(25 days)
The FilmArray Blood Culture Identification (BCID) Panel is a qualitative multiplexed nucleic acid-based in vitro diagnostic test intended for use with FilmArray BCID Panel is capable of simultaneous detection and identification of multiple bacterial and yeast nucleic acids and select genetic determinants of antimicrobial resistance. The BCID assay is performed directly on blood culture samples identified as positive by a continuous monitoring blood culture system that demonstrate the presence of organisms as determined by Gram stain.
The following gram-positive bacteria, gram-negative bacteria, and yeast are identified using the FilmArray BCD Panel: Enterococci, Listeria monocytogenes, Staphylococci (including specific differentiation of Staphylococcus aureus), Streptococci (with specific differentiation of Streptococcus agalactiae, Streptococcus pneumoniae, and Streptococcus pyogenes), Acinetobacter baumannii, Enterobacteriaceae (including specific differentiation of the Enterchacter cloacae complex, Escherichia coli, Klebsiella oxytoca, Klebsiella pneumoniae, Proteus, and Serratia marcescens), Haemophilus influenzae, Neisseria meningitidis (encapsulated), Pseudomonas aeruginosa, Candida glabrata, Candida krusei, Candida parapsilosis, and Candida tropicalis.
The FilmArray BCID Panel also contains assays for the determinants of resistance to methicillin (mecA), vancomycin (vanA and vanB), and carbapenems (blaKPC) to aid in the identification of potentially antimicrobial resistant organisms in positive blood culture samples. The antimicrobial resistance gene detected may or may not be associated with the agent responsible for disease. Negative results for these select antimicrobial resistance gene assays do not indicate susceptibility, as multiple mechanisms of resistance to methicillin, vancomycin, and carbapenens exist. FilmArray BCID is indicated as an aid in the diagnosis of bacteremia and fungemia and results should be used in conjunction with other clinical and laboratory findings. Positive FilmArray results do not rule out co-infection with organisms not included in the FilmArray BCID Panel. FilmArray BCID is not intended to monitor treatment for bacteremia or fungemia.
Subculturing of positive blood cultures is necessary to recover organisms for susceptibility testing and epidemiological typing, to identify organisms in the blood culture that are not detected by the FilmArray BCID Panel, and for species determination of some Staphylococci, Streptococci, Streptococci, and Enterobacteriaceae that are not specifically identified by the FilmArray BCID Panel assays.
The FilmArray Blood Culture Identification (BCID) Panel is a multiplex nucleic acid test designed to be used with a FilmArray system. The FilmArray BCID pouch contains freeze-dried reagents to perform nucleic acid purification and nested, multiplex PCR with DNA melt analysis. The FilmArray Blood Culture Identification (BCID) Panel simultaneously tests a single positive blood culture sample to provide results for 24 different organisms and organism groups that cause bloodstream infections and three genetic markers that are known to confer antimicrobial resistance (see Table 1).
A test is initiated by loading Hydration Solution and a positive blood culture sample mixed with the provided Sample Buffer into the FilmArray BCID pouch. The pouch contains all of the reagents required for specimen testing and analysis in a freeze-dried format; the addition of Hydration Solution and sample Buffer Mix rehydrates the reagents. After the pouch is prepared, the software guides the user though the steps of placing the pouch into the instrument. scanning the pouch barcode, entering the sample identification, and initiating the run.
The FilmArray instrument contains a coordinated system of inflatable bladders and seal points, which act on the pouch to control the movement of liquid between the pouch blisters. When a bladder is inflated over a reagent blister, it forces liquid from the blister into connecting channels. Alternatively, when a seal is placed over a connecting channel it acts as a valve to open or close a channel. In addition, electronically controlled pneumatic pistons are positioned over multiple plungers in order to deliver the rehydrated reagents into the blisters at the appropriate times. Two Peltier devices control heating and cooling of the pouch to drive the PCR reactions and the melt curve analysis.
Nucleic acid extraction occurs within the FilmArray pouch using mechanical lysis and standard magnetic bead technology. After extracting and purifying nucleic acids from the unprocessed sample, a nested multiplex PCR is executed in two stages. During the first stage, a single, large volume, highly multiplexed PCR reaction which includes all primers of the outer primer sets, is performed. The products from first stage PCR are then diluted and combined with a fresh, primer-free master mix and a fluorescent double stranded DNA binding dye (LC Green® Plus, BioFire Defense, LLC). The solution is then distributed to each well of the array. Array wells contain sets of primers designed specifically to amplify sequences internal to the PCR products generated during the first stage PCR reaction. The 2nd stage PCR, or nested PCR, is performed in singleplex fashion in each well of the array. At the conclusion of the 2nd stage PCR, the array is interrogated by melt curve analysis for the detection of signature amplicons denoting the presence of specific targets. A digital camera placed in front of the array captures fluorescent images of the PCR reactions and software interprets the data.
