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The MicroScan Dried Gram-Negative MIC/Combo Panel is used to determine quantitative and qualitative antimicrobial agent susceptibility of colonies grown on solid media of rapidly growing aerobic and facultative anaerobic gram-negative bacilli. 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 particular submission is for the addition of the antimicrobial cefepime at concentrations of 0.12-64 µg/mL to the test panel. Testing is indicated for Enterobacterales, Pseudomonas aeruginosa and Aeromonas spp., as recognized by the FDA Susceptibility Test Interpretive Criteria (STIC) webpage.

The MicroScan Dried Gram-Negative MIC/Combo Panels with Cefepime (CPE) (0.12-64µg/mL) has demonstrated acceptable performance with the following organisms:

Enterobacterales (Enterobacter spp., Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis, Citrobacter koseri, (formerly Citrobacter diversus), Citrobacter freundii complex (Citrobacter freudnii, Citrobacter werkmanii and Citrobacter youngae), Klebsiella oxytoca, Morganella morganii, Proteus vulgaris, Providencia stuartii, Providencia rettgeri, Serratia marcescens)

Pseudomonas aeruginosa

Aeromonas spp.

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

The principle of MicroScan panels with 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 (MIC) for the test organism is read by determining the lowest antimicrobial concentration showing inhibition of growth.

The product is single-use and intended for laboratory professional use.

Device Performance Acceptance Criteria and Study Details for MicroScan Dried Gram-Negative MIC/Combo Panels with Cefepime

Based on the provided FDA 510(k) Clearance Letter, the device in question is the MicroScan Dried Gram-Negative MIC/Combo Panels with Cefepime (CPE) (0.12-64 µg/mL), which is an Antimicrobial Susceptibility Test (AST) System. The study described focuses on demonstrating the substantial equivalence of this new configuration (with Cefepime) to a predicate device.

Given the nature of the device (an AST System), the "acceptance criteria" are typically related to the accuracy of determining Minimum Inhibitory Concentration (MIC) and the resulting categorical agreement (Susceptible, Intermediate, Resistant) compared to a reference method. The "study that proves the device meets the acceptance criteria" refers to the performance evaluation conducted for the 510(k) submission.

1. Table of Acceptance Criteria and Reported Device Performance

For AST systems, the key performance metrics are Essential Agreement (EA) and Categorical Agreement (CA) when compared to a CLSI (Clinical and Laboratory Standards Institute) frozen reference panel. The FDA document "Class II Special Controls Guidance Document: Antimicrobial Susceptibility Test (AST) Systems; Guidance for Industry and FDA", dated August 28, 2009, likely outlines the specific acceptance criteria thresholds for EA and CA. While the exact numerical acceptance criteria are not explicitly stated in the provided text, the performance "demonstrated acceptable performance" implies meeting these pre-defined thresholds.

Important Note: The document highlights some instances where the performance was "outside of essential agreement" for Enterobacterales with Prompt inoculation and "below 90%" for Aeromonas spp. with turbidity inoculation and WalkAway read method. These discrepancies are "mitigated with a limitation" in the product labeling, suggesting that while initial performance in those specific conditions did not meet implicit criteria, the overall robust performance with other methods/organisms, coupled with labeling limitations, made the device acceptable for clearance.

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

• Sample Size: The document does not explicitly provide a total number for the test set sample size (e.g., number of isolates tested). It refers to "contemporary and stock Efficacy isolates and stock Challenge strains" used for external evaluations.
• Data Provenance: The document does not specify the country of origin of the data. It mentions "external evaluations," which generally implies testing conducted at clinical sites or contract research organizations. The study appears to be retrospective in the sense that it uses "stock Efficacy isolates and stock Challenge strains" which are pre-existing collections of bacterial isolates. It also mentions "contemporary" isolates, suggesting some recent collection. It implies a laboratory-based performance study rather than a clinical trial with patient outcomes.

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

This type of device (AST System) does not typically rely on human expert interpretation for establishing the "ground truth" of the test set. The ground truth for antimicrobial susceptibility testing is established by a reference method, which for this device is stated as a "CLSI frozen Reference Panel."

Therefore:

• Number of Experts: Not applicable in the context of creating the ground truth for AST.
• Qualifications of Experts: Not applicable.

4. Adjudication Method for the Test Set

As the ground truth is established by a reference method (CLSI frozen Reference Panel), there is no human adjudication method like 2+1 or 3+1 typically used for image-based diagnostics. The device's results are directly compared to the quantitatively or qualitatively determined results from the CLSI 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

There is no indication that an MRMC comparative effectiveness study was performed. This type of study is not relevant for this device, which is an automated or manually read laboratory diagnostic for antimicrobial susceptibility, not an AI-assisted diagnostic tool that aids human readers in interpretation. The device itself performs the susceptibility test.

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

Yes, the performance data presented is effectively standalone performance of the device (MicroScan Dried Gram-Negative MIC/Combo Panels with Cefepime). The device "read either visually or with MicroScan instrumentation" and its performance (Essential Agreement, Categorical Agreement) is directly compared to the reference standard. The "human-in-the-loop" would be the laboratory professional reading the results, and the study evaluates the accuracy of the device itself in producing those results. Where visual reads are mentioned, it's about the device's ability to produce clear inhibition patterns for visual interpretation, not a human independently interpreting raw data without the device.

7. The Type of Ground Truth Used

The ground truth used was established by a CLSI frozen Reference Panel. This is a recognized and standardized method for determining antimicrobial susceptibility, often involving broth microdilution or agar dilution methods where organisms are tested against known concentrations of antimicrobials. It is a highly controlled and quantitative method to determine the true MIC value against which the device's performance is compared.

8. The Sample Size for the Training Set

The document does not mention a training set or any details about its sample size. This is consistent with the nature of the device. AST systems are generally rule-based or empirically derived systems based on established microbiological principles, rather than machine learning models that require distinct training sets. The development of such panels involves extensive empirical testing during the R&D phase to ensure the correct concentrations and formulations, but this isn't typically referred to as a "training set" in the context of an AI/ML model.

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

As no training set (in the AI/ML sense) is indicated, this point is not applicable.

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