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The BD Veritor™ System for Rapid Detection of Flu A+B is a rapid chromatographic immunoassay for the direct and qualitative detection of influenza A and B viral nucleoprotein antigens from nasopharyngeal wash, aspirate and swab in transport media samples from symptomatic patients. The BD Veritor System for Rapid Detection of Flu A+B is a differentiated test, such that influenza A viral antigens can be distinguished from influenza B viral a single processed sample using a single device. The test is to be used as an aid in the diagnosis of influenza A and B viral infections. A negative test is presumptive and it is recommended that these results be confirmed by viral culture or an FDA-cleared influenza A and B molecular assay. Outside the U.S. a negative test is presumptive and it is recommended that these results be confirmed by viral culture or a molecular assay cleared for diagnostic use in the country of use. FDA has not cleared this device outside the U.S. Negative test results do not prectude influenza viral infection and should not be used as the sole basis for treatment or other management decisions. The test is not intended to detect influenza C antigens.

The BD Flu A+B test is a chromatographic assay to qualitatively detect influenza A and B viral antigens in respiratory specimens. The patient specimen is mixed in a prefilled unitized tube containing RV Reagent C and added to the test device. RV Reagent C contains mucolytic agents that function to break down mucus in a patient specimen thereby exposing viral antigens and enhancing detection in the assay device. Processed specimens are expressed through a filter tip into a single sample well on the BD Flu A+B test device.

The specimen is mixed and added to the test device where influenza A or influenza B viral antigens bind to anti-influenza antibodies conjugated to detector particles on the BD Flu A+B test strip. The antigen-conjugate complex migrates across the test strip to the reaction area and is captured by an antibody line on the membrane. The assay utilizes a proprietary enhanced colloidal-gold particle at the test lines as the means for identifying the presence of influenza A or B viral antigens. The BD Flu A+B test devices are designed with five spatially-distinct zones including positive and negative control line positions, separate test line positions for the target analytes, and a background zone. The test lines for the target analytes are labeled on the test device as 'A' for Flu A position, and 'B' for Flu B position. The onboard positive control ensures the sample has flowed correctly and is indicated on the test device as 'C'. Two of the five distinct zones on the test device are not labeled. These two zones are an onboard negative control line and an assay background zone. The onboard negative control zone addresses non-specific signal generation and is not labeled on the test device. The remaining zone is used to measure the assay background and is also not labeled.

The BD Flu A+B assay incorporates an active negative control feature in each test to identify and compensate for sample-related, nonspecific signal generation. The BD Veritor™ System Reader uses a proprietary algorithm which subtracts nonspecific signal at the negative control line from the signal present at both the Flu A and Flu B test lines. If the resultant test line signal is above a pre-selected assay cutoff, the specimen is scored as positive. If the resultant test line signal is below the cutoff, the specimen is scored as negative. Use of the active negative control feature allows the BD Veritor™ System reader to correctly interpret test results that cannot be scored visually because the human eye is unable to accurately perform the subtraction of the nonspecific signal.

The BD Veritor™ System Reader measures the amount of light reflected from various zones along the assay strip. The measurement of the assay background zone is an important factor during test interpretation as the reflectance is compared to that of the control and test zones. A background area that is white to light pink indicates the device has performed correctly. The instrument analyzes the reflectance data to provide the proper interpretation.

Here's a breakdown of the acceptance criteria and study information for the BD Veritor™ System for Rapid Detection of Flu A+B (Laboratory Kit), based on the provided document:

Acceptance Criteria and Device Performance

The acceptance criteria for this study were focused on the ability of the BD Veritor Flu A+B assay system to provide a positive instrumented read for samples of new influenza virus strains. The "reported device performance" reflects the successful detection of all tested strains.

Study Details

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

• Sample Size for Test Set: 14 influenza virus strains (9 Flu A strains and 5 Flu B strains).
• Data Provenance: The viral material was obtained from the WHO Collaborating Centre for Surveillance, Epidemiology and Control of Influenza and the US Centers for Disease Control (CDC). Two strains were provided by the National Institute for Biological Standards and Control (UK). The study was conducted at the R/D laboratories in San Diego, CA, USA. This was a prospective study specifically designed to test the reactivity of the device against these new strains.

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

• Number of Experts: The document does not explicitly state the number of experts used to establish the ground truth for the test set. However, the viral material was provided by recognized expert organizations (WHO, CDC, NIBSC), implying that the characterization and titering of these virus strains were performed by qualified virologists or equivalent experts within those institutions.
• Qualifications of Experts: Not detailed for individual experts, but the providing organizations are leading authorities in influenza surveillance and characterization.

4. Adjudication Method for the Test Set

The document does not describe an adjudication method involving multiple readers for the test set results. The BD Veritor System Reader uses a proprietary algorithm to interpret test results by subtracting non-specific signals. The "acceptance criteria was the ability of the BD Veritor test to detect these additional Flu strains," which suggests a direct measurement of instrument output against known viral presence.

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

No, an MRMC comparative effectiveness study was not conducted. This study focused on the analytical performance (reactivity and limit of detection) of the device itself against specific viral strains, not on human reader performance with or without AI assistance. The BD Veritor System Reader automatically interprets the results, removing the subjective human-in-the-loop element for interpretation.

6. Standalone (Algorithm Only Without Human-in-the-Loop) Performance

Yes, a standalone study was performed. The BD Veritor System Reader automatically interprets test results based on its proprietary algorithm without human interpretation of the signal. The "instrumented read" and the calculation of LODs by the device confirm its standalone performance. The document explicitly states: "The BD Veritor™ System Reader uses a proprietary algorithm which subtracts nonspecific signal at the negative control line from the signal present at both the Flu A and Flu B test lines. If the resultant test line signal is above a pre-selected assay cutoff, the specimen is scored as positive. If the resultant test line signal is below the cutoff, the specimen is scored as negative."

7. Type of Ground Truth Used

The ground truth used was the presence and quantified titer of specific influenza viral strains. These strains were obtained from reputable public health organizations (WHO, CDC, NIBSC) and their titers (e.g., CEID50/mL, EID50/mL, TCID50/mL, HA) were known and confirmed through standard virological methods (e.g., MDCK cell culture, Reed-Muench formula for TCID50 calculation).

8. Sample Size for the Training Set

The document does not specify a training set or its sample size. This particular submission is a Special 510(k) for a device modification (labeling update with new strain reactivity data) for an already cleared device (K120049, K121797, K132256, K132693, K133138). The BD Veritor™ System uses a proprietary algorithm, but the details of its original development and training data are not part of this specific submission. This study is an analytical validation testing the device's ability to detect newly identified or relevant strains.

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

As no specific training set is detailed in this document, the method for establishing its ground truth is not provided. For the current analytical validation study, the ground truth was established by acquiring known, characterized influenza viral materials with quantified titers from established public health and research institutions.

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