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The MicroScan MICroSTREP plus® Panel is used to determine quantitative and/or qualitative antimicrobial agent susceptibility of colonies grown on solid media of aerobic streptococci, including Streptococcus pneumoniae. After inoculation, panels are incubated for 20 ~ 24 hours at 35°C +/- 1°C in a non-CO2 incubator, and read visually according to the Package Insert. Additionally, the panels may be incubated in and read by a MicroScan® WalkAway instrument.

To determine bacterial antimicrobial agent susceptibility

This particular submission is for the addition of instrument read capability of the antimicrobial Penicillin, at concentrations of 0.015 to 16 mcg/ml on the MicroScan MICroSTREP plus® Panel.

The MicroScan MICroSTREP plus® Panel is used to determine quantitative and/or qualitative antimicrobial agent susceptibility of colonies grown on solid media of aerobic streptococci, including Streptococcus pneumoniae. After inoculation, panels are incubated for 20 – 24 hours at 35°C +/- 1°C in a non-CO2 incubator, and read according to the Package Insert. Additionally, the panels may be incubated in and read by a MicroScan® WalkAway instrument.

The antimicrobial susceptibility tests are miniaturizations of the broth dilution susceptibility test. The antimicrobial agents are diluted in water, buffer or minute concentrations of broth to various concentrations. Panels are rehydrated with 115 ul Mueller Hinton Broth with 2-5% lysed horse blood (LHB) and buffered with 50 mM HEPES, after inoculation of the broth with a standardized suspension of the organism in saline. After incubation in a non-CO2 incubator for 20-24 hours, the minimum inhibitory concentration (MIC) for the organism is read by observing the lowest antimicrobial concentration that inhibits visible growth.

Here's a breakdown of the acceptance criteria and the study that proves the device meets them, based on the provided text:

Acceptance Criteria and Device Performance

Note: The FDA guidance document mentioned for Essential Agreement (February 5, 2003) would contain the specific numerical thresholds for "acceptable performance." Without access to that document, the exact numerical threshold can't be filled in, but the device explicitly states it met this criteria.

Study Details

2. Sample Size Used for the Test Set and Data Provenance

• Sample Size for Test Set: The document mentions "stock and CDC Challenge strains" were used for the external evaluation. However, the exact number of strains or individual isolates tested is not specified in the provided text.
• Data Provenance: The study was an "external evaluation" conducted with "stock and CDC Challenge strains." This suggests a controlled laboratory setting, likely with well-characterized strains from established repositories like the CDC. It is a prospective evaluation designed to assess the new instrument's performance against established methods. The country of origin for the data is not explicitly stated, but given the FDA submission and CDC strains, it's highly likely to be the United States.

3. Number of Experts Used to Establish the Ground Truth for the Test Set and Qualifications

• Number of Experts: Not specified.
• Qualifications of Experts: Not specified.
  The "Expected Results" were determined by the company's MicroScan MICroSTREP plus® Panel. This implies that the standard, predicate method (read visually or by a human) was used to establish the ground truth. While experts would be involved in interpreting those results, the specific number and qualifications are not detailed.

4. Adjudication Method for the Test Set

• Adjudication Method: The ground truth was established by "Expected Results determined [from] the MicroScan MICroSTREP plus® Panel" (likely the predicate device's standard method). This suggests a comparative method rather than typical expert adjudication. The text does not describe a specific adjudication method like 2+1 or 3+1. It's an "external evaluation" where the instrument's performance is compared against these predetermined "Expected Results."

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

• MRMC Study: No, a multi-reader multi-case comparative effectiveness study was not explicitly described in the provided text. The study focused on the performance of the instrument-read method compared to "Expected Results" from the predicate device, not on comparing human readers with and without AI assistance.
• Effect Size of Human Improvement: Therefore, no effect size for human readers with and without AI assistance is provided.

6. Standalone (Algorithm Only) Performance

• Standalone Performance: Yes, a standalone performance evaluation was conducted. The entire study describes the performance of the "proposed instrument read method" (the MicroScan® WalkAway instrument reading the panels) for Penicillin, without explicit human intervention in the reading process that is being evaluated. The device itself is the "algorithm only" component being assessed for reading the MIC panels.

7. Type of Ground Truth Used

• Type of Ground Truth: The ground truth used was established by the "Expected Results determined [from] the MicroScan MICroSTREP plus® Panel." This refers to the results obtained from the predicate method (which can be read visually or by a WalkAway instrument, but for the purpose of establishing ground truth for the new instrument-read claim, it would be the established/validated method). This is a form of expert consensus/established method comparison, where the predicate device's validated results serve as the reference standard.

8. Sample Size for the Training Set

• Sample Size for Training Set: The document does not provide any information about a training set or its sample size. This type of device (an automated reader for MIC panels) is typically validated through comparison to known reference methods with a test set, rather than "training" in the machine learning sense.

9. How the Ground Truth for the Training Set Was Established

• Ground Truth for Training Set: Since no training set is mentioned, information on how its ground truth was established is not applicable.

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