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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 aztreonam at concentrations of 0.5-64 µg/mL to the test panel. Testing is indicated for Enterobacterales and Pseudomonas aeruginosa, as recognized by the FDA Susceptibility Test Interpretive Criteria (STIC) webpage.

The MicroScan Dried Gram-Negative MIC/Combo Panels with Aztreonam (AZT) (0.5-64 µg/mL) has demonstrated acceptable performance with the following organisms:

Enterobacterales (Citrobacter freundii complex, Citrobacter koseri, Escherichia coli, Klebsiella oxytoca, Klebsiella pneumoniae, Proteus mirabilis, Morganella morganii, Yersinia enterocolitica)

Pseudomonas aeruginosa

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.

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

The provided FDA 510(k) clearance letter pertains to an Antimicrobial Susceptibility Test (AST) system, specifically the MicroScan Dried Gram-Negative MIC/Combo Panels with Aztreonam. It is not an AI/ML medical device. Therefore, many of the requested criteria regarding AI-specific study design (like MRMC studies, number of experts for AI ground truth, training set details) are not applicable to this type of device and study.

However, I can extract the relevant acceptance criteria and performance data for this AST device based on the provided document.

Acceptance Criteria and Device Performance (for an AST System)

The study proves the device's performance through comparison with a CLSI (Clinical and Laboratory Standards Institute) frozen Reference Panel. The criteria primarily revolve around "Essential Agreement (EA)" and "Categorical Agreement (CA)" between the new device and the reference method.

1. Table of Acceptance Criteria and Reported Device Performance

Note: The document implicitly refers to the "Class II Special Controls Guidance Document: Antimicrobial Susceptibility Test (AST) Systems; Guidance for Industry and FDA", dated August 28, 2009. This guidance typically defines the statistical acceptance criteria for EA and CA for AST systems. The document states the device "demonstrated substantially equivalent performance when compared with a CLSI frozen Reference Panel, as defined in the FDA document..." meeting "acceptable performance."

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

• The document mentions "external evaluations were conducted with contemporary and stock Efficacy isolates and stock Challenge strains."
• Specific numerical sample sizes for the test set (number of isolates/strains) are not explicitly stated in the provided text.
• Data Provenance: The document does not specify the country of origin. It indicates the use of "contemporary and stock Efficacy isolates and stock Challenge strains," which suggests a mix of clinical and laboratory strains. The study appears to be prospective in nature, as new data was generated for this specific submission to demonstrate performance against a reference standard.

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

• This is an AST system, not an AI/ML device requiring expert radiological annotation.
• Ground Truth Establishment: The ground truth (reference MIC values and categorical interpretations) for the test set was established by a CLSI frozen Reference panel. This is a recognized standard method for AST device validation. The "experts" in this context are the established CLSI methodologies and laboratories that produce these reference panels, not individual human readers or annotators in the typical AI/ML sense.

4. Adjudication Method for the Test Set

• Adjudication, as typically described (e.g., 2+1, 3+1), is not applicable here because the ground truth is established by a standardized laboratory method (CLSI frozen Reference panel), not by consensus among human experts annotating medical images. The comparison is objective, based on measured MIC values.

5. If a Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study Was Done

• No, an MRMC comparative effectiveness study was not done. This type of study is specific to diagnostic imaging devices where human readers interpret medical images with and without AI assistance.
• This device is an in vitro diagnostic (IVD) antimicrobial susceptibility test system, where the output is a MIC value and a categorical interpretation for a bacterial isolate, not an image interpretation by a human observer.

6. If a Standalone (Algorithm Only Without Human-in-the Loop Performance) Was Done

• This question is framed for AI/ML algorithms. While the device automation ("MicroScan instrumentation," "WalkAway instrument") is a component, the "standalone performance" here refers to the device's ability to accurately determine MIC and categorize susceptibility when compared to the CLSI reference method.
• The study did evaluate the device's performance independently of human interpretation, as it explicitly states panels can be "read either visually or with MicroScan instrumentation." The reported EA and CA numbers reflect the system's performance, including automated reading where applicable.

7. The Type of Ground Truth Used

• Reference Standard: The ground truth used was a CLSI frozen Reference Panel. This is considered the gold standard for comparing the performance of new antimicrobial susceptibility test devices. It provides "true" Minimum Inhibitory Concentration (MIC) values for the bacterial isolates against the antimicrobial agent.

8. The Sample Size for the Training Set

• This is an IVD device, not an AI/ML system that undergoes a separate "training" phase with a large dataset in the sense of machine learning. The device's underlying "knowledge" is built into its design, chemistry, and reading algorithms (for automated methods).
• Therefore, the concept of a "training set" as understood in AI/ML is not applicable to this device.

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

• As the concept of a "training set" as in AI/ML does not apply here, this point is not applicable. The device's development involved standard microbiological and analytical chemistry principles, validated against established reference methods.

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