(234 days)
The BD Phoenix™ Automated Microbiology System is intended for the in vitro rapid identification (ID) and quantitative determination of antimicrobial susceptibility by minimal inhibitory concentration (MIC) of Gram Negative aerobic and facultative anaerobic bacteria belonging to the family Enterobacteriaceae and non-Enterobacteriaceae
The BD Phoenix™ Automated Microbiology System is intended for in vitro quantitative determination of antimicrobial susceptibility by minimal inhibitory concentration (MIC) of most Gram-negative aerobic and facultative anaerobic bacteria isolates from pure culture for Enterobacteriaceae and Non-Enterobacteriaceae and most Gram-positive bacteria isolates from pure culture belonging to the genera Staphylococcus, Enterococcus and Streptococcus.
Imipenem has been shown to be active in vitro against most strains of microorganisms listed below, as described in the FDA-approved package insert for this antimicrobial agent.
Active In Vitro and in Clinical Infections Against: Acinetobacter spp. Citrobacter spp. Enterobacter cloacae Escherichia coli Klebsiella spp.
Pseudomonas aeruginosa Serratia marcescens
The BD Phoenix Automated Microbiology System (Phoenix System) is an automated system for the rapid identification (ID) and antimicrobial susceptibility testing (AST) of clinically relevant bacterial isolates. The system includes the following components:
- . BD Phoenix instrument and software.
- BD Phoenix panels containing biochemicals for organism ID testing and antimicrobial . agents for AST determinations.
- BD Phoenix ID Broth used for performing ID tests and preparing AST Broth inoculum. ●
- . BD Phoenix AST Broth used for performing AST tests only.
- BD Phoenix AST Indicator solution added to the AST Broth to aid in bacterial growth . determination.
The Phoenix panel is a sealed and self-inoculating molded polystyrene trav with 136 micro-wells containing dried reagents. Organisms for susceptibility testing must be a pure culture and preliminarily identified as a Gram-negative or Gram-positive isolate. Phoenix panels are inoculated with a specified organism density and placed into the instrument. Inoculum for use with the Phoenix system may be prepared either manually or may be automated using the BD Phoenix™ AP System.
The Phoenix AST method is a broth based microdilution test. The Phoenix System utilizes a redox indicator for the detection of organism growth in the presence of an antimicrobial agent. Measurements of changes to the indicator as well as bacterial turbidity are used in the determination of bacterial growth. Each AST panel configuration contains several antimicrobial agents with a wide range of two-fold doubling dilution concentrations.
The instrument houses the panels where they are continuously incubated at a nominal temperature of 35° ± 1°C. The instrument takes readings of the panels every 20 minutes. The readings are interpreted to give an identification of the isolate, minimum inhibitory concentration (MIC) values and category interpretations, S. I, R or N (susceptible, intermediate, resistant or not susceptible).
This document describes the validation study for the BD Phoenix™ Automated Microbiology System's ability to determine antimicrobial susceptibility for Imipenem (0.0625-32 µg/mL) against Gram-negative organisms.
1. Table of Acceptance Criteria and Reported Device Performance
| Performance Metric | Acceptance Criteria (Implied by FDA Guidance) | Reported Device Performance |
|---|---|---|
| Clinical Isolates | ||
| Essential Agreement (EA) | Not explicitly stated but typically > 90% | 94.6% (n=1348) |
| Category Agreement (CA) | Not explicitly stated but typically > 90% | 95.3% (n=1348) |
| Site Reproducibility | > 95% (+/- 1 dilution) | > 95% (+/- 1 dilution) |
Note: The FDA guidance "Class II Special Controls Guidance Document: Antimicrobial Susceptibility Test (AST) Systems" (August 28, 2009) implicitly sets the acceptance criteria through its recommendations for demonstrating substantial equivalence. The reported values meet or exceed these typical expectations.
2. Sample Size Used for the Test Set and Data Provenance
- Test Set Sample Size: The document reports n=1348 for clinical isolates used in the Essential Agreement (EA) and Category Agreement (CA) calculations for Imipenem. The number of challenge isolates is not separately reported but is included in the overall performance summary.
- Data Provenance:
- Country of Origin: United States. The clinical studies were conducted "across multiple geographically diverse sites across the United States."
- Retrospective or Prospective: Not explicitly stated, but the description of "clinical, stock and challenge isolates were tested" suggests a mix, likely involving prospective testing of newly acquired clinical isolates and retrospective testing of archived stock and challenge isolates.
3. Number of Experts Used to Establish the Ground Truth for the Test Set and Qualifications of Those Experts
There is no mention of "experts" in the context of establishing ground truth for AST systems. The ground truth (reference method) for antimicrobial susceptibility testing is a standardized laboratory procedure, not an expert opinion.
4. Adjudication Method for the Test Set
Not applicable. The ground truth is established by a standardized reference method (CLSI broth microdilution), not through expert adjudication. Discrepancies between the device and the reference method are analyzed as part of the performance evaluation (e.g., major errors, very major errors), but not "adjudicated" in the sense of a consensus review.
5. If a Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study Was Done
No, a Multi-Reader Multi-Case (MRMC) comparative effectiveness study was not done. This type of study is typically used for image-based diagnostic systems where human interpretation is involved. For an automated microbiology system that measures MIC values, the comparison is against a reference laboratory method rather than human readers.
6. If a Standalone (i.e., algorithm only without human-in-the-loop performance) Was Done
Yes, the study presents standalone performance. The BD Phoenix™ Automated Microbiology System is an automated system where the "algorithm only" (the instrument and its software) determines the MIC values and categorical interpretations. Human intervention is limited to sample preparation and instrument loading; the interpretation itself is automated.
7. The Type of Ground Truth Used
The ground truth used was the CLSI reference broth microdilution method (AST panels prepared according to CLSI M7). This is a standardized laboratory method for determining antimicrobial susceptibility. For challenge set isolates, "expected results" were used, which are typically pre-determined and validated MIC values for specific strains.
8. The Sample Size for the Training Set
The document does not provide information on the sample size for the training set. The described studies focus on the validation performance of the device against the reference standard. The BD Phoenix™ system would have been developed and trained (or "calibrated") using a large, undisclosed dataset of bacterial isolates with known susceptibilities, but this information is not part of this 510(k) summary.
9. How the Ground Truth for the Training Set Was Established
The document does not provide information on how the ground truth for the training set was established. Similar to the test set, it would have been established using a standardized reference method, most likely the CLSI broth microdilution method, during the development phase of the BD Phoenix™ system.
§ 866.1645 Fully automated short-term incubation cycle antimicrobial susceptibility system.
(a)
Identification. A fully automated short-term incubation cycle antimicrobial susceptibility system is a device that incorporates concentrations of antimicrobial agents into a system for the purpose of determining in vitro susceptibility of bacterial pathogens isolated from clinical specimens. Test results obtained from short-term (less than 16 hours) incubation are used to determine the antimicrobial agent of choice to treat bacterial diseases.(b)
Classification. Class II (special controls). The special control for this device is FDA's guidance document entitled “Class II Special Controls Guidance Document: Antimicrobial Susceptibility Test (AST) Systems; Guidance for Industry and FDA.”