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Binax NOW Flu B Test is an in vitro rapid The immunochromatographic assay for the qualitative detection of influenza B nucleoprotein antigen in nasal wash and nasopharyngeal swab specimens from symptomatic patients. It is intended to aid in the rapid diagnosis of influenza B infections. Negative test results should be confirmed by cell culture.

The Binax NOW® Binax Flu B Test is an immunochromatographic membrane assay used to detect influenza B nucleoprotein antigen in nasal wash and nasopharyngeal sswab specimens. A test strip, containing goldconjugated and immobilized anti-influenza B antibodies, is mounted on the right side of a cardboard, book-shaped hinged test device. Swab specimens require a sample preparation step, in which the sample is eluted off the swab into a saline solution. The nasal wash sample does not require any preparation. The sample to be tested is added to a pad at the top of the test strip, and the test device is closed. Influenza B antigen present in the sample reacts to bind anti-influenza B conjugated antibody. The resulting antigencomplexes are captured conjugate by anti-influenza antibody, immobilized forming the Sample Line. Immobilized Control Line antibody, which appears as a blue line in an untested device, captures a visualizing conjugate, forming a pink Control Line. The sample is contained, and results are available within 15 minutes.

Here's a breakdown of the acceptance criteria and study details for the Binax NOW® FLU B Test:

Binax NOW® FLU B Test Acceptance Criteria and Study Details

1. Acceptance Criteria and Reported Device Performance

Note: The document primarily uses substantial equivalence to the predicate device as the overarching acceptance criterion, rather than explicit numerical thresholds. The reported performance metrics are presented to demonstrate this equivalence.

2. Sample Sizes and Data Provenance

• Clinical Study Test Set Sample Size:
  • 191 nasal wash specimens
  • 182 nasopharyngeal swab specimens
• Data Provenance:
  • Country of Origin: Not explicitly stated, but the study was described as a "multi-site prospective study," suggesting data collected within the US, given the submission to the FDA.
  • Retrospective/Prospective: Prospective clinical studies. All specimens were "freshly collected and characterized" from "patients presenting with influenza-like symptoms."

3. Number and Qualifications of Experts for Ground Truth

• The document does not specify the number or qualifications of experts used to establish the ground truth for the clinical study.

4. Adjudication Method for the Test Set

• The document does not specify an adjudication method for the test set results beyond comparing the Binax NOW® test performance "versus viral cell culture."

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

• No, a MRMC comparative effectiveness study was not done. This study focuses on the standalone performance of the diagnostic test compared to a laboratory reference method.

6. Standalone Performance Study (Algorithm Only)

• Yes, a standalone performance study was done. The entire "Performance Summary" and "Clinical Sensitivity and Specificity" sections describe the direct comparison of the Binax NOW® test results (the "algorithm only" in this context, as it's a diagnostic device) against viral cell culture (the reference method). There is no mention of a human-in-the-loop component for interpreting the Binax NOW® results in the clinical study beyond the basic reading of the test strip by clinicians/lab personnel.

7. Type of Ground Truth Used

• Viral Cell Culture: This was the primary ground truth used for assessing the clinical sensitivity and specificity of the device. The document states, "Negative test results should be confirmed by cell culture," highlighting its role as the gold standard.

8. Sample Size for the Training Set

• The document does not specify a separate "training set" in the context of machine learning, as this is a rapid immunochromatographic assay. The performance characteristics are based on the described analytical and clinical studies.

9. How Ground Truth for Training Set Was Established

• Since there isn't a "training set" in the machine learning sense for this type of device, this question is not directly applicable. The device's underlying mechanism (immunochromatographic assay) is based on known biological reactions, not a trained algorithm. The analytical and clinical studies serve to validate its performance.

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