(45 days)
MRSASelect is a selective and differential chromogenic medium for the qualitative detection of nasal colonization of methicillin-resistant Staphylococcus aureus (MRSA) to aid in the prevention and control of MRSA infections in healthcare settings. The test can be performed on anterior nares specimens from patients and healthcare workers to screen for MRSA colonization. MRSASelect is not intended to diagnose MRSA infection nor to guide or monitor treatment of infection. Results can be interpreted after 18 - 28 hours incubation.
The Bio-Rad MRSASelect is a selective and differential chromogenic culture medium for the qualitative detection of MRSA from anterior nares specimens. Results can be interpreted after 18 - 28 hours incubation.
Here's an analysis of the acceptance criteria and study proving the device meets them, based on the provided text:
1. Table of Acceptance Criteria and Reported Device Performance
The document does not explicitly state pre-defined acceptance criteria for the performance metrics (sensitivity, specificity, PPV, NPV). However, it reports the device's performance, and since the 510(k) was cleared, it can be inferred that these reported values were deemed acceptable by the regulatory body.
| Performance Metric | Acceptance Criteria (Inferred) | Reported Device Performance (18-28 hours incubation) |
|---|---|---|
| Sensitivity (Sen) | Deemed acceptable by FDA | 100% |
| Specificity (Spec) | Deemed acceptable by FDA | 98% |
| PPV | Deemed acceptable by FDA | 86% |
| NPV | Deemed acceptable by FDA | 100% |
2. Sample Size Used for the Test Set and Data Provenance
- Sample Size: A total of 200 surveillance samples.
- Data Provenance: The study was conducted at "two geographically diverse hospitals" with "fresh anterior nares surveillance specimens." This indicates the data is prospective and originated from clinical settings, likely within the country where the Bio-Rad MRSASelect is seeking approval (France is the sponsor, but the 510(k) is for the US market, so the hospitals would likely be in the US or a similar regulatory region). The document doesn't explicitly state the country of origin but implies clinical relevance for the 510(k) submission.
3. Number of Experts Used to Establish Ground Truth for the Test Set and Qualifications
The document does not explicitly mention the number of experts or their qualifications for establishing the ground truth. It describes the ground truth process as "Routine culture was defined as isolation of Staphylococci on Trypticase Soy Agar with 5% blood, with identification confirmed by coagulase and Oxacillin susceptibility using E-Test." This implies standard laboratory procedures were followed, which are typically performed by trained medical laboratory scientists or microbiologists.
4. Adjudication Method for the Test Set
The document does not describe any specific adjudication method (like 2+1 or 3+1). The ground truth was established through a defined "routine culture" process, which is a laboratory standard rather than a subjective expert assessment requiring adjudication.
5. Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study
No, a Multi-Reader Multi-Case (MRMC) comparative effectiveness study was not done. This study evaluates a diagnostic aid where human readers interpret results, and the document describes a standalone diagnostic test (culture medium) where the output is directly observed (colony growth and color) rather than interpreted subjectively by multiple readers. The device performs the detection, not aids human interpretation of complex images.
6. Standalone Performance
Yes, a standalone performance study was done. The entire performance evaluation focuses on the Bio-Rad MRSASelect culture medium's ability to detect MRSA directly from samples, independent of human interpretation other than observing the results of the culture. The results (sensitivity, specificity, PPV, NPV) are reported for the device itself against the routine culture gold standard.
7. Type of Ground Truth Used
The ground truth used was routine culture and laboratory confirmation. Specifically:
- Isolation of Staphylococci on Trypticase Soy Agar with 5% blood.
- Identification confirmed by coagulase test.
- Oxacillin susceptibility confirmed using E-Test.
This is a robust and long-established method for confirming bacterial identification and antibiotic resistance.
8. Sample Size for the Training Set
The document does not mention a separate training set. The performance data provided is for the evaluation of the finished product, not for the development or training of the chromogenic medium formulation itself. Culture media are typically developed through iterative formulation and testing, but the 510(k) submission focuses on the final product's clinical performance.
9. How the Ground Truth for the Training Set Was Established
Since no separate training set is mentioned in the provided text, the method for establishing its ground truth is also not described.
§ 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).