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The Focus Diagnostics Simplexa™ Flu A/B & RSV Direct assay is intended for use on the 3M Integrated Cycler instrument for the in vitro qualitative detection and differentiation of influenza A virus, influenza B virus, and respiratory syncytial virus (RSV) RNA in nasopharyngeal swabs (NPS) from human patients with signs and symptoms of respiratory tract infection in conjunction with clinical and epidemiological risk factors. This test is intended for use as an aid in the differential diagnosis of influenza A, influenza B, and RSV viral infections in humans and is not intended to detect influenza C.

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

Performance characteristics for influenza A were established with clinical specimens collected during the 2010/2011 influenza season when 2009 H1N1 influenza and H3N2 were the predominant influenza A viruses in circulation. When other influenza A viruses are emerging, performance characteristics 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 the 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.

Focus Diagnostics' Simplexa™ Flu A/B & RSV Positive Control Pack is intended to be used as a control with the Simplexa™ Flu A/B & RSV Direct kit. This control is not intended for use with other assays or systems.

The Simplexa™ Flu A/B & RSV Direct assay system is a real-time RT-PCR system that enables the direct amplification, delection and differentiation of human influenza A (Flu A) virus RNA, human influenza B (Flu B) virus RNA and RSV RNA from unprocessed nasopharyngeal swabs that have not undergone nucleic acid extraction. The system consists of the Simplexa™ Flu A/B & RSV Direct assay, the 3M Integrated Cycler (with Integrated Cycler Studio Software), the Direct Amplification Disc and associated accessories.

In the Simplexa™ Flu A/B & RSV Direct assay, bi-functional fluorescent probe-primers are used together with corresponding reverse primers to amplify Flu A, Flu B, RSV and internal control RNA. The assay provides three results; conserved regions of influenza A viruses (matrix gene) influenza B viruses (matrix gene) and RSV (M gene) are targeted to identify these viruses in the specimen. An RNA internal control is used to detect RT-PCR failure and/or inhibition.

The 3M Integrated Cycler is a rapid real-time Polymerase Chain Reaction thermocycler used for the identification of nucleic acid from prepared biological samples. The instrument utilizes disk media to contain and to process samples. The instrument uses real time flourometric detection to identify targets within the sample wells. The instrument is controlled by an external computer running the Integrated Cycler Studio software.

Here's a breakdown of the acceptance criteria and study details for the Simplexa™ Flu A/B & RSV Direct assay, based on the provided 510(k) summary:

1. Table of Acceptance Criteria and Reported Device Performance

The acceptance criteria are not explicitly stated as numerical targets in the document. However, the reported performance data from the clinical studies serve as the basis for demonstrating the device's acceptable performance. For clarity, I've listed the reported performance as if those were the implicit acceptance targets for the study.

Analytical Performance (Implicit acceptance criteria based on predicate device or general standards for molecular diagnostics):

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

• Prospective Study Test Set:

  • Sample Size: 722 nasopharyngeal swabs.
  • Data Provenance:
    • Country of Origin: Eastern United States, Mid-Western United States, and Australia.
    • Retrospective or Prospective: Prospective. Samples were collected from 10-Nov-2010 to 11-Mar-2011 (Eastern/Mid-Western US) and 17-Aug-2010 to 20-Oct-2010 (Australia).

• Retrospective Study Test Set:

  • Sample Size: 223 nasopharyngeal swabs.
  • Data Provenance: "Retrospectively banked specimens from patients with signs and symptoms of viral respiratory tract infection." Specific country of origin is not detailed beyond "Three external testing sites." These were banked samples, implying retrospective use for this specific study.

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

The document does not specify an "expert" group to establish ground truth in the traditional sense of medical image or diagnostic interpretation. Instead, the ground truth was established by culture results.

• Number of "Experts": Not applicable as ground truth was established by laboratory culture.
• Qualifications of Those Experts: Not applicable. The "experts" were the laboratory processes and personnel performing the culture assays.

4. Adjudication Method for the Test Set

Not applicable. The ground truth was based on culture results, which inherently serve as a definitive reference method for these types of assays, rather than a consensus among human interpreters. Discrepancies between the device and culture were sometimes resolved by further testing (e.g., FDA cleared NAT/DFA), but this isn't an "adjudication method" in the context of expert review.

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, a Multi-Reader Multi-Case (MRMC) comparative effectiveness study was not done. This type of study is typically performed for imaging or interpretive AI devices where human readers provide an initial diagnosis, and the AI assists in improving their performance. This device is a molecular diagnostic assay, not an AI-assisted interpretive tool.

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

Yes, this was a standalone performance study. The Simplexa™ Flu A/B & RSV Direct assay is a molecular diagnostic test that provides a direct result (detected/not detected) without human interpretive input beyond following the assay's operational procedures. The clinical agreement results compare the device's output directly against the culture gold standard.

7. The Type of Ground Truth Used

The primary ground truth used for both prospective and retrospective clinical studies was culture results.

• For RSV, some discrepancies were confirmed using an FDA-cleared NAT (Nucleic Acid Test) or FDA-cleared DFA (Direct Fluorescent Antibody) test, which could be considered a secondary confirmation of the ground truth for those specific samples.

8. The Sample Size for the Training Set

The document does not provide a specific sample size for a "training set" for an algorithm. This device is a molecular diagnostic assay (RT-PCR system), not an AI/machine learning algorithm that requires a separate training set. The assay's parameters (e.g., probe-primers, thresholds for detection) would have been developed and optimized during its R&D phase, but this doesn't involve "training data" in the AI sense.

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

Not applicable. As noted in point 8, this is not an AI/machine learning device that uses a "training set" with established ground truth in that context. The analytical and clinical performance established the validity of the assay.

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