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The IMDx Flu A/B and RSV for Abbott m2000 assay performed on the Abbott m2000 System is a qualitative in vitro diagnostic test designed for the detection of influenza B, and RSV RNA directly from nasopharyngeal swabs from patients with signs and symptoms of respiratory infection. The assay detects RNA from influenza A. influenza B, and RSV (A and B) using real-time, reverse transcription polymerase chain reaction (rRT-PCR) and fluorogenic target specific hybridization for unique sequences in the viral target genomes. The IMDx Flu A/B and RSV for Abbott m2000 assay is intended for use as an aid in diagnosing influenza A and/or RSV infection.

Negative results for influenza B, or RSV do not preclude influenza virus or RSV infection and should not be used as the sole basis for diagnosis, treatment, or patient management decisions. Conversely, positive results do not rule-out bacterial infection or co-infection with other viruses. The agent(s) detected may not be the definite cause of disease. The use of additional laboratory testing and clinical presentation must be considered when diagnosing respiratory viral infection.

Performance characteristics for influenza A were established during the 2011-2013 influenza seasons when Influenza A/2009 H1N1 and Influenza A/H3 were the predominant influenza A viruses in circulation. When other influenza A viruses are emerging, performance characteristics may vary,

If infection with a novel influenza A virus is suspected based on current clinical and epidemiological screening criteria recommended by public health authorities, specimens should be collected with appropriate infection control precautions for novel virulent influenza viruses and sent to state or local health department for testing. Viral culture should not be attempted in these cases unless a BSL 3+ facility is available to receive and culture specimens.

The IMDx Flu A/B and RSV for Abbott m2000 assay uses nucleic acid extraction and purification technology, performed on the Abbott m2000sp. combined with rRT-PCR. performed with the Abbott m2000rt, to generate and detect amplified products from influenza A, influenza B, and RSV RNA that is isolated from clinical specimens.

The assay targets the influenza A matrix (M) gene, influenza B non-structural protein (NS1) gene, and RSV A and RSV B fusion (F) gene. The presence of a viral RNA target sequence is indicated by the fluorescent signal generated through the use of fluorescently labeled oligonucleotide probes on the Abbott m2000rt instrument. The probes do not generate a signal unless they are specifically bound to the amplification cycle at which fluorescent signal is detected by the Abbott m2000rt is inversely proportional to the viral RNA target concentration present in the original sample.

An RNA bacteriophage species unrelated to influenza B, or RSV is introduced into each specimen during sample preparation to serve as a process control bacteriophage is lysed simultaneously with influenza A, influenza B and RSV B in the sample, and amplified in the same reaction as the viral RNA targets using rRT-PCR. The process control serves to demonstrate that the entire assay process has proceeded correctly for each sample.

Here's a breakdown of the acceptance criteria and the study details for the IMDx Flu A/B and RSV for Abbott m2000 assay:

1. Table of Acceptance Criteria and Reported Device Performance

The acceptance criteria for diagnostic devices often involve achieving a certain level of sensitivity and specificity against a defined ground truth. Based on the provided summary, the FDA cleared the device, implying that the observed performance met the agency's criteria. While explicit "acceptance criteria" are not listed as target percentages, the "Clinical Agreement Summary" tables present the device's performance metrics.

2. Sample Size Used for the Test Set and Data Provenance

• Test Set Sample Size: A total of 932 nasopharyngeal swab (NPS) samples were tested and analyzed for performance across two influenza seasons (2011-2012 and 2012-2013).
• Data Provenance: The samples were prospectively collected from four (2011-2012 season) and three (2012-2013 season) geographically diverse test sites within the United States. These were nasopharyngeal swabs collected for routine influenza testing. The study period was February-April 2012 and March-April 2013.

3. Number of Experts Used to Establish the Ground Truth for the Test Set and Qualifications

The document does not specify the number of experts or their qualifications for establishing the ground truth. It states that the performance was assessed "compared to viral culture followed by direct fluorescent antibody (DFA) detection." This implies laboratory techniques were used as the reference standard, rather than expert clinical consensus or interpretation of images by experts.

