(249 days)
The iCubate iC-GPC Assay for use on the iC-System is a qualitative, multiplexed, in vitro diagnostic test for the detection and identification of potentially pathogenic gram positive bacteria, which may cause bloodstream infection (BSI). The iC-GPC Assay is performed directly on positive blood cultures, confirmed by Gram stain to contain gram positive cocci. Cultures demonstrating mixed Gram stain results should not be tested with the assay. The iC-GPC Assay is validated for use with select BACTEC, BacTIALERT and VersaTREK blood culture bottles. The iC-GPC Assay is indicated for use in conjunction with other clinical and laboratory findings, such as blood culture isolate identification and antimicrobial susceptibility testing, to aid in the diagnosis of bacterial bloodstream infections; however, it is not used to monitor bloodstream infections.
The iC-GPC Assay detects organism DNA and identifies the following bacterial species and resistance markers:
Bacterial Species Staphylococcus aureus Staphylococcus epidermidis Streptococcus pneumoniae Enterococcus faecalis Enterococcus faecium
Resistance Markers
mecA- associated with methicillin resistance vanA- associated with vancomycin resistance vanB- associated with vancomycin resistance
The iC-GPC Assay detects the mecA resistance marker, inferring mecA-mediated methicillin resistance, and the vanA and vanB resistance markers, inferring vanAlvanB-mediated vancomycin resistance. In mixed growth, the iC-GPC Assay does not specifically attribute van-mediated vancomycin resistance to either E. faecalis or E. faecium, or mecA-mediated methicillin resistance to either S. aureus or S. epidermidis.
Sub-culturing of positive blood cultures is necessary to recover organisms for susceptibility testing. identification of organisms not detected by the iC-GPC Assay, differentiation of mixed growth, association of antimicrobial resistance marker genes to a specific organism, or for epidemiological typing.
The iC-GPC Assay utilizes polymerase chain reaction (PCR) for the amplification of specific targets and detects the amplified target DNA with fluorescence-based microarray hybridization. The iC-GPC Assay uses proprietary ARM-PCR (Amplicon Rescued Multiplex PCR) technology allowing for multiple targets to be amplified in one reaction. Targets are detected directly from patient positive blood cultures, confirmed by Gram stain to contain gram positive cocci. Testing is performed within a closed, disposable cassette that contains all the reagents required to complete the iC-GPC Assay, including a universal microarray.
To operate, the user opens the iC-GPC Cassette cap and pipettes an aliquot of the positive blood culture sample into the sample well of the cassette is then inserted into the iC-Processor, which performs the processes of DNA extraction, multiplex amplification, and microarray After processing is complete, the cassette is inserted into the iC-Reader for hybridization. fluorescence-based detection and data analysis. Final results are generated by iC-Report, computer software for data acquisition, analysis, and display.
Extraction, amplification, and hybridization are defined by an assay script controlled by the iC-Processor. The processing script is defined within a barcode label positioned on the top of each iC-GPC Cassette which communicates with the iC-Processor. To access and pierce the foil-sealed reagent wells located in the bottom well plate of the cassette, the processor manipulates the cassette to move the internal pipette horizontally and vertically. The script directs the transfer of reagents between the wells in the bottom well plate and finally to the array within the cassette. The iC-Processor is capable of processing 4 iC-Cassettes with random access.
Once processing is complete, the cassette is manually transferred from the iC-Processor to the iC-Reader where the microarray within the cassette is read. The iC-Reader is capable of reading up to 4 iC-Cassettes at one time. The results are interpreted via the iC-Report software and displayed for the user on an iMac computer. Raw data and result interpretations are stored within the iMac; raw data is accessible to authorized personnel only and is not available to the end user.
The provided document describes the iC-GPC Assay for use on the iC-System, a qualitative, multiplexed, in vitro diagnostic test for the detection and identification of potentially pathogenic gram-positive bacteria and resistance markers from positive blood cultures. The document details the performance studies conducted to support its substantial equivalence to a legally marketed predicate device (VERIGENE® Gram Positive Blood Culture Nucleic Acid Test (BC-GP)) and its overall analytical and clinical performance.
Here's an breakdown of the acceptance criteria and the studies proving the device meets them:
1. Table of Acceptance Criteria and Reported Device Performance
The document doesn't explicitly state "acceptance criteria" in a single, consolidated table with pre-defined thresholds. Instead, it presents performance metrics in various tests (reproducibility, LoD, inclusivity, exclusivity, method comparison). Acceptance for these tests is implied by the successful outcomes. The core performance is summarized in the method comparison study against an FDA-cleared multiplex assay and against traditional culture and susceptibility methods.
