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The Sofia Influenza A +B FIA employs immunofluorescence to detect influenza B viral nucleoprotein antigens in nasal swab, nasopharyngeal swab, and nasopharyngeal aspirate/wash in fresh or transport media specimens from symptomatic patients. This qualitative test is intended for use as an aid in the rapid differential diagnosis of acute influenza A and influenza B viral infections. The test is not intended to detect influenza C antigens. A negative test is presumptive and it is recommended these results be confirmed by virus culture or an FDA-cleared influenza A and B molecular assay. Negative results do not prectude influenza virus infections and should not be used as for treatment or other management decisions. The test is intended for professional and laboratory use.

Performance characteristics for influenza A and B were established during February through March 2011 when influenza viruses A/California 7/2009 (2009 H1N1), A/Perth/16/2009 (H3N2), and B/Brisbane/60/2008 (Victoria-Like) were the predominant influenza viruses in circulation according to the Mortality Weekly Report from the CDC entitled "Update: Influenza Activity-United States, 2010-2011 Season, and Composition of the 2011-2012 Influenza Vaccine". Performance characteristics may vary against other emerging influenza viruses.

If infection with a novel influenza 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. Virus culture should not be attempted in these cases unless a BSL 3+ facility is available to receive and culture specimens.

The Sofia Influenza A+B FIA employs immunofluorescence technology that is used with Sofia to detect influenza virus nucleoproteins. This test allows for the differential detection of influenza A and influenza B antigens.

The Sofia Influenza A+B FIA is a lateral-flow immunoassay that uses monoclonal antibodies that are specific for influenza antigens and have no known cross-reactivity to normal flora or other known respiratory pathogens.

Nasal swab, nasopharyngeal swab, and nasopharyngeal aspirate/wash specimens (both fresh and in VTM) are used for this test. The patient specimen is placed in the Reagent Tube, during which time the virus particles in the specimen are disrupted, exposing internal viral nucleoproteins. After disruption, the specimen is dispensed into the cassette sample well. From the sample well, the specimen migrates through a test strip containing various unique chemical environments. If influenza viral antigen is present, they will be trapped in a specific location.

Note: Depending upon the user's choice, the cassette is either placed inside Sofia for automatically timed development (Walk Away Mode) or placed on the counter or bench top for a manually timed development and then placed into Sofia to be scanned (Read Now Mode).

Sofia will scan the test strip and measure the fluorescent signal by processing the results using method-specific algorithms. Sofia will display the test results (Positive, or Invalid) on the screen. The results can also be automatically printed on an integrated printer if this option is selected.

The provided text describes the 510(k) summary for the Sofia® Influenza A+B FIA device. Here's an analysis of the acceptance criteria and the study that proves the device meets them, based on the provided information.

1. Table of Acceptance Criteria and Reported Device Performance

The document does not explicitly state pre-defined acceptance criteria in terms of specific performance metrics (e.g., minimum sensitivity or specificity targets). Instead, it presents performance data from a clinical study to demonstrate "substantial equivalence" to a predicate device and suitability for use with viral transport media (VTM).

Therefore, the "acceptance criteria" can be inferred to be a demonstration of substantial equivalence and acceptable performance, particularly when using VTM, compared to the predicate device which only used fresh specimens. The provided text, however, does not include a direct comparison table of the proposed device's performance against the predicate device's performance metrics for all relevant parameters (like sensitivity and specificity). It mainly focuses on the new capability (VTM use) and the overall conclusion of substantial equivalence.

Inferred "Acceptance Criteria" (Demonstrated Substantial Equivalence and Acceptable Performance with VTM)

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

• Test Set Sample Size: The document does not explicitly state the numerical sample size for the multi-center field clinical study. It only mentions that a "multi-center field clinical study was performed."
• Data Provenance: The study was a "multi-center field clinical study." While the specific countries are not mentioned, it's generally understood that such studies for FDA submissions typically include data from the United States, given the context of the FDA approval. The study collected data "during February through March 2011" making it retrospective in relation to the submission date of October 13, 2015.

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

The document does not provide details on the number or qualifications of experts used to establish the ground truth for the test set.

4. Adjudication Method for the Test Set

The document does not specify the adjudication method used for the test set.

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

An MRMC study was not done. The device, Sofia® Influenza A+B FIA, is an immunofluorescence assay read by an instrument (Sofia Analyzer), not a human visual interpretation. Therefore, the concept of human readers improving with or without AI assistance is not applicable to this device. The results are displayed by the instrument as "Positive, Negative, or Invalid."

6. If a Standalone (i.e. algorithm only without human-in-the-loop performance) was done

Yes, a standalone performance evaluation was done. The Sofia® Influenza A+B FIA is an automated system where the Sofia Analyzer scans the test strip and processes the results using "method-specific algorithms." The instrument then displays the results. This represents the algorithm's standalone performance.

7. The Type of Ground Truth Used

The ground truth for the clinical study is not explicitly stated in the provided text. However, for influenza diagnostic tests, the common "gold standards" or ground truths involve:

• Virus culture: This is mentioned in the "Indications for Use" as a recommended confirmation for negative test results ("confirmed by cell culture").
• FDA-cleared influenza A and B molecular assay: Also mentioned in the "Indications for Use" as a confirmation method.

Given the context, it is highly probable that a comparative method such as virus culture or an FDA-cleared molecular assay was used as the ground truth reference for the clinical performance study.

8. The Sample Size for the Training Set

The document does not mention a "training set" in the context of an algorithm or AI development. The device is a lateral-flow immunoassay with an instrument reader. The "method-specific algorithms" within the Sofia Analyzer would be preset and validated, rather than "trained" on a specific dataset in the way a machine learning model is trained. Therefore, there's no explicitly stated training set for an AI/algorithm in this document.

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

As there is no mention of a "training set" for an AI or algorithm in the conventional sense, the establishment of ground truth for such a set is not applicable or described in the provided information.

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