(50 days)
The MicroScan® MICroSTREP plus® Panel is used to determine quantitative and/or qualitative antimicrobial agent susceptibility of colonies grown on solid media of aerobic streptococci including Streptococcus pneumoniae. After inoculation, panels are incubated for 20 -24 hours at 35°C +/- 1°C in a non-CO2 incubator, and read visually. Alternatively, the panels can be incubated in and read by the MicroScan® WalkAway System, according to the Package insert.
This particular submission is for the addition of the antimicrobial agent Linezolid, at concentrations of 0.12 to 16 ug/mL, to the test panel.
The organisms which may be used for Linezolid susceptibility testing in this panel are:
Streptococcus pneumoniae including multi-drug resistant strains
Streptococcus pyogenes
Streptococcus agalactiae
Viridans group streptococci
MicroScan MICroSTREP plus panels are designed for use in determining quantitative and/or qualitative antimicrobial agent susceptibility of colonies grown on solid media of . aerobic streptococci, including Streptococcus pneumoniae.
The antimicrobial susceptibility tests are miniaturizations of the broth dilution susceptibility test that have been diluted in water and dehydrated. Various antimicrobial agents are diluted in water, buffer or minute concentrations of broth to concentrations bridging the range of clinical interest. Panels are rehydrated with 115 µl Mueller-Hinton broth supplemented with 2-5% lysed horse blood (LHB), after inoculation of the broth with a standardized suspension of the organism. After incubation in a non-CO2 incubator for 20-24 hours, the minimum inhibitory concentration (MIC) for the test organism is manually read by observing the lowest antimicrobial concentration showing inhibition of growth. Alternatively, the panel can be incubated in and read by the MicroScan® WalkAway System.
Here's an analysis of the acceptance criteria and study detailed in the provided documents, structured according to your request:
1. Table of Acceptance Criteria and Reported Device Performance
| Acceptance Criteria | Reported Device Performance (Linezolid) |
|---|---|
| Overall Essential Agreement with CLSI frozen Reference Panel | 97.2% |
| Reproducibility | Acceptable reproducibility and precision |
| Quality Control | Acceptable results |
2. Sample Size Used for the Test Set and Data Provenance
The document mentions "fresh and stock Efficacy isolates and stock Challenge strains" for the external evaluation. However, it does not explicitly state the specific number of isolates or strains used for either the efficacy or challenge testing.
- Data Provenance: The study was an "external evaluation," implying it was conducted outside of the manufacturer's immediate control but within a regulated framework, comparing the device to a CLSI frozen Reference panel. The document does not specify the country of origin but implies a standard reference method commonly used in the US (CLSI). It is a retrospective evaluation as it uses established isolates.
3. Number of Experts Used to Establish Ground Truth for the Test Set and Their Qualifications
- The document states that "Challenge strains were compared to Expected Results determined prior to the evaluation." This implies that the "Expected Results" serve as the ground truth for the challenge strains.
- The number of experts and their specific qualifications are not mentioned in the provided text. The ground truth for the reference panel itself is implicitly a consensus from standard methodologies (CLSI).
4. Adjudication Method for the Test Set
- The document implies a direct comparison of the MicroScan MICroSTREP plus Panel's performance against a CLSI frozen Reference panel.
- For challenge strains, performance was compared to "Expected Results."
- No specific multi-reader adjudication method (e.g., 2+1, 3+1) is described for the test set. The comparison is against established reference values.
5. If a Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study Was Done
- No, an MRMC comparative effectiveness study involving human readers is not described in these documents. The study focuses on the performance of the automated/semi-automated AST system against a reference method. The document mentions reproducibility testing with different read methods (manual and WalkAway™ instrument), but this refers to the device's consistency, not the improvement of human readers with AI assistance.
6. If a Standalone (Algorithm Only Without Human-in-the-Loop Performance) Was Done
- Yes, a standalone performance study was done. The device itself (MicroScan MICroSTREP plus Panels) is assessed for its ability to determine antimicrobial susceptibility. The "manual" read method mentioned in reproducibility testing still refers to reading the panel results, not a human interpretation divorced from the device's output. The "WalkAway™ instrument" automatically reads the panel, which is a standalone function of the device system.
7. The Type of Ground Truth Used
- The primary ground truth used is a CLSI frozen Reference Panel. For challenge strains, "Expected Results" determined prior to the evaluation were used, which would also be based on established reference methods. This falls under expert consensus derived from standardized laboratory procedures.
8. The Sample Size for the Training Set
- The document does not provide information on the sample size used for the training set. The focus is on the performance evaluation of the device as submitted. This type of device (AST panel) typically relies on biochemical principles and established MIC ranges, rather than deep learning models that require distinct training sets in the same way an AI image analysis algorithm would.
9. How the Ground Truth for the Training Set Was Established
- Given that the document does not mention a distinct "training set" in the context of machine learning, the question of how its ground truth was established is not applicable. The device's development would be based on established microbiological principles for determining MICs, where the "ground truth" is defined by standard reference methods like those outlined by CLSI.
§ 866.1640 Antimicrobial susceptibility test powder.
(a)
Identification. An antimicrobial susceptibility test powder is a device that consists of an antimicrobial drug powder packaged in vials in specified amounts and intended for use in clinical laboratories for determining in vitro susceptibility of bacterial pathogens to these therapeutic agents. Test results are used to determine the antimicrobial agent of choice in the treatment of bacterial diseases.(b)
Classification. Class II (performance standards).