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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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