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The xTAG Respiratory Viral Panel (RVP) is a qualitative nucleic acid multiplex test intended for the simultaneous detection and identification of multiple respiratory virus nucleic acids in nasopharyngeal swabs from individuals suspected of respiratory tract infections. The following virus types and subtypes are identified using RVP: Influenza A. Influenza A subtype H1, Influenza A subtype H3, Influchza B, Respiratory Syncytial Virus subtype A, Respiratory Syncytial Virus subtype B, Parainfluenza 1, Parainfluenza 2, and Parainfluenza 3 virus. Human Metapneumovirus, Rhinovirus, and Adenovirus. The detection and identification of specific viral nucleic acids from individuals exhibiting signs and symptoms of respiratory infection aids in the diagnosis of respiratory viral infection if used in conjunction with other clinical and laboratory findings. It is recommended that specimens found to be negative for Influenza B, Respiratory Synctial Virus subtype A and B, Parainfluenza 2, Parainfluenza 3 and Adenovirus, after examination using RVP be confirmed by cell culture. Negative results do not preclude respiratory virus infection and should not be used as the sole basis for diagnosis, treatment or other management decisions. Positive results do not rule out bacterial infection, or co-infection with other viruses. The agent detected may not be the definite cause of disease. The use of additional laboratory testing (e.g. bacterial culture, immunofluorescence, radiography) and clinical presentation must be taken into consideration in order to obtain the final diagnosis of respiratory viral infection.

Due to seasonal prevalence, performance characteristics for Influenza A/H1 were established primarily with retrospective specimens.

The RVP assay cannot adequately detect Adenovirus species C, or serotypes 7a and 41. The RVP primers for detection of thinovirus cross-react with enterovirus. A rhinovirus reactive result should be confirmed by an alternate method (e.g. cell culture).

Performance characteristics for Influenza A Virus were established when Influenza A/H3 and A/H1 were the predominant Influenza A viruses in circulation. When other Influenza A viruses are emerging, performance characteristics may vary. If infections 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 a 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 xTAG Respiratory Viral Panel includes the following components:

• Multiplex PCR primer mix (without dNTPs) .
• Multiplex target specific primer extension (TSPE) primers (includes dNTPs) .
• Coupled bead mix .
• 10x buffer
• xTAG® Data Analysis Software (TDAS RVP-I) .

Here's a summary of the acceptance criteria and study information for the xTAG® RVP device, based on the provided 510(k) summary:

The 510(k) summary provided primarily focuses on establishing substantial equivalence to a predicate device and specifically details the device's ability to detect novel 2009 Influenza A/H1N1 strains, rather than establishing acceptance criteria against a predefined performance target in a typical clinical trial format.

Key takeaway: The document highlights the device's performance in identifying the 2009 Influenza A/H1N1 strain, which was a new and important consideration at the time of this 510(k) submission. It describes how the device handles this specific strain compared to a reference method (CDC rRT-PCR assay).

1. Table of Acceptance Criteria and Reported Device Performance

The provided document doesn't explicitly state quantitative acceptance criteria (e.g., minimum sensitivity, specificity thresholds) for the device's overall performance as would be expected in a typical clinical study report for initial market clearance. Instead, it demonstrates the device's capability to detect a newly emerging influenza strain. The "acceptance" can be inferred as the ability to effectively detect the 2009 Influenza A/H1N1 strain, often by agreement with a reference method.

• Out of 141 "unsubtypeable" Flu A samples by xTAG RVP, 101 were further tested with CDC rRT-PCR.
• 99 out of 101 (98.0%) identified as positive for 2009 Influenza A/H1N1 by CDC rRT-PCR (CT37) by CDC rRT-PCR and by xTAG RVP, and could not be classified as 2009 Influenza A/H1N1 positive.

Study 2 (Ginocchio et al., 2009):

• Out of 1265 samples positive for Influenza A by xTAG RVP, 1108 were "flu A unsubtypeable".
• All 1108 (100%) "flu A unsubtypeable" samples were confirmed to be Influenza A/H1N1 with the CDC rRT-PCR assay. |
  | Identification of other respiratory viruses | The device identified Influenza B (2 samples) and other respiratory viruses including adenovirus, metapneumovirus, Parainfluenza 1, 2, 3, RSV, and rhinovirus (58 samples) in the Ginocchio & George (2009) study, alongside the Influenza A positives. |
  | Subtyping of seasonal Influenza A strains | In the Ginocchio & George (2009) study, 60 Flu A positive samples were identified by xTAG RVP as seasonal strains (2 as H1 and 58 as H3). |

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

• Study 1 (Ginocchio & George, 2009):
  • Initial samples tested with various methods: 1,382 nasopharyngeal swab samples.
  • Samples further tested with xTAG RVP: 375 samples (positive for Influenza A by other methods or from high-risk patients).
  • Samples identified as "unsubtypeable" Flu A by xTAG RVP: 141.
  • Test Set for 2009 H1N1 confirmation: 101 frozen residual samples out of the 141 unsubtypeable samples.
  • Data Provenance: Retrospective specimens from the 2009 Influenza A H1N1 (swine flu) outbreak in New York.
• Study 2 (Ginocchio et al., 2009):
  • Test Set: 2,715 nasopharyngeal swab samples.
  • Data Provenance: Not explicitly stated, but context suggests it's related to 2009 Influenza A/H1N1 surveillance, likely also retrospective and from the outbreak regions.

3. Number of Experts Used to Establish Ground Truth and Qualifications

The studies described use a highly sensitive and specific laboratory reference method, not expert human readers, to establish ground truth.

• Ground truth was established by the CDC rRT-PCR assay for 2009 Influenza A H1N1 (swine flu). This is a highly specialized molecular diagnostic test, and the "experts" would be the trained laboratory personnel performing and interpreting this assay. Specific qualifications beyond performing the reference assay are not detailed.

4. Adjudication Method for the Test Set

Not applicable. The ground truth was established by a laboratory reference method (CDC rRT-PCR assay), not through human reader adjudication.

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

No, a multi-reader multi-case (MRMC) comparative effectiveness study was not performed. The device is a diagnostic assay, and its performance is typically evaluated against laboratory reference standards or clinical outcomes, not against variations in human reader interpretation of images or signals.

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

Yes, the studies describe the standalone performance of the xTAG RVP assay. While the assay requires laboratory personnel to run the test and interpret results from the xTAG® Data Analysis Software (TDAS RVP-I), the performance metrics reported (e.g., number of positives concordant with CDC rRT-PCR) reflect the assay's direct detection capabilities, independent of human clinical interpretation of symptoms or subsequent reader adjustments.

7. Type of Ground Truth Used

The primary ground truth used for confirming the detection of 2009 Influenza A/H1N1 was a laboratory reference method: the CDC rRT-PCR assay for 2009 Influenza A H1N1. This is a highly sensitive and specific molecular test, considered the gold standard for identifying this specific viral strain at the time.

For other viruses, the general intended use suggests confirmation by cell culture for negative results of certain viruses, but the performance studies specifically for 2009 H1N1 used the CDC PCR assay as ground truth.

8. Sample Size for the Training Set

The document does not specify a separate training set or its sample size. The studies described are performance evaluations on clinical samples, likely acting as a test set for the already developed assay. Diagnostic molecular assays typically establish their core design and parameters through internal development and validation, and these clinical studies serve to demonstrate performance on real-world samples.

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

Not applicable, as a distinct training set with its own ground truth establishment is not detailed in the provided summary. The clinical samples evaluated in the studies served as performance verification, using the CDC rRT-PCR as the ground truth comparator.

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