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The Innovita Flu A/B Antigen Rapid Test is a rapid chromatographic immunoassay intended for the qualitative detection and differentiation of influenza A and B viral nucleoprotein antigens directly from nasopharyngeal swabs from patients with signs and symptoms of respiratory infection.

The test is intended for use as an aid in the differential diagnosis of acute influenza A and B viral infections. The test is not intended to detect influenza C antigens. Negative test results are presumptive and should be confirmed by viral culture or an FDA-cleared influenza A and B molecular assay. Negative test results do not preclude influenza viral infection and should not be used as the sole basis for treatment or other patient management decisions.

Performance characteristics for influenza A were established during the December 2023, and July 2024 influenza season when influenza A/H1N1pdm09, influenza A/H3N2 and influenza B/Victoria viruses were the predominant influenza viruses in circulation. When other influenza A viruses are emerging, performance characteristics may vary.

If an 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 Innovita Flu A/B Antigen Rapid Test is a double antibody sandwich immunoassay-based test. The test device consists of the specimen zone and the test zone. The specimen zone contains monoclonal antibody against the Flu A/Flu B antigen labeled with latex microspheres and chicken IgY antibody conjugated with latex microspheres. The test line contains the other monoclonal antibody against Flu A/Flu B antigen. The control line contains rabbit anti-chicken IgY antibody.

After the specimen is applied into the specimen well of the device, antigen in the specimen forms an immune complex with the binding reagent in the specimen zone. Then the complex migrates to the test zone. The test line in the test zone contains antibody from a specific pathogen. If the concentration of the specific antigen in the specimen is higher than LoD of Flu A or Flu B, it will be captured at Flu A or Flu B line and form a red-purple line. In contrast, if the concentration of the specific antigen is lower than LoD, it will not form a red-purple line. The test also contains an internal control system. A red-purple control line (C) should always appear after the test is completed. Absence of a red-purple control line indicates an invalid result. The product contents are listed below.

Here's an analysis of the acceptance criteria and the study proving the device meets them, based on the provided FDA 510(k) clearance letter:

Acceptance Criteria and Device Performance for Innovita Flu A/B Antigen Rapid Test

1. Table of Acceptance Criteria and Reported Device Performance

The provided document does not explicitly state pre-defined acceptance criteria for the clinical study's Positive Percent Agreement (PPA) and Negative Percent Agreement (NPA). However, the reported device performance is presented. For analytical performance (LoD, inclusivity, cross-reactivity, interfering substances), the acceptance criterion is generally 100% agreement or no interference/cross-reactivity as implied by the reported results.

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

• Test Set Sample Size (Clinical Study): 1101 evaluable nasopharyngeal swab specimens.
• Data Provenance:
  • Country of Origin: U.S.
  • Study Type: Prospective clinical study. Specimens were collected from subjects with flu-like symptoms during the 2023-2024 influenza season.

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

The ground truth for the clinical test set was established using an "FDA-cleared influenza A and B molecular assay" as the comparator method. The document does not specify the number of human experts involved in establishing this ground truth or their qualifications. The ground truth relies on the performance characteristics of the molecular assay itself.

4. Adjudication Method for the Test Set

The document does not describe any adjudication method (e.g., 2+1, 3+1) for the clinical test set results. The comparison appears to be a direct one-to-one comparison between the Innovita Flu A/B Antigen Rapid Test result and the result from the FDA-cleared molecular assay.

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

No MRMC comparative effectiveness study was done comparing human readers with AI vs. without AI assistance. This device is a rapid diagnostic test (RDT) with visual interpretation. The precision study involved "untrained operators" to assess reproducibility, but it was not a comparative effectiveness study with or without AI assistance.

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

Yes, this study primarily assesses the standalone performance of the rapid diagnostic test device. While human operators interpret the visual results, the performance metrics (PPA, NPA) are based on the device's output compared to the ground truth, without an explicit human-in-the-loop component being evaluated for its improvement with AI, as there is no AI component mentioned for interpretation.

7. Type of Ground Truth Used

The ground truth for the clinical study was: Comparator Method (FDA-cleared influenza A and B molecular assay).

8. Sample Size for the Training Set

The document does not explicitly state a sample size for a "training set." Rapid diagnostic tests typically do not involve machine learning algorithms that require a distinct training set in the same way an AI/ML device would. The development of the assay (e.g., antibody selection, optimization) is a different process from training a machine learning model.

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

Since a "training set" in the context of machine learning is not explicitly mentioned or applicable for this type of rapid diagnostic test, the method for establishing its ground truth is not applicable/not described. The analytical studies (LoD, inclusivity, specificity) use laboratory-prepared, characterized samples with known viral concentrations or presence/absence, serving as the "ground truth" for those specific analytical evaluations.

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