4. Adjudication Method for the Test Set

The document mentions that "Discordant samples were tested using the Nanosphere Verigene® Respiratory Virus Plus Nucleic Acid Test (RV+) on the Verigene® System and subsequent results are documented in the footnote." This indicates that discordant results (where the IMDx assay result did not match the initial ground truth) were adjudicated using a "third-party" FDA-cleared molecular assay (the predicate device).

5. Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study

• No, an MRMC comparative effectiveness study was not conducted. This device is an in vitro diagnostic test for detecting viral RNA, not an imaging device or a tool that directly assists human readers in interpreting clinical information.

6. Standalone (Algorithm Only) Performance Study

• Yes, a standalone performance study was done. The entire study described under "Clinical Agreement" and "Analytical Performance" evaluates the algorithm's performance in detecting viral RNA without human interpretation or intervention in the diagnostic process beyond running the assay. The results presented are exclusively for the device's analytical detection capabilities.

7. Type of Ground Truth Used

• Clinical Agreement: The primary ground truth for the clinical agreement study was viral culture followed by direct fluorescent antibody (DFA) detection. For discordant samples, a FDA cleared molecular assay (Nanosphere Verigene® Respiratory Virus Plus Nucleic Acid Test) was used for adjudication.
• Analytical Performance: For analytical studies (reproducibility, analytical sensitivity, reactivity, specificity, interference), the ground truth generally refers to precisely prepared "spiked" samples with known concentrations of viral strains or challenging substances.

8. Sample Size for the Training Set

The document does not provide information regarding the sample size for a training set. This is typical for FDA 510(k) summaries for IVD assays. The development and training of such assays often involve proprietary internal validation data not typically released in a 510(k) summary, which focuses on clinical validation for market clearance.

9. How the Ground Truth for the Training Set Was Established

As with the training set sample size, the document does not provide information on how the ground truth for any potential training set was established. This information is typically considered proprietary to the manufacturer's development process and not part of the public 510(k) summary.

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The IMDx VanR for Abbott m2000 assay is an in vitro diagnostic assay that uses polymerase chain reaction (PCR) amplification for the qualitative detection of nucleic acids encoding the vancomycin resistance genes vanA and/or vanB. The assay is performed directly on human perirectal swabs, rectal swabs, or stool specimens from patients at risk for Vancomycin Resistant Enterococcus (VRE) colonization. The IMDx VanR for Abbott m2000 assay detects the presence of vanA and vanB genes that can be associated with vancomycin-resistant enterococci. The IMDx VanR for Abbott m2000 assay can be used as an aid to identify. prevent and control vancomycin-resistant colonization in healthcare settings. The IMDx VanR for Abbott m2000 assay is not intended to diagnose VRE infection nor to guide or monitor treatment of infection. Culture methods are necessary to recover organisms for epidemiology typing and confirmation testing.

The IMDx VanR for Abbott m2000 assay is a PCR-based assay that targets regions unique to the vanA and vanB vancomycin resistance genes that may be associated with vancomycin resistant Enterococcus (VRE). Detection of the vanA and vanB genes is measured by the presence of fluorescently-labeled oligonucleotide probes that generate a fluorescent signal when specifically bound to amplified vanA and/or vanB PCR products. Differentiation of vanA from vanB is attained by labeling the oligonucleotide probes with different colored fluorescent dyes. The amplification cycle at which fluorescent signal is detected by the Abbott m2000rt is inversely proportional to the vanA and vanB DNA target level present in the sample.

The IMDx VanR for Abbott m2000 assay includes reagents for the detection of the assay process control, which contains inactivated bacteria, unrelated to enterococci, and is introduced into each specimen during sample preparation. The process control (also acting as an internal control (IC)) is co-extracted with the specimen and co-amplified in the same PCR reaction as the vanA and vanB targets. The IC demonstrates that the entire assay process has proceeded within specification.