The FilmArray software automatically interprets the results of each DNA melt curve analysis and combines the data with the results of the internal pouch controls to provide a test result for each organism on the panel.
Here's a breakdown of the acceptance criteria and study information for the FilmArray Blood Culture Identification (BCID) Panel for use with FilmArray Torch, based on the provided document:
Acceptance Criteria and Device Performance
The document doesn't explicitly state numerical acceptance criteria in a dedicated section with thresholds. However, it describes the performance goal and the reported device performance as follows:
| Acceptance Criteria / Performance Goal | Reported Device Performance |
|---|---|
| Reproducible detection of each FilmArray BCID analyte (including antibiotic resistance markers) at concentrations consistent with levels in positive blood culture bottles at initial positivity. | Reproducible detection was confirmed for each FilmArray BCID analyte. 100% of samples tested on FilmArray Torch systems yielded the expected "Detected" results. |
| Agreement with expected negative results ("Not Detected") for each analyte. | Agreement with the expected negative results (Not Detected) was >98% for each analyte. |
| Substantial equivalence in performance characteristics (including reproducibility) to the predicate device (FilmArray BCID Panel on FilmArray and FilmArray 2.0 systems). | "Non-clinical validation studies have established that the performance characteristics of FilmArray BCID, including reproducibility, are substantially equivalent on FilmArray, FilmArray 2.0, and FilmArray Torch." (This is a qualitative statement of equivalence based on the quantitative results above). |
Study Information
2. Sample size used for the test set and the data provenance:
- Sample Size: 30 replicates per analyte per system for 90 total replicates per analyte. (The document doesn't specify how many analytes are on the panel, but Table 1 lists 24 organism targets and 4 resistance markers, implying a total of 28 analytes. So, for each of these 28 analytes, 90 samples were tested).
- Data Provenance: The study used "contrived samples" containing analytes at specific concentrations. This indicates a prospective, laboratory-controlled study, rather than retrospective clinical data. No country of origin is explicitly stated, but the submission is to the FDA (USA).
3. Number of experts used to establish the ground truth for the test set and the qualifications of those experts:
- This study evaluates an in vitro diagnostic (IVD) device that directly detects nucleic acids. The ground truth for the contrived samples would be established by the known composition and concentration of the analytes spiked into the samples during their preparation, not by human expert interpretation. Therefore, no external human experts were involved in establishing the ground truth for this specific test set.
4. Adjudication method (e.g. 2+1, 3+1, none) for the test set:
- Not applicable. As this is an IVD device testing contrived samples against known concentrations, there is no need for expert adjudication. The result is either "Detected" or "Not Detected" compared to the known content of the contrived sample.
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:
- No, a multi-reader multi-case (MRMC) comparative effectiveness study was not done. This device is an automated IVD and does not involve human readers interpreting results in the same way an AI for image analysis would. Its output is an automated interpretation of molecular detection.
6. If a standalone (i.e. algorithm only without human-in-the loop performance) was done:
- Yes, this was effectively a standalone performance evaluation of the FilmArray Torch system running the BCID Panel. The "algorithm" (the automated processes and software interpretation within the FilmArray system) directly processed the samples and generated results without human interpretation of raw data; the user only sees automated test interpretation and report generation.
7. The type of ground truth used (expert consensus, pathology, outcomes data, etc.):
- For the test set, the ground truth was known composition and/or spiking of analytes (nucleic acids) at specific concentrations in the contrived samples.
8. The sample size for the training set:
- The document describes a submission for a modified device (FilmArray Torch) to be used with an existing reagent panel (FilmArray BCID Panel). It states "There have been no changes to the previously cleared FilmArray BCID Panel reagent kit itself." Therefore, the training of the assay (the BCID Panel's detection algorithms) would have occurred during the development and clearance of the original K143171 predicate device. This document does not provide details on the training set for that original assay, as the focus here is on the new instrument's equivalence. The study described (using 90 replicates per analyte) is a validation/test set, not a training set.
9. How the ground truth for the training set was established:
- As noted above, details about the training set for the original BCID Panel assay are not provided in this document. For molecular diagnostic assays like this, training data would typically involve:
- Known positive samples: Samples containing confirmed target organisms/genes (e.g., pure cultures, reference materials).
- Known negative samples: Samples confirmed to lack the target organisms/genes.
- Specificity panels: Samples containing closely related organisms or common co-infecting agents to ensure accurate differentiation and minimize cross-reactivity.
- The ground truth would be established through gold standard microbiology methods (e.g., culture, sequencing, validated reference PCRs) for organisms, and often sequencing or known genetic constructs for resistance genes.
§ 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).