(125 days)
Remel Spectra™ MRSA is a selective and differential chromogenic medium recommended for use in the qualitative detection of nasal colonization of methicillin-resistant Staphylococcocus aureus (MRSA) to aid in the prevention and control of MRSA in healthcare settings. The test is performed with anterior nares swab specimens from patients and healthcare workers to screen for MRSA colonization. Spectra™ MRSA is not intended to diagnose MRSA infection or to quide or monitor treatment for infections.
Remel Spectra™ MRSA is an opaque medium, which uses a novel chromogen that yields a denim-blue color as a result of phosphatase activity. This enzyme is present in all MRSA. To allow the medium to differentiate MRSA accurately, it contains a combination of antibacterial compounds designed to inhibit the growth of a wide variety of competitor organisms. Also included are compounds that encourage the production of MRSA pathogenicity marker, ensuring expression of the phosphatase enzyme and so providing enhanced sensitivity and specificity.
Here's a breakdown of the acceptance criteria and study details for the Remel Spectra™ MRSA device, based on the provided text:
1. Table of Acceptance Criteria and Reported Device Performance:
The document doesn't explicitly state pre-defined acceptance criteria in terms of specific percentages for sensitivity, specificity, or agreement. Instead, it presents the device's performance metrics as a comparison against established reference methods (traditional culture, Oxacillin MIC, and PBP2' testing). The implicit acceptance is that the device demonstrates comparable and high performance to these methods.
| Metric (vs. Traditional Culture) | Acceptance Criteria (Implied) | Reported Device Performance (Spectra™ MRSA at 24 hours vs. Traditional Culture at 48 hours) |
|---|---|---|
| % Agreement MRSA | High agreement | 95.2% (95% CI = 89.2–98.4%) |
| % Agreement Non-MRSA | High agreement | 99.1% (95% CI = 98.0-99.7%) |
| Overall Agreement | High agreement | 98.6% (95% Cl = 97.5-99.3%) |
| Metric (vs. Oxacillin MIC) | Acceptance Criteria (Implied) | Reported Device Performance (Spectra™ MRSA at 24 hours vs. Oxacillin MIC) |
|---|---|---|
| Sensitivity | High sensitivity | 95.4% (95% CI = 89.6-98.5%) |
| Specificity | High specificity | 99.7% (95% CI = 98.9-100%) |
| Overall Agreement | High agreement | 99.1% (95% CI = 98.1-99.6%) |
| Positive Predictive Value (PPV) | High PPV | 98.1% (95% Cl = 93.4-99.8%) |
| Negative Predictive Value (NPV) | High NPV | 99.2% (95% Cl = 98.2–99.8%) |
| Metric (vs. PBP2') | Acceptance Criteria (Implied) | Reported Device Performance (Spectra™ MRSA at 24 hours vs. PBP2') |
|---|---|---|
| Sensitivity | High sensitivity | 95.4% (95% CI = 89.6-98.5%) |
| Specificity | High specificity | 99.7% (95% CI = 98.9-100%) |
| Overall Agreement | High agreement | 99.1% (95% CI = 98.1-99.6%) |
| Positive Predictive Value (PPV) | High PPV | 98.1% (95% Cl = 93.4-99.8%) |
| Negative Predictive Value (NPV) | High NPV | 99.2% (95% Cl = 98.2–99.8%) |
2. Sample Size Used for the Test Set and Data Provenance:
- Sample Size: 767 prospective anterior nare surveillance specimens.
- Data Provenance: The specimens were collected from "four geographically diverse regions of the United States." The study was "prospective."
3. Number of Experts Used to Establish the Ground Truth for the Test Set and Their Qualifications:
The document does not specify the number or qualifications of experts directly. The ground truth was established through a combination of traditional laboratory methods:
- Identification of S. aureus: Latex agglutination test or a biochemical identification system. These are standard laboratory procedures usually performed by trained laboratory technologists/scientists.
- Susceptibility Testing (for MRSA confirmation): Antibiotic gradient method for oxacillin and the Oxoid PBP2' test for detection of penicillin-binding protein 2a. Again, these are standard laboratory tests typically interpreted by trained personnel.
4. Adjudication Method for the Test Set:
The document does not describe an explicit "adjudication method" in the sense of multiple human readers independently assessing the Spectra™ MRSA results and then resolving discrepancies. Instead, the Spectra™ MRSA results were directly compared to the established ground truth obtained from standard laboratory methods (traditional culture, identification, and susceptibility testing).
5. If a Multi Reader Multi Case (MRMC) Comparative Effectiveness Study Was Done:
No, an MRMC comparative effectiveness study involving human readers with and without AI assistance was not done. This device is a culture medium, not an AI diagnostic tool that assists human readers.
6. If a Standalone (i.e., algorithm only without human-in-the-loop performance) Was Done:
Yes, the primary clinical accuracy study evaluated the standalone performance of the Spectra™ MRSA chromogenic medium. Its direct output (denim-blue colonies indicating MRSA) was compared against the gold standard laboratory methods. There is no "human-in-the-loop" component for this specific device beyond standard laboratory interpretation of culture plates or biochemical/susceptibility tests.
7. The Type of Ground Truth Used:
The ground truth was established through a combination of traditional microbiology laboratory methods, including:
- Traditional Culture: Tryptic Soy Agar with 5% Sheep Blood Agar (TSA with 5% SBA).
- Biochemical Identification: Latex agglutination test or a biochemical identification system for S. aureus.
- Susceptibility Testing/Pathogen Marker Detection: Antibiotic gradient method for oxacillin and the Oxoid PBP2' test for detection of penicillin-binding protein 2a.
- The combination of these methods serves as the expert consensus-based laboratory standard for identifying and confirming MRSA colonization.
8. The Sample Size for the Training Set:
The document does not explicitly mention a separate "training set" or "training data" for this device. As a chromogenic culture medium, its performance is based on its inherent biochemical and microbiological properties, not on a machine learning model that requires training data. The "Summary of Performance Data" describes a clinical validation study (test set).
9. How the Ground Truth for the Training Set Was Established:
Since there is no mention of a separate training set for a machine learning model, this question is not applicable to the development of this specific device. The device's formulation inherently relies on known biochemical reactions and selective agents, rather than being "trained" on data.
§ 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).