(304 days)
Remel Spectra™ VRE is a selective and differential chromogenic medium, containing 6 µg/ml of vancomycin, intended for use in the qualitative detection of gastrointestinal colonization with vancomycin-resistant Enterococcus faecium and Enterococcus faecalis (VRE) to aid in the prevention and control of VRE in healthcare settings. The test is performed with rectal swab and fecal specimens from patients to screen for VRE colonization. Spectra™ VRE is not intended to diagnose VRE infection or to guide or monitor treatment for infections. Subculture to non-selective media (e.g. Tryptic Soy Agar with 5% sheep blood) is needed for further identification, susceptibility testing, and epidemiological typing.
Remel Spectra™ VRE is an opaque medium allowing differentiation of vancomycin-resistant E. faecium from vancomycin-resistant E. faecalis by incorporation of two chromogens that are targeted by phosphatase and agalactosidase. The action of these enzymes on the chromogens results in a build-up of color within the colony. The presence of phosphatase enzymes in both E. faecium and E. faecalis results in a light blue or blue colony. However, E. faecium also produces a-galactosidase, resulting in a mix of blué and pink chromophores within the bacterium producing navy blue or pink-purple colonies, which are distinquished from the light blue or blue E. faecalis colonies. Additional antibiotics. in combination with vancomycin, are present to suppress the growth of competing flora including E. gallinarum and E. casseliflavus, both of which are intrinsically resistant to vancomycin, possessing the chromosomally encoded VanC resistance mechanism.
The information provided describes the performance of the Spectra™ VRE device, a chromogenic medium for detecting VRE colonization. Here's a breakdown of the acceptance criteria and study details:
1. Table of Acceptance Criteria and Reported Device Performance
The document doesn't explicitly state "acceptance criteria" as a section, but rather presents the overall agreement percentages for the device compared to conventional methods. The implicit acceptance criteria would likely be high concordance with established methods for both positive and negative results, along with robust detection of the target organisms.
| Metric | Acceptance Criteria (Implicit) | Reported Device Performance (Spectra™ VRE vs. Conventional Methods) |
|---|---|---|
| Overall Performance | High agreement | Positive % Agreement: 99.1% (218/220) |
| Negative % Agreement: 99.8% (408/409) | ||
| VR-E. faecium Detection | High agreement | Positive % Agreement: 99.0% (189/191) |
| Negative % Agreement: 99.8% (437/438) | ||
| VR-E. faecalis Detection | High agreement | Positive % Agreement: 100% (29/29) |
| Negative % Agreement: 100% (600/600) | ||
| VRE Recovery (Spectra™ VRE vs. BEAV) | Higher or similar recovery | Spectra™ VRE: 99.1% (218/220) |
| BEAV: 95.5% (210/220) | ||
| Interfering Substances | Minimal interference | Some substances (e.g., blood, Pepto-Bismol®) may reduce recovery |
| Reproducibility | 100% consistency | 100% of tested strains produced expected results at 24 hours |
2. Sample Size Used for the Test Set and Data Provenance
- Sample Size: 623 prospective rectal swab and fecal surveillance specimens (yielding 629 data points).
- Data Provenance: The study was conducted at "three geographically diverse regions of the United States," indicating a multi-site prospective study within the US. The data is prospective.
3. Number of Experts Used to Establish the Ground Truth for the Test Set and Qualifications of Those Experts
The document does not specify the "number of experts" or their "qualifications." It states that suspect VRE isolates were evaluated using:
- Vitek® 2 system
- Biochemical tests
- Antibiotic gradient method for vancomycin MIC determination
This suggests laboratory personnel following established microbiology protocols, rather than individual expert adjudication in the traditional sense of, for example, multiple radiologists reviewing images.
4. Adjudication Method for the Test Set
The document does not describe an adjudication method in the context of resolving discrepancies between multiple readers or interpretations. The ground truth was established by a combination of standard laboratory methods (Vitek® 2, biochemical tests, MIC determination), which inherently provide a definitive result without a need for "adjudication" between conflicting interpretations by multiple individuals.
5. If a Multi Reader Multi Case (MRMC) Comparative Effectiveness Study was Done
No, an MRMC comparative effectiveness study was not done. The study compares the performance of the Spectra™ VRE medium to a conventional culture method (Bile Esculin Azide Agar with Vancomycin), not the comparative effectiveness of human readers with or without AI assistance. The interpretation of both the Spectra™ VRE and the conventional method is described as "Manual, visual," indicating human interpretation of culture plates, but not a study designed to measure the impact of AI assistance on human performance.
6. If a Standalone (i.e., algorithm only without human-in-the-loop performance) was Done
This is an in vitro diagnostic (IVD) device, specifically a culture medium. Its performance is inherent to how well it grows and differentiates bacteria under manual, visual interpretation. There is no "algorithm" in the sense of artificial intelligence that would perform autonomously. Therefore, the concept of a "standalone" algorithm performance (without human-in-the-loop) as understood in AI/ML medical devices does not apply here. The performance described is the standalone performance of the medium itself when interpreted manually.
7. The Type of Ground Truth Used
The ground truth was established by a combination of:
- Conventional Culture: Growth on Bile Esculin Azide Agar with 6 µg/ml Vancomycin (BEAV) after 48 hours incubation.
- Identification and Susceptibility Testing: Suspect isolates were further evaluated using the Vitek® 2 system, biochemical tests, and an antibiotic gradient method for vancomycin Minimum Inhibitory Concentration (MIC) to confirm VRE (specifically E. faecium and E. faecalis) with MICs >256 µg/ml.
This represents a form of "reference standard" based on established microbiology laboratory methods for identification and antimicrobial susceptibility testing.
8. The Sample Size for the Training Set
The document does not mention a "training set" or "training data" as this is not an artificial intelligence/machine learning device. The development of the chromogenic medium would involve laboratory R&D, but not in the sense of training an algorithm on a dataset.
9. How the Ground Truth for the Training Set Was Established
As there is no "training set" in the context of an AI/ML device, this question is not applicable. The development of the medium would rely on scientific principles of microbiology and chromogenic reactions to achieve the desired differentiation.
§ 866.1700 Culture medium for antimicrobial susceptibility tests.
(a)
Identification. A culture medium for antimicrobial susceptibility tests is a device intended for medical purposes that consists of any medium capable of supporting the growth of many of the bacterial pathogens that are subject to antimicrobial susceptibility tests. The medium should be free of components known to be antagonistic to the common agents for which susceptibility tests are performed in the treatment of disease.(b)
Classification. Class II (performance standards).