(210 days)
VITEK® 2 AST-Gram Negative Cefazolin is designed for antimicrobial susceptibility testing of Gram negative bacilli and is intended for use with the VITEK® 2 and VITEK® 2 Compact Systems as a laboratory aid in the determination of in vitro susceptibility to antimicrobial agents. VITEK® 2 AST-Gram Negative Cefazolin is a quantitative test. Cefazolin has been shown to be active against most strains of the microorganisms listed below, according to the FDA label for this antimicrobial.
Active in vitro and in clinical infections: Escherichia coli Proteus mirabilis
The VITEK® 2 Gram-Negative Susceptibility Card is intended for use with the VITEK® 2 Systems in clinical laboratories as an in vitro test to determine the susceptibility of clinically significant aerobic Gram-negative bacilli to antimicrobial agents when used as instructed.
The principle of the VITEK® 2 AST cards is based on the microdilution minimum inhibitory concentration (MIC) technique reported by MacLowry and Marsh() and Gerlach(0). The VITEK® 2 AST card is essentially a miniaturized, abbreviated and automated version of the doubling dilution technique(3).
Each VITEK® 2 AST card contains 64 wells. A control well which only contains microbiological culture media is resident on all cards. The remaining wells contain premeasured portions of a specific antibiotic combined with culture media. The bacterial or yeast isolate to be tested is diluted to a standardized concentration with 0.45 - 0.5% saline before being used to rehydrate the antimicrobial medium within the card. The VITEK® 2 System automatically fills, seals and places the card into the incubator/reader. The VITEK® 2 Compact has a manual filling, sealing and loading operation. The VITEK® 2 Systems monitor the growth of each well in the card over a defined period of time. At the completion of the incubation cycle, a report is generated that contains the MIC value along with the interpretive category result for each antibiotic contained on the card.
VITEK® 2 AST-GN Cefazolin (≤1 - ≥32 µg/mL) has the following concentrations in the card: 1, 2, and 8 ug/mL (equivalent standard method concentration by efficacy in ug/mL).
The provided text describes the performance study for the VITEK® 2 AST-Gram Negative Cefazolin (≤1 - ≥32 µg/mL) device, which is an antimicrobial susceptibility testing system.
Here's a breakdown of the requested information:
1. Table of Acceptance Criteria and Reported Device Performance:
The acceptance criteria for AST systems are defined in the FDA Class II Special Controls Guidance Document: Antimicrobial Susceptibility Test (AST) Systems; Guidance for Industry and FDA (Issued August 28, 2009). While the specific numerical thresholds for acceptance are not explicitly listed in this document extract, the performance data provided is presented against these guidelines.
| Metric | Acceptance Criteria (Implicit from FDA Guidance) | Reported Performance (Cefazolin) |
|---|---|---|
| Essential Agreement (EA) % | High agreement with reference method. Deviations (VME, mE, ME) within acceptable limits. | 97.4% EA |
| Very Major Errors (VME) | Low (e.g., typically 95%) | 100% Reproducibility |
Note: The "N/A" for VME, ME, and mE under Essential Agreement indicates that these specific error types are separately reported under Category Agreement in the provided table, which is a common practice for AST system performance reporting.
2. Sample Size and Data Provenance:
- Test Set Sample Size: Not explicitly stated as a single number. The study mentions "fresh and stock clinical isolates, as well as a set of challenge strains." The quantitative performance metrics (EA, CA, Reproducibility) are derived from this test set.
- Data Provenance: The document does not specify the country of origin of the data. It indicates the study was an "external evaluation." It is implied to be prospective as it involves testing isolates with the VITEK® 2 AST-GN Cefazolin device and comparing it to a reference method.
3. Number of Experts and Qualifications:
Not applicable. This study evaluated an automated antimicrobial susceptibility test system (VITEK® 2) against a recognized reference method (CLSI broth microdilution). It did not involve human experts establishing ground truth through image interpretation or similar processes common in AI/Imaging studies.
4. Adjudication Method for the Test Set:
Not applicable. Ground truth for antimicrobial susceptibility testing is established by a standardized laboratory reference method (CLSI broth microdilution), not by consensus among human experts.
5. Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study:
No, an MRMC comparative effectiveness study was not done. This type of study is typically performed for AI systems that assist human readers in tasks like image interpretation. The VITEK® 2 system is an automated diagnostic device; its performance is compared to a laboratory reference standard, not to human readers' performance with and without AI assistance.
6. Standalone Performance:
Yes, a standalone performance evaluation was done. The reported performance metrics (Essential Agreement, Category Agreement, Reproducibility) represent the performance of the VITEK® 2 AST-GN Cefazolin system (algorithm only, as it's an automated test) compared to the CLSI broth microdilution reference method.
7. Type of Ground Truth Used:
The type of ground truth used was CLSI broth microdilution reference method, incubated at 16-24 hours. This is a widely accepted laboratory standard for determining antimicrobial susceptibility.
8. Sample Size for the Training Set:
Not applicable or not explicitly mentioned as a "training set" in the context of machine learning. This device is described as operating based on "microdilution minimum inhibitory concentration (MIC) technique," which suggests a deterministic algorithm rather than a machine learning model that undergoes "training." The system's rules or parameters would be pre-defined based on established microbiological principles, not trained on a large dataset in the way a deep learning model would be.
9. How the Ground Truth for the Training Set Was Established:
Not applicable for the reasons mentioned above (not a machine learning model with a distinct training phase requiring ground truth establishment from raw data). The "ground truth" equivalent for developing such a system would involve extensive research and validation against established microbiological methods like the CLSI broth microdilution method during its initial development and calibration.
§ 866.1645 Fully automated short-term incubation cycle antimicrobial susceptibility system.
(a)
Identification. A fully automated short-term incubation cycle antimicrobial susceptibility system is a device that incorporates concentrations of antimicrobial agents into a system for the purpose of determining in vitro susceptibility of bacterial pathogens isolated from clinical specimens. Test results obtained from short-term (less than 16 hours) incubation are used to determine the antimicrobial agent of choice to treat bacterial diseases.(b)
Classification. Class II (special controls). The special control for this device is FDA's guidance document entitled “Class II Special Controls Guidance Document: Antimicrobial Susceptibility Test (AST) Systems; Guidance for Industry and FDA.”