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The Cepheid Xpert® MRSA NxG Control Panel is intended for use as an external assayed positive and negative quality control to monitor the performance of in vitro laboratory nucleic acid testing procedures for the qualitative detection of Methicillin-Resistant Staphylococus aureus performed with the Cepheid Xpert® MRSA NxG Assay on the GeneXpert® Instrument System. The controls comprise cultured and inactivated Methicillin-Resistant Staphylococcus aureus as the positive control and Staphylococcus epidermidis as the negative control.

The Cepheid Xpert® MRSA NxG Control Panel is not intended to replace manufacturer controls provided with the Cepheid Xpert® MRSA NxG Assay.

The Cepheid Xpert® MRSA NxG Control Panel is used to monitor the DNA extraction, amplification and detection processes of the Cepheid Xpert® MRSA NxG Assay. The Cepheid Xpert® MRSA NxG Control Panel contains cultured microorganisms inactivated by heat treatments. Each Cepheid Xpert® MRSA NxG Control Panel consists of 6 individually packaged positive control swabs and 6 individually wrapped negative control swabs. Each positive control swab contains cultured and inactivated Methicillin-Resistant Staphylococcus aureus (MRSA) at arget level that is designed to provide reproducible performance above the limit of detection for each of the genes targeted by the Cepheid Xpert® MRSA NxG Assay: methicillin resistance gene mecA (mec) and the Staphylococcal cassette chromosome (SCC). Each negative contains Staphylococcus epidermidis (MSSE) that is not detected by the Cepheid Xpert® MRSA NxG Assay. Each swab is individually wrapped with a desiccant in a heat-sealed foil pouch.

Here's a breakdown of the acceptance criteria and study details for the Cepheid Xpert® MRSA NxG Control Panel, based on the provided text:

Acceptance Criteria and Reported Device Performance

(Note: The provided text doesn't explicitly state the acceptance criteria as separate from the performance, but the 100% agreement achieved suggests this was the expected outcome for a control panel's precision and reproducibility study.)

Study Details

1. Sample size used for the test set and the data provenance:

   • Sample Size:
     • For Positive Controls: 93 tests (32 at Site 1, 31 at Site 2, 30 at Site 3).
     • For Negative Controls: 92 tests (31 at Site 1, 31 at Site 2, 30 at Site 3).
   • Data Provenance: The study was conducted at three different testing locations (referred to as Site 1, Site 2, and Site 3). The document does not specify the country of origin, but it implies a prospective study since it describes "a precision and reproducibility study was conducted."

2. Number of experts used to establish the ground truth for the test set and the qualifications of those experts:

   • The concept of "ground truth" as established by experts (e.g., radiologists) is not applicable here. This is a study for a quality control material for a diagnostic assay, not an AI diagnostic device evaluating patient data. The "ground truth" for the control material is inherently defined by its composition (e.g., inactivated Methicillin-Resistant Staphylococcus aureus for the positive control, Staphylococcus epidermidis for the negative control) and the known expected results from the Cepheid Xpert® MRSA NxG Assay.

3. Adjudication method for the test set:

   • Not applicable. As this is a study for a quality control material, the results are objective (positive/negative detection) based on the performance of the assay with the control. There's no subjective interpretation requiring adjudication among experts. The study reports raw agreement percentages. Any "ERROR" responses were retested with a new control, indicating a procedural re-evaluation rather than expert adjudication of a result.

4. 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:

   • No. This type of study (MRMC for AI) is not applicable to a quality control panel. This product is a control material for an in-vitro diagnostic assay, not an AI-powered diagnostic device.

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

   • Yes, in essence. The "device performance" refers to the performance of the control panel itself, which is then used by human operators with the GeneXpert® Instrument System and Cepheid Xpert® MRSA NxG Assay. While human operators are involved in running the test, the evaluation of the control material's performance against the assay's expected results is a standalone assessment of the control material's ability to consistently produce those results. This isn't an AI algorithm; rather, it's a quality control for an existing diagnostic system.

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

   • The "ground truth" for the control panel is based on its known composition and the expected analytical performance when run on the target assay. For the positive control, the ground truth is the presence of Methicillin-Resistant Staphylococcus aureus (mec, SCC) at a level detectable by the assay. For the negative control, the ground truth is the presence of Staphylococcus epidermidis which should not be detected by the target assay.

7. The sample size for the training set:

   • Not applicable. This study is for a quality control material, not a machine learning or AI algorithm that requires a training set. The "samples" used are the control materials themselves tested on the assay system.

8. How the ground truth for the training set was established:

   • Not applicable. As there is no training set for an AI algorithm, this question is not relevant to the described device and study.

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