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The Alere™ i Influenza A & B 2 assay performed on the Alere™ i Instrument is a rapid molecular in vitro diagnostic test utilizing an isothermal nucleic acid amplification technology for the qualitative detection and discrimination of influenza A and B viral RNA in direct nasal or nasopharyngeal swabs and nasal or nasopharyngeal swabs eluted in viral transport media from patients with signs and symptoms of respiratory infection. It is intended for use as an aid in the differential diagnosis of influenza A and B viral infections in humans in conjunction with clinical and epidemiological risk factors. The assay is not intended to detect the presence of influenza C virus.

Negative results do not preclude influenza virus infection and should not be used as the sole basis for diagnosis, treatment or other patient management decisions.

Performance characteristics for influenza A were established during the 2016-2017 influenza season when influenza A/H3 and A/H1N1 pandemic were the predominant influenza A viruses in circulation. When other influenza A viruses are emerging, performance characterics may vary.

If 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 cases unless a BSL 3+ facility is available to receive and culture specimens.

Alere™ i Influenza A & B 2 is a rapid, instrument-based isothermal test for the qualitative detection and differentiation of influenza A and influenza B from nasal swabs tested directly or after elution in viral transport media collected from patients with signs and symptoms of respiratory infection. The Alere™ i Influenza A & B 2 System utilizes isothermal nucleic acid amplification technology and is comprised of:

• Sample Receiver single use, disposable containing the elution buffer
• Test Base single use, disposable comprising two sealed reaction tubes, each containing a lyophilized pellet
• Transfer Cartridge – Single use, disposable for transfer of the eluted sample to the Test Base, and
• Alere™ i Instrument - repeat use reader

The reaction tubes in the Test Base contain the reagents required for amplification of the target nucleic acid and an internal control. Alere™ i Influenza A & B 2 utilizes a pair of templates (similar to primers) for the specific amplification of RNA from influenza A and B, which occur in two separate reaction tube contains fluorescently labeled molecular beacon designed to specifically identify the amplified RNA targets. Alere™ i Influenza A & B 2 is performed within the confinement of the Test Base, and no other part of the Alere™ i Instrument has contact with the sample during the amplification process. This minimizes the risk of instrument contamination and sample carry-over between measurements.

To perform the assay, the Sample Receiver and Test Base are inserted into the Alere™ i Instrument and the elution buffer is automatically heated by the instrument. The sample is added to the Sample Receiver and transferred via the Transfer Cartridge to the Test Base, re-suspending the lyophilized pellets contained within the Test Base and initiating target amplification. Heating, mixing and detection by fluorescence are provided by the instrument, with results automatically reported.

Results are displayed by the Alere™ i Instrument and are also stored in an on-board archive and are assigned to a sample ID that has been entered into the Alere™ i Instrument by the operator, and the date/time the test was performed. Data can be retrieved and downloaded by the operator at any time after testing. An external Alere™ Universal Printer can be attached via USB to the Alere™ i Instrument to print test results.

Here's an analysis of the acceptance criteria and study detailed in the provided text:

1. Table of Acceptance Criteria and Reported Device Performance

The document does not explicitly state pre-defined acceptance criteria (e.g., "the device must achieve X sensitivity and Y specificity"). Instead, it presents the device's performance, which is implicitly accepted by the FDA's "Substantially Equivalent" determination. The table below summarizes the reported clinical performance.

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

• Sample Size:
  • Total enrolled: 1110 nasal or nasopharyngeal swab specimens.
  • Total tested:
    • 1070 for direct swab performance analysis (after excluding 36 not meeting eligibility and 4 invalid after re-testing).
    • 1057 for viral transport media (VTM) performance analysis (after excluding 36 not meeting eligibility, 11 invalid after re-testing, and 6 not meeting eligibility).
• Data Provenance:
  • Country of Origin: United States (multi-center, conducted at ten US trial sites).
  • Retrospective or Prospective: Prospective clinical study.

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

The ground truth for the clinical study was established using an FDA-cleared real-time Polymerase Chain Reaction (RT-PCR) test as the comparator method. The document does not mention the use of human experts (e.g., radiologists) to establish ground truth for this device, as it is an in vitro diagnostic test for viral RNA detection, not an imaging device.

4. Adjudication Method for the Test Set

The ground truth was established by a single comparator method (FDA-cleared RT-PCR). There is no mention of an adjudication method for the test set, as the RT-PCR result was considered the definitive truth. For discrepancies, secondary molecular testing was used to investigate false positives/negatives (e.g., "Flu A nucleic acid was detected in 6/21 False positive specimens using a second FDA-cleared molecular test"). This refers to investigation of the Alere™ i results against the initial RT-PCR, not an adjudication process to establish the initial ground truth.

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

No MRMC comparative effectiveness study was done. This type of study is typically relevant for interpretative devices (e.g., medical imaging AI) where human readers are involved in the diagnostic process. The Alere™ i Influenza A & B 2 is an automated molecular diagnostic test with automated result interpretation.

6. Standalone Performance

Yes, a standalone performance study was done. The clinical study results (sensitivity, specificity, invalid rates) reported for the device directly reflect its performance as an algorithm-only (kit + instrument) system without human-in-the-loop interpretation beyond operating the instrument and reading the automated result. The "automated result interpretation" listed in the device comparison table further confirms its standalone nature.

7. Type of Ground Truth Used

The primary ground truth used for the clinical performance evaluation was an FDA-cleared real-time Polymerase Chain Reaction (RT-PCR) test. This is a molecular diagnostic method considered highly accurate for detecting viral RNA. Secondary molecular testing was used to investigate discordant results.

8. Sample Size for the Training Set

The document does not specify the sample size for the training set. It details the clinical validation (test set) and analytical studies. Typically, for such devices, the training data would be proprietary to the manufacturer and not explicitly disclosed in an FDA 510(k) summary, which focuses on validation data.

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

Since the training set data is not disclosed, the method for establishing its ground truth is also not described in this document. It is generally assumed that the training data for molecular diagnostic assays would be similarly characterized using highly accurate reference methods, potentially including PCR, sequencing, or well-characterized viral cultures.

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