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The Panther Fusion SARS-CoV-2/Flu A/B/RSV assay is a fully automated multiplexed real-time polymerase chain reaction (RT-PCR) in vitro diagnostic test intended for the qualitative detection and differentiation of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), influenza A virus (Flu A), influenza B virus (Flu B), and respiratory syncytial virus (RSV). Nucleic acids are isolated and purified from nasopharyngeal (NP) swab specimens and anterior nasal (AN) swab specimens obtained from individuals exhibiting signs and symptoms of a respiratory tract infection. Clinical signs and symptoms of respiratory viral infection due to SARS-CoV-2, influenza, and RSV can be similar. This assay is intended to aid in the differential diagnosis of SARS-CoV-2, Flu A, Flu B, and RSV infections in humans and is not intended to detect influenza C virus infections.

Nucleic acids from the viral organisms identified by this test are generally detectable in NP and AN swab specimens during the acute phase of infection and identification of specific viral nucleic acids from individuals exhibiting signs and symptoms of respiratory tract infective of the presence of the identified virus and aids in diagnosis if used in conjunction with other clinical and epidemiological information, and laboratory findings. The results of this test should not be used as the sole basis for diagnosis, treatment, or other patient management decisions. Positive results do not rule out coinfection with other organism(s) detected by the Panther Fusion SARS-CoV-2/Flu A/B/RSV assay may not be the definite cause of disease. Negative results do not preclude SARS-CoV-2, influenza A virus, influenza B virus, or RSV infections. This assay is designed for use on the Panther Fusion system.

The Hologic RespDirect Collection Kit is cleared for NP swab specimens only for testing with the Panther Fusion SARS-CoV-2/Flu A/B/RSV assay.

The Panther Fusion SARS-CoV-2/Flu A/B/RSV assay is classified as a Class II in vitro diagnostic device per 21 CFR 866.3981 and has product code QOF. The Panther Fusion SARS-CoV-2/Flu A/B/RSV assay is designed for use on the fully automated Panther Fusion System.

The Panther Fusion system is a class II exempt device under 21CFR 862.2570 that has product code OOI.

The Panther Fusion SARS-CoV-2/Flu A/B/RSV assay is a multiplex real-time reverse transcriptase PCR (RT-PCR) in vitro diagnostic test developed for use on the fully automated Panther Fusion system to detect and differentiate SARS-CoV-2, influenza A, influenza B, and respiratory syncytial virus (RSV) directly from nasopharyngeal and anterior nasal swab specimens, from individuals exhibiting signs and symptoms of a respiratory tract infection.

The Panther Fusion SARS-CoV-2/Flu A/B/RSV assay involves the following steps: sample lysis, nucleic acid capture and elution transfer, and multiplex RT-PCR where analytes (when present) are simultaneously amplified, detected and differentiated. Nucleic acid capture and elution takes place in a single tube on the Panther Fusion system. The eluate is transferred to the Panther Fusion system reaction tube containing the assay reagents. Multiplex RT-PCR is then performed for the eluted nucleic acid on the Panther Fusion system.

Here's a breakdown of the acceptance criteria and the study details for the Panther Fusion SARS-CoV-2/Flu A/B/RSV assay, based on the provided document:

1. Table of Acceptance Criteria and Reported Device Performance

Note on Acceptance Criteria: The document explicitly states the goal is to demonstrate "comparable" performance to the predicate device (which uses an NP swab) for the new anterior nasal (AN) swab specimen type. While specific numerical acceptance criteria (e.g., "PPA must be >X%") are not provided in this summary, the reported performance metrics (PPA, NPA, and their confidence intervals) are presented to demonstrate this comparability and overall effectiveness for diagnostic use, as typical for molecular assays expanding their indications. The high NPA values for all targets indicate good specificity, and generally high PPA values indicate good sensitivity, especially when considering the confidence intervals. The lower PPA for Flu B in the prospective study was addressed and supported by the retrospective study, which showed strong performance.