Below, I've compiled a table summarizing the key performance metrics from the Method Comparison section, which represents the device's main performance claim for its intended use. The "Acceptance Criteria" here are implicitly High agreement (e.g., >95%) for both positive and negative agreement, as is common for in vitro diagnostics devices aiming for substantial equivalence.
| Acceptance Criteria (Implied) | Reported iC-GPC Assay Performance (vs. FDA-Cleared Multiplex Assay) | Reported iC-GPC Assay Performance (vs. Culture & Biochemicals/AST) |
|---|---|---|
| Staphylococcus aureus (nuc) | ||
| High Positive Agreement | 97.0% (258/266) [94.2-98.5%] | 95.9% (259/270) [92.9-97.7%] |
| High Negative Agreement | 99.7% (645/647) [98.9-99.9%] | 99.8% (610/611) [99.1-100%] |
| Staphylococcus epidermidis (gseA) | ||
| High Positive Agreement | 98.3% (231/235) [95.7-99.3%] | 96.0% (216/225) [92.6-97.9%] |
| High Negative Agreement | 97.9% (664/678) [96.6-98.8%] | 96.5% (633/656) [94.8-97.7%] |
| Streptococcus pneumoniae (lytA) | ||
| High Positive Agreement | 85.2% (23/27) [67.5-94.1%] (Fresh: 82.6%) | 100% (21/21) [84.5-100%] |
| High Negative Agreement | 99.9% (885/886) [99.4-100%] | 99.8% (866/868) [99.2-99.9%] |
| Enterococcus faecalis (ddl) | ||
| High Positive Agreement | 96.7% (59/61) [88.8-99.1%] | 96.8% (60/62) [89.0-99.1%] |
| High Negative Agreement | 99.9% (851/852) [99.3-100%] | 99.9% (828/829) [99.3-100%] |
| Enterococcus faecium (fcm) | ||
| High Positive Agreement | 96.6% (28/29) [82.8-99.4%] | 96.6% (28/29) [82.8-99.4%] |
| High Negative Agreement | 99.8% (882/884) [99.2-99.9%] | 99.7% (859/862) [99.0-99.9%] |
| mecA (methicillin resistance) | ||
| High Positive Agreement | 96.1% (274/285) [93.2-97.8%] | 90.2% (257/285) [86.2-93.1%] |
| High Negative Agreement | 98.2% (617/628) [96.9-99.0%] | 97.0% (551/568) [95.3-98.1%] |
| vanA (vancomycin resistance) | ||
| High Positive Agreement | 95.0% (19/20) [76.4-99.1%] | 88.0% (22/25) [70.0-95.8%] (vanA/B combined) |
| High Negative Agreement | 99.4% (888/893) [98.7-99.8%] | 99.8% (861/863) [99.2-99.9%] (vanA/B combined) |
| vanB (vancomycin resistance) | ||
| High Positive Agreement | 100% (2/2) [34.2-100%] | 88.0% (22/25) [70.0-95.8%] (vanA/B combined) |
| High Negative Agreement | 99.9% (876/877) [99.4-100%] | 99.8% (861/863) [99.2-99.9%] (vanA/B combined) |
2. Sample Size and Data Provenance
- Test Set Sample Size:
- Clinical Method Comparison Study: 966 positive blood culture specimens initially enrolled, reduced to 913 (879 fresh prospective, 34 frozen prospective) after withdrawals.
- Contrived Samples: An additional 168 contrived samples.
- Data Provenance: The general text of the letter indicates "four geographically dispersed clinical sites." Given the context of a US regulatory submission to the FDA, it is highly likely these sites were in the United States. The "Expected Values" table further specifies "U.S. State" data from NY, WI, NM, and FL. The study collected prospective (fresh and frozen) and contrived samples.
3. Number of Experts and Qualifications for Ground Truth
The document does not explicitly state the "number of experts" or their "qualifications" for establishing the ground truth for the clinical method comparison test set.
However, for the comparison methods that served as ground truth:
- FDA-cleared multiplex assay: This is a pre-existing, validated device, implying its results are considered reliable.
- Conventional reference methods: This includes "subculture, identification of isolates using biochemical methods or MALDI-TOF, and phenotypic antimicrobial susceptibility testing (AST)." These methods are standard clinical laboratory practices performed by trained microbiologists and clinical laboratory scientists. The qualification of these individuals would adhere to standard laboratory accreditation and personnel requirements.
