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The Light Diagnostics SimulFluor™ Flu A/Flu B Immunofluorescence Assay is intended for the detection and identification of influenza A and influenza B in respiratory specimens such as throat, nasal and nasopharyngeal swabs, nasopharyngeal aspirates, broncho-alveolar lavages from patients with febrile respiratory illness and following amplification of virus in cell culture. Specimens found to be negative on direct specimen examination must be confirmed with culture. For in vitro diagnostic use.

Light Diagnostics SimulFluor™ Flu A/Flu B Immunofluorescence Assay utilizes a single reagent for the simultaneous detection and identification of influenza A and influenza B. The primary component, specific for influenza A, will bind to influenza A nucleoprotein in influenza A-infected cells. The secondary component, specific for influenza B, will bind to influenza B nucleoprotein in influenza B-infected cells. Unbound reagent is removed by rinsing with phosphate-buffered saline (PBS). The complexes are visualized with a fluorescence microscope. The influenza A antigenantibody complex will exhibit an apple-green fluorescence and the influenza B antigenantibody complex will be yellow-gold. Uninfected cells stain a dull red due to the presence of Evans blue in the reagent. antibodies ensures increased specificity of the reagent and reduces the risk of non-specific background or interference.

The "Light Diagnostics SimulFluor™ Flu A/Flu B Immunofluorescence Assay" is intended for the detection and identification of influenza A and influenza B in respiratory specimens.

Here's an analysis of the acceptance criteria and the study that proves the device meets them:

1. Table of Acceptance Criteria and Reported Device Performance

The document does not explicitly state pre-defined acceptance criteria in terms of specific sensitivity and specificity thresholds. However, the conclusion states that the device was shown to be "substantially equivalent" to predicate devices, implying that its performance characteristics were deemed acceptable compared to established methods.

Here's a table summarizing the reported device performance in the clinical evaluation against the cultural gold standard for direct patient specimens:

The document also provides performance relative to predicate devices for culture confirmation, which consistently show 97.8% to 100% sensitivity and 100% specificity for both Influenza A and B, suggesting the device performs very well in this context.

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

• Sample Size for Test Set:
  • Site 1: 147 specimens
  • Site 2: 252 specimens
• Data Provenance: The data is from "clinical evaluation" using "patient specimens." The specific country of origin is not explicitly stated, but given the submission is to the FDA, it is highly likely to be the USA. The study design appears to be prospective or a cross-sectional study collecting current patient specimens for evaluation, as it compares the new device's results to a "culture confirmation" method for those specimens.

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

The document does not specify the number or qualifications of experts involved in establishing the ground truth. It refers to "culture confirmation" as the gold standard. For laboratory culture, the interpretation would typically be done by trained laboratory personnel (e.g., medical technologists, microbiologists), but their specific qualifications or number are not detailed.

4. Adjudication Method for the Test Set

The document does not mention an adjudication method for the test set. Given that "culture confirmation" is used as the ground truth, it implies that the culture results themselves were considered definitive without needing further independent adjudication of the initial test results.

5. If a Multi-Reader, Multi-Case (MRMC) Comparative Effectiveness Study Was Done

No, a multi-reader, multi-case (MRMC) comparative effectiveness study was not done. This study focuses on the standalone performance of the immunofluorescence assay against a gold standard (culture) and in comparison to predicate devices, not on human reader performance with or without AI assistance.

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

Yes, a standalone performance evaluation was done. The Light Diagnostics SimulFluor™ Flu A/Flu B Immunofluorescence Assay is a laboratory test, and its "performance characteristics" (sensitivity, specificity) were assessed directly. The "visualization with a fluorescence microscope" is a human-in-the-loop step, but the performance metrics are of the device (the reagent's ability to correctly stain infected cells) against the gold standard, implying a standalone evaluation of the diagnostic method itself, interpreted by a human.

7. The Type of Ground Truth Used

The primary ground truth used for the clinical evaluation was culture confirmation. This means that after initial testing, specimens were cultured to grow and identify the influenza virus, providing a definitive diagnosis against which the immunofluorescence assay's results were compared.

8. The Sample Size for the Training Set

The document does not specify a training set for the device. Immunofluorescence assays typically rely on the specificity of monoclonal antibodies rather than machine learning algorithms that require separate training and test sets. The "non-clinical evaluation" involving testing against various microorganisms and cell lines can be considered an initial validation or characterization, but not a "training set" in the machine learning sense.

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

Since there is no explicit training set in the context of the device's development as described, the method for establishing its ground truth is not applicable. The "non-clinical evaluation" involved challenging the conjugated monoclonal antibodies with known viruses and bacteria, where the "ground truth" was the identity of the specific microorganism.

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