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The BinaxNOW® Influenza A & B Test is an in vitro immunochromatographic assay for the qualitative detection of influenza A and B nucleoprotein antigens in nasopharyngeal (NP) swab, nasal swab, and nasal wash/aspirate specimens. It is intended to aid in the rapid differential diagnosis of influenza A and B viral infections. Negative results do not preclude influenza virus infection and should not be used as the sole basis for treatment or other management decision.

The BinaxNOW® Influenza A & B Test is an immunochromatographic membrane assay that uses highly sensitive monoclonal antibodies to detect influenza type A & B nucleoprotein antigens in respiratory specimens. These antibodies and a control antibody are immobilized onto a membrane support as three distinct lines and combined with other reagents/pads to construct a test strip. This test strip is mounted inside a cardboard, book-shaped hinged test device. Swab specimens require a sample preparation step, in which the sample is eluted off the swab into elution solution, saline, or transport media. Nasal wash/aspirate samples require no preparation. Sample is added to the top of the test strip and the test device is closed. Test results are interpreted at 15 minutes based on the presence or absence of pink-to-purple colored Sample Lines. The blue Control Line turns pink in a valid assay.

Here's a breakdown of the acceptance criteria and study details for the BinaxNOW® Influenza A & B Test, based on the provided 510(k) summary:

1. Table of Acceptance Criteria and Reported Device Performance

The acceptance criteria for sensitivity and specificity are not explicitly stated as pre-defined targets within the provided text. Instead, the document presents the observed performance of the device against the reference method (cell culture/DFA) in various clinical studies. The substantial equivalence is established by comparing this observed performance to the predicate device, the BD Directigen™ Flu A+B Test (though detailed performance for the predicate is not provided in this summary).

For the purpose of this analysis, we will present the reported device performance from the prospective and retrospective clinical studies.

BinaxNOW® Influenza A & B Test Performance vs. Cell Culture/DFA (Prospective Study)

BinaxNOW® Influenza A & B Test Performance vs. Cell Culture/DFA (Retrospective Study)

Analytical Sensitivity (Limit of Detection - LOD)

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

• Prospective Study Test Set:

  • Total Specimens: 846
  • Provenance: Multi-center, "central testing laboratory outside the US during the 2004 respiratory season and at three US trial sites during the 2005-2006 respiratory season." Data is prospective.
  • Patient demographics: 44% male, 54% female, 54% pediatric (<18 years), 46% adult (≥18 years).
  • Sample types: Nasopharyngeal (NP) swabs, nasal swabs.

• Retrospective Study Test Set:

  • Total Specimens: 293
  • Provenance: Collected from symptomatic patients at multiple physician offices, clinics, and hospitals in the Southern, Northeastern, and Midwestern regions of the United States, and from one hospital in Sweden. Data is retrospective (frozen clinical samples).
  • Patient demographics: 53% male, 47% female, 62% pediatric (<18 years), 38% adult (≥18 years).
  • Sample types: Nasal wash/aspirate (61%), NP swabs (39%).

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

The document does not explicitly state the number or qualifications of experts used to establish the ground truth. It refers to "Cell Culture / DFA" as the reference method. In a typical clinical setting, cell culture and Direct Fluorescent Antibody (DFA) testing would be performed and interpreted by trained laboratory professionals, such as medical technologists or microbiologists. Specific expert qualifications (e.g., years of experience, board certification) are not provided.

4. Adjudication Method for the Test Set

The document does not describe an adjudication method for disagreements or indeterminate results between different readers or between the device and the ground truth. The "ground truth" (Cell Culture/DFA) is treated as the definitive reference.

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 MRMC comparative effectiveness study is mentioned, as this device is a rapid diagnostic test (immunochromatographic assay) and not an AI-assisted diagnostic tool that would typically involve human readers interpreting images. The closest mention of human involvement in interpretation is in the analytical sensitivity study, where "Twelve (12) different operators each interpreted 2 devices run at each concentration," which is an operator variability assessment, not an MRMC study for diagnostic improvement.

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

This device is an in vitro diagnostic test, meaning its performance is inherently standalone in the sense that the test itself (reagents, membrane, etc.) produces the result. Human interpretation is required to read the pink-to-purple colored Sample Lines and the blue Control Line. However, there is no "algorithm" in the modern AI sense described. The "standalone" performance here refers to the device's ability to detect antigens in specimens without comparison to human interpretation of the same device output; rather, its output is compared to a gold standard (cell culture). The clinical study data presented (sensitivity and specificity) can be considered the standalone performance of the device as interpreted by an operator.

7. The Type of Ground Truth Used

The type of ground truth used is Cell Culture / DFA (Direct Fluorescent Antibody testing). This is a common and accepted laboratory reference method for influenza virus detection.

8. The Sample Size for the Training Set

The document does not explicitly mention a "training set" in the context of device development or algorithm training. Since this is an immunochromatographic assay and not an AI/ML-based device, there isn't a traditional "training set" as understood in machine learning. The clinical and analytical studies serve to validate the device's performance against established methods.

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

As there is no traditional "training set" for an AI/ML algorithm, this question is not directly applicable. The "ground truth" for the performance evaluation (test sets) was established using Cell Culture/DFA, which are established laboratory techniques performed by trained personnel.

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