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

• Prospective Clinical Study (Anterior Nasal Swab):

  • Sample Size: 1,268 individuals were enrolled. 1,230 AN swab specimens were tested, resulting in 1,189 evaluable specimens for analysis (not all evaluable for all analytes).
  • Data Provenance: Prospective, multicenter study conducted in the US. Specimens were collected from individuals attending nine participating medical facilities in the US during the 2022-2023 respiratory infection season.

• Retrospective Clinical Study (Anterior Nasal Swab - Supplement for Flu B and RSV):

  • Sample Size: 175 preselected retrospective specimens.
  • Data Provenance: Retrospective. The origin country is not explicitly stated but is implied to be related to the US context from the prospective study.

• Analytical Studies (Reprocessing from K222736):

  • Sample Size: Not explicitly stated as "sample size" for each analytical study detail, but refers to the number of replicates/conditions tested for LOD, inclusivity, exclusivity, etc. For example, Flu B LoD confirmation involved 28 replicates per panel.
  • Data Provenance: Already existing data from the previous 510(k) submission (K222736) using Nasopharyngeal (NP) swabs, reprocessed with the updated software.

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

The document does not mention the use of experts to establish ground truth for the clinical test sets. Instead, the ground truth was established by comparing the candidate device's results to reference molecular assays:

• SARS-CoV-2: A composite comparator algorithm (CCA) consisting of up to three highly sensitive US FDA EUA SARS-CoV-2 molecular tests. A final CCA result was assigned when two of the three comparator assays were in concordance.
• Flu A, Flu B, and RSV: A US FDA-cleared molecular Flu A/B/RSV assay.

4. Adjudication Method for the Test Set

• SARS-CoV-2 Ground Truth: For SARS-CoV-2, a composite comparator algorithm (CCA) was used. A final CCA result was assigned when "two of the three composite comparator assays were in concordance." This effectively acts as an adjudication method where agreement among a majority of reference tests determines the ground truth.
• Flu A, Flu B, RSV Ground Truth: For Flu A, Flu B, and RSV, a single "US FDA-cleared molecular Flu A/B/RSV assay" was used as the comparator method. There's no mention of an adjudication process among multiple comparators for these targets.

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

• No, a Multi-Reader Multi-Case (MRMC) comparative effectiveness study was not explicitly mentioned or conducted. This type of study is more common for imaging devices or diagnostics that involve subjective interpretation by human readers. This device is an automated molecular diagnostic assay, where the output is objective (positive/negative, Ct value).

6. Standalone (Algorithm Only) Performance Study

• Yes, the performance data presented (PPA, NPA) directly reflects the standalone performance of the Panther Fusion SARS-CoV-2/Flu A/B/RSV assay. It is compared to a ground truth established by other molecular tests, without human interpretation of the assay's output influencing the performance metrics. The assay itself is automated, so its performance is inherently "algorithm only" in the context of generating results.

7. Type of Ground Truth Used

• Molecular Comparator Assays: The ground truth for the clinical test sets (both prospective and retrospective) was established using other legally marketed and highly sensitive molecular diagnostic tests.
  • For SARS-CoV-2: A composite of up to three US FDA EUA SARS-CoV-2 molecular tests.
  • For Flu A, Flu B, RSV: A US FDA-cleared molecular Flu A/B/RSV assay.

8. Sample Size for the Training Set

• The document does not explicitly state the sample size used for the training set. This submission focuses on the validation of an existing assay with a new specimen type (anterior nasal swab) and a software update (Adaptive Crosstalk Correction). The original development and training data for the core assay (K222736) would have been described in that prior submission, but are not detailed here for this specific submission's scope. The mention of "reprocessed with validated Results Processor Tool" for previously submitted analytical studies also suggests reuse of data rather than new training.

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

• Since the document doesn't explicitly detail a new "training set" for this specific submission, it also doesn't describe how ground truth for such a set was established. It's likely that the original assay development followed similar methods of using well-characterized samples or comparator assays for internal development and optimization.
• Regarding the Adaptive Crosstalk Correction (ACC) factor, the validation involved "testing of SARS-CoV-2 positive clinical specimens that are representative of those that yielded false positive Flu B results in the field." This indicates that the problem the ACC addresses arose from real-world performance, and the resolution was validated against specific clinical scenarios rather than a formal "training set" in the machine learning sense.

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