Here's an analysis of the provided information, focusing on the acceptance criteria and the study proving the device meets them:

Acceptance Criteria and Device Performance for IMDx VanR for Abbott m2000

The document provided, K123753, describes the IMDx VanR for Abbott m2000 assay, an in vitro diagnostic device for detecting vancomycin resistance genes. The acceptance criteria are implicitly derived from the performance goals demonstrated in the clinical studies, as explicit pre-defined acceptance criteria are not directly stated in the summary. The performance is reported as sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) based on comparison to a "gold standard" method.

1. Table of Acceptance Criteria and Reported Device Performance

Note on Acceptance Criteria: The document does not explicitly state numerical acceptance criteria (e.g., "Sensitivity must be >X%"). Instead, the clinical performance study aims to demonstrate that the device performs comparably and effectively for its intended use, implying that the reported percentages of sensitivity, specificity, PPV, and NPV are deemed acceptable for supporting substantial equivalence to the predicate device.

2. Sample Size Used for the Test Set and Data Provenance

• Test Set (Clinical Performance Study):
  • Peri-rectal swabs: 587 samples
  • Rectal swabs: 444 samples (further broken down into prospective and retrospective collections)
    • Prospective: 400 samples
    • Retrospective: 44 samples
  • Stool specimens: 469 samples
  • Total Clinical Samples: 587 + 444 + 469 = 1500 samples
• Data Provenance: Samples were collected from "five geographically diverse test sites within the United States." The study included both prospective and retrospective collection for rectal swabs.

3. Number of Experts Used to Establish the Ground Truth for the Test Set and Qualifications of those Experts

The document does not specify the number or qualifications of experts used to establish the ground truth. It states that the ground truth was "enriched culture combined with confirmation of the molecular basis of vancomycin resistance of isolates using an alternate PCR method." This implies laboratory personnel with expertise in microbiology and molecular diagnostics, but no specific number or detailed qualifications are provided.

4. Adjudication Method for the Test Set

The document does not describe a formal adjudication method (e.g., 2+1, 3+1, none) for the test set. The ground truth was established by a combination of enriched culture and an alternate PCR method, implying a direct comparison against these established laboratory techniques rather than a human consensus process.

5. If a Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study Was Done

No, an MRMC comparative effectiveness study was not done. This study focuses on the in vitro diagnostic performance of the assay itself (device vs. reference method) rather than evaluating human reader performance with and without AI assistance.

6. If a Standalone (i.e., algorithm only without human-in-the-loop performance) Was Done

Yes, the clinical performance study evaluates the IMDx VanR for Abbott m2000 assay in a standalone manner. The assay is an automated PCR-based diagnostic test, and its results are compared directly to the ground truth (enriched culture + alternative PCR). There is no human interpretation of images or other data being assisted by the algorithm; the assay itself generates the result.

7. The Type of Ground Truth Used

The ground truth used was a combination of enriched culture combined with confirmation of the molecular basis of vancomycin resistance of isolates using an alternate PCR method. This is a highly robust ground truth for detecting the presence of vanA and/or vanB genes and is considered a reference standard in microbiology.

8. The Sample Size for the Training Set

The document does not explicitly state the sample size for a "training set." This type of molecular diagnostic assay typically undergoes extensive analytical validation (e.g., LOD, reactivity, cross-reactivity) using characterized strains and spiked samples, and then its clinical performance is evaluated on a distinct clinical test set. It's possible that data from these extensive analytical studies could be considered analogous to training data for method optimization, but a defined "training set" in the context of machine learning is not applicable here as it's a rule-based PCR assay, not an AI/ML algorithm.

9. How the Ground Truth for the Training Set Was Established

As noted above, a traditional "training set" as understood in AI/ML is not described. However, for the analytical studies (e.g., Analytical Reactivity, Challenge Study), the ground truth was established using "well-characterized vancomycin-resistant Enterococcus strains and/or clinical isolates" and other organisms. These strains would have their vanA/vanB status, and other genetic characteristics, confirmed through standard microbiological and molecular methods (e.g., sequencing, biochemical tests, established PCR assays).

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