4. Adjudication Method for the Test Set
The document details discordant analysis for the method comparison studies:
- Against FDA-Cleared Multiplex Assay: PCR and bidirectional sequencing were performed for all specimens with positive results for resistance markers by either the iC-GPC Assay or the FDA-cleared multiplex assay. These results were used to analyze and investigate discordant results. This implies a form of 2+1 adjudication or investigation where if the iC-GPC and comparator disagreed, an independent gold standard (PCR/sequencing) was used to resolve.
- Against Conventional Reference Methods: PCR and bi-directional sequencing were not used for discordant analysis between iC-GPC and conventional reference method results. This suggests that the conventional methods served as the direct reference, without further independent adjudication for discrepancies with the iC-GPC assay.
5. Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study
This is not a multi-reader multi-case (MRMC) study. The iC-GPC Assay is an in vitro diagnostic device for laboratory use that provides automated results, not a diagnostic imaging AI algorithm that assists human readers. Therefore, there is no human-in-the-loop performance measurement or effect size reported here regarding human reader improvement with AI assistance.
6. Standalone (Algorithm Only Without Human-in-the-Loop Performance) Study
Yes, this entire submission revolves around the standalone performance of the iC-GPC Assay, which is an automated system (iC-System) that performs DNA extraction, multiplex amplification, hybridization, and detection to generate results. The reported performance metrics (positive/negative agreement, LoD, inclusivity, exclusivity) are a direct measure of the algorithm's (device's) performance.
7. Type of Ground Truth Used
- For Analytical Studies (LoD, Inclusivity, Exclusivity, Reproducibility, etc.): Ground truth was established by known concentrations/strains of organisms, obtained from characterized sources (e.g., ATCC strains, well-characterized clinical isolates) and confirmed by methods such as colony counts.
- For Clinical Method Comparison Study:
- Primary Ground Truth 1: An FDA-cleared multiplex assay.
- Secondary Ground Truth 2: Conventional laboratory reference methods (subculture, biochemical identification, MALDI-TOF, and phenotypic antimicrobial susceptibility testing (AST)).
- Discordant Resolution (for resistance markers in comparison to FDA-Cleared Multiplex Assay): PCR and bi-directional sequencing as an independent, highly accurate molecular method.
8. Sample Size for the Training Set
The document does not provide information on the training set size for the iC-GPC Assay's development. This FDA 510(k) submission focuses on the validation of the device through performance studies (test sets) rather than detailing the specifics of its development or "training" phase. For in vitro diagnostics that use molecular techniques, the "training" analogous to machine learning models usually involves extensive research and development to optimize primer and probe design, reaction conditions, and analytical algorithms based on large collections of known positive and negative samples, but these are typically internal R&D activities not explicitly reported as "training set size" in the final validation summary.
9. How the Ground Truth for the Training Set Was Established
As the document does not detail a "training set," it also does not describe how its ground truth was established. However, for a molecular diagnostic assay like this, the underlying "ground truth" for developing and optimizing the assay's targets and reaction conditions would typically be established through:
- Known, characterized bacterial strains and clinical isolates: Identified and confirmed using a combination of standard microbiological methods (culture, Gram stain, biochemical tests, phenotypic susceptibility testing) and advanced molecular methods (16S rRNA gene sequencing, whole-genome sequencing) to determine precise species and resistance marker presence.
- Synthetic DNA/RNA targets: Used for initial assay design and analytical performance testing.
- Bioinformatics analysis: To select highly specific gene targets (like gseA, nuc, lytA, ddl, fcm, mecA, vanA, vanB) that are unique to the target organisms and resistance mechanisms.
This developmental phase would involve rigorous, iterative testing and refinement against a comprehensive panel of both target and non-target organisms to ensure high sensitivity and specificity before formal validation studies like those presented in the 510(k) summary are conducted.
§ 866.3365 Multiplex nucleic acid assay for identification of microorganisms and resistance markers from positive blood cultures.
(a)
Identification. A multiplex nucleic acid assay for identification of microorganisms and resistance markers from positive blood cultures is a qualitative in vitro device intended to simultaneously detect and identify microorganism nucleic acids from blood cultures that test positive by Gram stain or other microbiological stains. The device detects specific nucleic acid sequences for microorganism identification as well as for antimicrobial resistance. This device aids in the diagnosis of bloodstream infections when used in conjunction with other clinical and laboratory findings. However, the device does not replace traditional methods for culture and susceptibility testing.(b)
Classification. Class II (special controls). The special control for this device is FDA's guideline document entitled “Class II Special Controls Guideline: Multiplex Nucleic Acid Assay for Identification of Microorganisms and Resistance Markers from Positive Blood Cultures.” For availability of the guideline document, see § 866.1(e).