(241 days)
MRSASelect™ is a selective and differential chromogenic medium for the qualitative detection of methicillin resistant Staphylococcus aureus (MRSA) from skin and soft-tissue wound specimens. The MRSASelect™ is indicated for use in conjunction with other laboratory tests and clinical data available to aid in the identification and diagnosis of MRSA from patients with skin and soft-tissue infections. Concomitant cultures and susceptibility testing are necessary for all skin and soft-tissue wound specimens. MRSASelect™ is not intended to guide, or monitor treatment for MRSA infection, or provides results of susceptibility to methicillin. Results can be interpreted after 18 to 28 hours incubation.
The Bio-Rad MRSASelect is a selective and differential chromogenic culture medium for the qualitative detection of MRSA from skin or soft-tissue wound specimens. Results can be interpreted after 18 - 28 hours incubation.
The provided document describes the Bio-Rad MRSASelect - Wound Specimens, a chromogenic medium for detecting methicillin-resistant Staphylococcus aureus (MRSA) from skin and soft-tissue wound specimens.
Here's an analysis based on the provided text:
1. Table of Acceptance Criteria and Reported Device Performance:
The document does not explicitly state "acceptance criteria" as distinct numerical targets. However, based on the performance data presented, the implicit acceptance criteria would be the measured specificity and sensitivity values.
| Performance Metric | Acceptance Criteria (Implicit from Study Results) | Reported Device Performance |
|---|---|---|
| Specificity | N/A (Expected to be high) | 99.4% (95% CI: [98.5, 99.8]) |
| Sensitivity | N/A (Expected to be high) | 91.7% (95% CI: [87.3, 94.7]) |
| Overall Agreement | N/A (Expected to be high) | 97.6% (95% CI: [96.3, 98.4]) |
| Reproducibility | N/A (Expected to be high) | 100% |
| Cross-reactivity | No cross-reactivity expected | Not observed |
2. Sample size used for the test set and the data provenance:
- Sample Size for Test Set: 943 clinical skin and soft-tissue wound samples.
- Data Provenance: The samples were collected and tested at four clinical laboratories in the United States. The study is prospective in the sense that samples were collected and tested for the purpose of this evaluation, but the clinical context (e.g., patient demographics, recruitment methods) typical of a detailed prospective study are not fully elaborated.
3. Number of experts used to establish the ground truth for the test set and the qualifications of those experts:
The document does not specify the number of experts or their qualifications used to establish the ground truth for the clinical test set. It mentions "routine culture and identification" as the comparator method.
4. Adjudication method (e.g. 2+1, 3+1, none) for the test set:
The document does not describe an adjudication method for disagreements, as it relies on a "routine culture and identification" method as the comparator. The ground truth was established by confirming positive samples from TSA or TSB with Gram stain, Pastorex™ Staph Plus, and mecA mediated oxacillin resistance using a Cefoxitin disk.
5. If a multi-reader multi-case (MRMC) comparative effectiveness study was done, If so, what was the effect size of how much human readers improve with AI vs without AI assistance:
This device is a culture medium, not an AI-assisted diagnostic tool. Therefore, an MRMC comparative effectiveness study was not performed, and the concept of "human readers improving with AI assistance" does not apply.
6. If a standalone (i.e. algorithm only without human-in-the-loop performance) was done:
The device is a culture medium that provides a qualitative visual result (pink colonies for MRSA). While human interpretation is involved in reading the results, the performance data presented (specificity, sensitivity) represents the standalone performance of the medium in detecting MRSA from samples, with a human interpreting the outcome. There is no "algorithm" involved in the sense of an AI model.
7. The type of ground truth used (expert consensus, pathology, outcomes data, etc.):
The ground truth for the clinical study (Method Comparison) was established by a combination of standard microbiological methods, referred to as "Routine Culture & TSB." This involved:
- Trypticase Soy Agar (TSA) with 5% Sheep's Blood
- Tryptic Soy Broth (TSB) with 6.5% NaCl
- Confirmation of positive samples with Gram stain, Pastorex™ Staph Plus, and mecA mediated oxacillin resistance using a 30 ug/mL Cefoxitin disk.
8. The sample size for the training set:
The document does not mention a separate "training set" as this is a traditional diagnostic medium validation, not an AI model development. However, several analytical studies were performed:
- Interfering Substances: Samples of common topical agents inoculated with MRSA.
- Cross-Reactivity Testing: 35 bacterial and fungal strains.
- Analytical Sensitivity: 102 strains of MRSA (including USA100, 200, 300, 500, 600, and 1000).
- Reproducibility: A panel of 6 organisms (MRSA, MSSA, S. epidermidis).
9. How the ground truth for the training set was established:
For the analytical studies (which could be considered analogous to internal validation or characterization):
- Interfering Substances: Ground truth was based on expected growth/inhibition of known MRSA strains in the presence of various agents.
- Cross-Reactivity Testing: Ground truth was based on the known identity of the 35 bacterial and fungal strains inoculated.
- Analytical Sensitivity: Ground truth was based on the known identity and concentration of the 102 characterized MRSA strains used.
- Reproducibility: Ground truth was based on the known identity of the 6 organisms in the panel.
§ 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).