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To determine bacterial antimicrobial agent susceptibility. 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 degrees C +/- 1 degree 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. This particular submission is for the addition of instrument read capability of the antimicrobial Tetracycline, at concentrations of 0.06 to 16 mcg/ml on the MicroScan MICroSTREP plus Panel. The organisms which may be used for Tetracycline susceptibility testing on this panel are: Streptococcus spp., Streptococcus pneumoniae.

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 degrees C +/- 1 degree 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 varying concentrations in the wells of the panels. 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 test organism is usually read by observing the lowest antimicrobial concentration that inhibits visible growth of the test organism. Panels may be incubated in and read by a MicroScan WalkAway instrument.

Here's an analysis of the provided text regarding the acceptance criteria and study for the MicroScan MICroSTREP plus® Panel with Tetracycline:

Acceptance Criteria and Device Performance

Note: The FDA guidance document likely specifies numerical thresholds for "Essential Agreement" and criteria for "acceptable reproducibility" and "acceptable Quality Control results." These specific numerical acceptance thresholds are not provided in the summary. The summary only states that the device met these acceptable criteria.

Study Information

Here's a breakdown of the study details based on the provided text:

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

   • Test Set Sample Size: Not explicitly stated as a single number. The study utilized "stock and CDC Challenge strains." The text notes that the "proposed instrument read method for the MicroScan MICroSTREP plus® Panel demonstrated substantial equivalence with streptococcal isolates when compared with an expected Substantially Equivalent result generated on a CLSI frozen Reference Panel." While the types of strains are mentioned, the exact number of isolates used in the external evaluation for performance assessment is not provided.
   • Data Provenance: Not explicitly stated (e.g., country of origin). The use of "CDC Challenge strains" suggests some US-based origin, but this isn't definitive for the entire "stock" collection. The study was an "external evaluation." It is implicitly prospective in the sense that new data was generated for this specific submission, comparing instrument reads to expected results.

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

   • The text does not specify the number of experts or their qualifications for establishing the "Expected Result" (ground truth). It refers to the "CLSI frozen Reference Panel" as the basis for the "Expected Result," implying that CLSI (Clinical and Laboratory Standards Institute) standards and potentially expert consensus or established methodologies were used to define these reference results.

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

   • Not specified. The "Expected Result" is associated with the "CLSI frozen Reference Panel," implying a standardized, reference-based determination rather than a multi-reader visual adjudication process.

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, a multi-reader multi-case (MRMC) comparative effectiveness study was not explicitly described. This study focuses on validating an instrument read method compared to an "Expected Result" based on a reference standard, not on human reader performance or improvement with AI assistance. The "instrument read method" is an automated reading by the MicroScan® WalkAway instrument, replacing or supplementing visual reading, rather than an AI-assisted human reading. The summary states panels "may be incubated in and read by a MicroScan® WalkAway instrument" in addition to visual reading, indicating it's an alternative or supplemental method, but not explicitly an AI-assisted human reading.

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

   • Yes, this was a standalone performance evaluation of the "instrument read method" (referred to as the "proposed instrument read method" and instrument read results). The MicroScan® WalkAway instrument's reading is essentially an algorithm-only or automated standalone performance, independent of a human directly interpreting results for the performance metric of "Essential Agreement."

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

   • The ground truth was established by "Expected Results determined [from] the CLSI frozen Reference Panel." This suggests a reference standard method (broth dilution susceptibility test, as described in the summary) and likely expert-developed CLSI guidelines. It's akin to a "gold standard" derived from established laboratory protocols and reference materials.

7. The sample size for the training set:

   • Not applicable/Not provided. The text describes an evaluation or validation study for a device, not the development or training of a machine learning model. Therefore, a "training set" in the context of AI/ML is not relevant here. The device determines MIC values based on a pre-programmed methodology, not learned from a dataset.

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

   • Not applicable (as it's not an AI/ML model with a training set).

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