. As an IVD test, there isn't a "training set" in the machine learning sense. The device's performance is established through analytical and clinical validation studies with defined sample sizes. The document doesn't provide these sizes for the original device, nor for any "training" in the context of this specific 510(k) which is for a shelf-life change.

9. How the ground truth for the training set was established.

Not applicable/Not mentioned for the same reasons as #8. For an IVD, the "ground truth" for validation studies (analogous to a test set in ML) would be established by reference methods or clinical diagnosis.

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