(57 days)
VITEK® 2 Streptococcus Ampicillin is designed for antimicrobial susceptibility testing of Streptococcus species. VITEK® 2 Streptococcus Ampicillin is a quantitative test 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. Ampicillin has been shown to be active against the microorganisms listed below: Beta-hemolytic group Streptococcus species Viridans group Streptococcus species. The VITEK® 2 Antimicrobial Susceptibility Test (AST) is intended to be used with the VITEK® 2 System for the automated quantitative or qualitative susceptibility testing of isolated colonies for the most clinically significant aerobic gram-negative bacilli, Staphylococcus spp., Enterococcus spp., Streptococcus spp. and clinically significant yeast.
VITEK® 2 AST-ST Ampicillin is designed for antimicrobial susceptibility testing of Streptococcus species. VITEK® 2 AST-ST Ampicillin is a quantitative test 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. The antimicrobial agent presented in VITEK® 2 AST Cards is in concentrations equivalent by efficacy to standard method concentrations in mcg/ml. The VITEK® 2 AST Cards are essentially miniaturized versions of the doubling dilution technique for determining the minimum inhibitory concentration (MIC) microdilution methodology. The bacterial isolate to be tested is diluted to a standardized concentration in 0.45 - 0.50% 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 and sealing operation. The VITEK® 2 monitors the growth of each well in the card over a defined period of time (up to 36 hours for yeast). At the completion of the incubation cycle, a report is generated that contains the MIC value along with the interpretive category result for each antimicrobial contained on the card.
Here's a breakdown of the acceptance criteria and study details for the VITEK® 2 AST-ST Ampicillin, based on the provided 510(k) summary:
1. Table of Acceptance Criteria and Reported Device Performance
The acceptance criteria for Antimicrobial Susceptibility Test (AST) systems are typically defined in FDA guidance documents. While the exact numerical criteria aren't explicitly stated as a table in this document, the summary refers to "acceptable performance" and the "FDA Class II Special Controls Guidance Document: Antimicrobial Susceptibility Test (AST) Systems; Guidance for Industry and FDA. Issued August. 28, 2009."
Based on the reported performance, we can infer the acceptance criteria for Essential Agreement (EA) and Category Agreement (CA).
| Performance Metric | Acceptance Criteria (Inferred) | Reported Device Performance |
|---|---|---|
| Overall Essential Agreement | Likely ≥ 90% (Common AST criteria) | 99.1% |
| Overall Category Agreement | Likely ≥ 90% (Common AST criteria) | 97.0% |
| Reproducibility | Acceptable | Acceptable |
| Quality Control | Acceptable | Acceptable |
Note: The specific numerical acceptance criteria (e.g., "not less than 90%") for Essential and Category Agreement according to the referenced FDA guidance are not explicitly stated in this document but are standard for AST devices.
2. Sample Size Used for the Test Set and Data Provenance
- Test Set Description: The external evaluation was conducted with:
- Fresh clinical isolates
- Stock clinical isolates
- A set of challenge strains
- Sample Size: The document does not explicitly state the total number of isolates (sample size) used in the external evaluation (test set).
- Data Provenance: The document does not explicitly state the country of origin of the data. It mentions an "external evaluation," which typically implies data collected from multiple sites beyond the manufacturer's internal labs. The study was conducted using both fresh and stock clinical isolates, implying a retrospective and prospective mix, as stock isolates are typically retrospective, while fresh isolates would be prospective.
3. Number of Experts Used to Establish the Ground Truth for the Test Set and Qualifications of Those Experts
- The ground truth was established by comparing the device's performance to the CLSI broth microdilution reference method.
- This is a laboratory-based reference method, not typically established by individual "experts" in the sense of physicians or radiologists. Rather, it's a standardized laboratory procedure performed by trained microbiologists following CLSI guidelines. Therefore, the concept of "number of experts" with specific clinical qualifications for establishing this kind of ground truth is not directly applicable.
4. Adjudication Method for the Test Set
- Since the ground truth is the CLSI broth microdilution reference method, an "adjudication method" involving experts for discrepancies is generally not applicable in the same way it would be for image-based diagnostics where human interpretation is the primary ground truth. The comparison is between the device's MIC/interpretive category and the reference method's MIC/interpretive category. Discrepancies would be analyzed against the standard, but not typically "adjudicated" by multiple rounds of human expert review.
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 investigates the impact of an AI system on human reader performance, which is relevant for diagnostic imaging or clinical decision support tools. This device is an automated laboratory instrument measuring antimicrobial susceptibility, where the comparison is against an established reference method, not against human interpretation of the same data.
6. If a Standalone (i.e., algorithm only without human-in-the-loop performance) Was Done
- Yes, a standalone performance evaluation was done. The VITEK® 2 AST-ST Ampicillin device (an automated laboratory instrument) was compared directly to the CLSI broth microdilution reference method. This is a standalone performance evaluation of the device itself, without a human "in-the-loop" for interpreting the results, other than monitoring the instrument and interpreting its final output (MIC and interpretive category). The VITEK 2 system automatically fills, seals, and places the card, and monitors growth, generating an MIC value and interpretive category result.
7. The Type of Ground Truth Used
- The ground truth used was the CLSI broth microdilution reference method. This is an industry-standard, well-established laboratory method for determining minimum inhibitory concentrations (MICs) of antimicrobial agents.
8. The Sample Size for the Training Set
- The document does not provide information on the sample size used for the training set. It describes the "external evaluation" as the test set for substantial equivalence. For a device like this, the "training" (if an AI/machine learning component were involved) would likely involve a large historical dataset of MIC values used to develop and refine the algorithms for interpreting growth patterns into MICs. This detail is not present in the 510(k) summary.
9. How the Ground Truth for the Training Set Was Established
- As the document does not specify a training set or its sample size, it does not describe how the ground truth for any potential training set was established. Similar to the test set, any ground truth used during the development or "training" phase would almost certainly have been derived from the CLSI broth microdilution reference method or similar gold standard laboratory methods.
§ 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.”