(20 days)
To determine bacterial antimicrobial agent susceptibility. 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 according to the Package Insert. Additionally, the panels may be incubated in and read by a MicroScan® WalkAway instrument. This particular submission is for the addition of instrument read capability of the antimicrobial Ceftriaxone, at concentrations of 0.015 to 8 mcg/ml on the MicroScan MICroSTREP plus® Panel. The organisms which may be used for Ceftriaxone susceptibility testing in this panel are: Streptococcus pneumoniae Streptococcus pyogenes viridans group streptococci
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 according to the Package Insert. The antimicrobial susceptibility tests are miniaturizations of the broth dilution susceptibility test. 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) and buffered with 50 mM HEPES, after inoculation of the broth with a standardized suspension of the organism in saline. 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. Additionally, the panels may be incubated in and read by a MicroScan WalkAway instrument.
1. Acceptance Criteria and Reported Device Performance
| Acceptance Criteria | Reported Device Performance (Ceftriaxone) |
|---|---|
| Essential Agreement (Instrument read vs. Expected Result) | 99% |
| Reproducibility (Instrument to instrument) | Acceptable |
| Precision (Within instrument) | Acceptable |
| Quality Control | Acceptable |
2. Sample Size and Data Provenance
- Test Set Sample Size: Not explicitly stated, however, the study involved "stock and CDC Challenge strains." The specific number of isolates used for evaluation is not provided.
- Data Provenance: Not explicitly stated, though the use of "CDC Challenge strains" suggests a potentially US-centric origin or at least strains relevant to US public health surveillance. The study appears to be prospective, as it's a comparison to "expected results determined before the evaluation."
3. Number and Qualifications of Experts for Ground Truth
- Not applicable as the ground truth was not established by human experts in the traditional sense of image interpretation or clinical diagnosis. The "expected result" was generated using a CLSI frozen Reference Panel, which is a standardized laboratory method.
4. Adjudication Method
- Not applicable, as the evaluation was a comparison against a standardized reference panel, not a consensus among human experts.
5. Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study
- No, a multi-reader multi-case (MRMC) comparative effectiveness study was not performed. This study focused on the standalone performance of the instrument read method against a reference standard. The document describes adding "instrument read capability," not assisting human readers.
6. Standalone (Algorithm Only) Performance
- Yes, a standalone performance study was performed. The evaluation specifically compared the "proposed instrument read method" to "Expected Results" generated by a CLSI frozen Reference Panel, indicating an algorithm-only evaluation without human-in-the-loop performance being the primary focus. The purpose was to confirm the acceptability of the instrument's reading of the MICroSTREP plus Panel with Ceftriaxone.
7. Type of Ground Truth Used
- Reference Standard: The ground truth was established by an "expected result generated on a CLSI frozen Reference Panel," as defined in the FDA guidance document "Class II Special Controls Guidance Document: Antimicrobial Susceptibility Test (AST) Systems; Guidance for Industry and FDA." This represents a standardized, laboratory-based reference method for determining antimicrobial susceptibility.
8. Sample Size for the Training Set
- The document does not explicitly mention a separate "training set" as it would for a machine learning model. The evaluation compares the instrument's performance against a reference standard, suggesting that the instrument's "reading" capabilities were either pre-calibrated or designed based on existing knowledge of AST methods, rather than being "trained" on a specific dataset in the modern AI sense. The stock and CDC Challenge strains were used for the evaluation of the instrument's performance.
9. How Ground Truth for the Training Set Was Established
- Not applicable given the nature of the device (an automated reader for a standardized test panel) and the absence of an explicit "training set" in the context of an AI model. The reference for performance was a CLSI frozen Reference Panel, which represents an established and validated method for determining antimicrobial susceptibility.
§ 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).