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The MicroScan® Dried Gram-Positive MIC/Combo Panel is used to determine quantitative and/or qualitative antimicrobial agent susceptibility of colonies grown on solid media of rapidly growing aerobic and facultative anaerobic gram-positive cocci. After inoculation, panels are incubated for 16-20 hours at 35°C +/- 1°C in a non-CO2 incubator, and read either visually or with MicroScan instrumentation, according to the Package Insert.

This submission is to evaluate the performance of the antimicrobial agent Erythromycin on the MicroScan® Dried Gram-Positive MIC/Combo Panels read on MicroScan® WalkAway and autoSCAN-4 Instruments utilizing the current DMS or LabPro version

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The provided text describes the 510(k) premarket notification for the MicroScan® Dried Gram-Positive MIC/Combo Panels with Erythromycin. This document is focused on the regulatory approval rather than a detailed study report with all the specific elements requested for acceptance criteria and study design.

However, based on the information provided, we can infer some details and highlight what is explicitly stated:

1. Table of Acceptance Criteria and Reported Device Performance & 7. Type of Ground Truth Used:

The document mentions that the submission is "to evaluate the performance of the antimicrobial agent Erythromycin." In the context of antimicrobial susceptibility testing (AST) devices, the primary acceptance criteria typically revolve around the agreement between the new device's readings and a reference method (the "ground truth"). This agreement is often measured in terms of Essential Agreement (EA) and Category Agreement (CA). For AST devices, the ground truth is usually established by a recognized reference method, such as broth microdilution or agar dilution, often performed manually.

While the specific numerical acceptance criteria (e.g., "≥90% EA") and the reported performance (e.g., "95% EA") are not explicitly stated in this regulatory letter, they would have been part of the underlying study submitted to the FDA.

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

• Test Set Organism: The document explicitly states that the organisms used for Erythromycin susceptibility testing in this panel are: Staphylococcus aureus.
• Sample Size: The exact number of Staphylococcus aureus isolates used for the test set is not specified in the provided text.
• Data Provenance: The provenance (e.g., country of origin, retrospective or prospective) of the data is not specified in the provided text.

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

• This information is not specified in the provided text. For AST devices, the "experts" are typically the trained microbiologists or laboratory personnel who perform and interpret the reference method.

4. Adjudication method for the test set:

• This information is not specified in the provided text. For AST, adjudication is less about expert consensus on image interpretation and more about resolving discrepancies between the device and the reference method, possibly through re-testing or using an alternative 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:

• This is not applicable to this device. This is an antimicrobial susceptibility testing device, read either visually or with instrumentation. There is no AI component or human-in-the-loop "reading" in the sense of medical imaging interpretation that would warrant an MRMC study comparing human readers with and without AI assistance. The "readers" here are either the instruments (MicroScan® WalkAway and autoSCAN-4) or a human visually interpreting the panel.

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

• Yes, this is effectively a standalone performance evaluation. The device (MicroScan® Dried Gram-Positive MIC/Combo Panels) in conjunction with the MicroScan® WalkAway and autoSCAN-4 Instruments and associated software (DMS or LabPro version

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The MicroScan® Dried Gram-Positive MIC/Combo Panel is used to determine quantitative and/or qualitative antimicrobial agent susceptibility of colonies grown on solid media of rapidly growing aerobic and facultative anaerobic gram-positive cocci. Panels are incubated for 16 – 20 hours at 35℃ +/- 1℃ in a non-CO2 incubator, and read either visually or with MicroScan instrumentation, according to the Package Insert.

This particular submission is for the addition of the antimicrobial Erythromycin at concentrations of 0.25 to 16 mcg/ml to the test panel.

The gram-positive organisms which may be used for Erythromycin susceptibility testing in this panel are:

Staphylococcus aureus

MicroScan® Dried Gram-Positive MIC/Combo Panels are designed for use in determining quantitative and/or qualitative antimicrobial agent susceptibility of colonies grown on solid media of rapidly growing aerobic and facultative anaerobic gram-positive cocci.

The antimicrobial susceptibility tests are miniaturizations of the broth dilution susceptibility test that have been diluted in broth and dehydrated. Various antimicrobial agents are diluted in broth to concentrations bridging the range of clinical interest. Panels are rehydrated with water after inoculation with a standardized suspension of the organism. After incubation in a non-CO2 incubator for 16-20 hours, the minimum inhibitory concentration (MC) for the test organism is read by determining the lowest antimicrobial concentration showing inhibition of growth.

Here's a breakdown of the acceptance criteria and study information for the MicroScan® Dried Gram-Positive MIC/Combo Panels with Erythromycin, based on the provided text:

1. Acceptance Criteria and Reported Device Performance

2. Sample Size and Data Provenance

• Test Set:
  • Sample Size: Not explicitly stated in the provided text. The evaluation was conducted with "fresh and stock Efficacy isolates and stock Challenge strains." The exact number of isolates/strains used is not provided.
  • Data Provenance: Not explicitly stated. Given it's an "external evaluation" conducted in support of an FDA submission, it's likely multi-center data, but the specific countries of origin are not mentioned. The study was prospective in the sense that it was designed to confirm the acceptability of the proposed panel.

3. Number of Experts and Qualifications for Ground Truth (Test Set)

• Number of Experts: Not explicitly stated.
• Qualifications of Experts: Not explicitly stated. However, the ground truth was established by an "NCCLS frozen Reference Panel," which implies adherence to standards and expert-derived values, but no specific personnel details are given. The "Expected Results" for Challenge strains would also be based on established expert knowledge or prior testing.

4. Adjudication Method (Test Set)

• Adjudication Method: Not explicitly stated. The comparison was primarily against an "NCCLS frozen Reference Panel" and "Expected Results" for challenge strains, serving as the benchmark. This suggests a direct comparison rather than a human adjudication process between different readers of the device.

5. Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study

• Was an MRMC study done? No. This device is an automated in vitro diagnostic (IVD) test for antimicrobial susceptibility. The assessment is against a reference method and established quality control, not against human readers evaluating medical images or similar.

6. Standalone Performance Study

• Was a standalone study done? Yes. The study directly assessed the performance of the MicroScan® Dried Gram-Positive MIC/Combo Panels with Erythromycin (the algorithm/device) against the NCCLS frozen Reference Panel. The reported "Essential Agreement of >96% for Erythromycin" is a measure of its standalone performance compared to the gold standard. Reproducibility and Quality Control testing also evaluate the device's intrinsic performance.

7. Type of Ground Truth Used

• The ground truth used was:
  • Reference Method Comparison: An "NCCLS frozen Reference Panel." This is a standardized, recognized method for determining antimicrobial susceptibility, considered the gold standard for comparison in these types of studies.
  • Expected Results: For "stock Challenge strains," the panels were compared to "Expected Results determined prior to the evaluation." These expected results would be derived from pre-established, verified susceptibility profiles for those specific strains.

8. Sample Size for the Training Set

• Sample Size: Not applicable. This summary describes the validation of a physical diagnostic panel (Microdilution MIC panel), not a machine learning algorithm that requires a "training set" in the conventional sense. The "training" for such a device involves formulation, manufacturing, and internal QC processes to ensure consistency and accuracy, rather than data-driven model training.

9. How Ground Truth for the Training Set Was Established

• How Ground Truth Was Established: Not applicable, as there is no "training set" in the context of a machine learning algorithm. The panel's design and manufacturing are based on established microbiological principles for antimicrobial susceptibility testing, with the concentrations of antimicrobial agents diluted in broth to "concentrations bridging the range of clinical interest." The performance of the resulting panel is then validated against reference standards.

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