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The Xpert Xpress CoV-2/Flu/RSV plus test, performed on the GeneXpert Xpress System, is an automated multiplexed real-time reverse transcriptase polymerase chain reaction (RT-PCR) test intended for use in the simultaneous in vitro qualitative detection and differentiation of severe acute respiratory syndrome coronavirus (SARS-CoV-2), influenza A, influenza B, and/or respiratory syncytial virus (RSV) viral RNA in nasopharyngeal swab and anterior nasal swab specimens collected from individuals with signs and symptoms of respiratory tract infection. Clinical signs and symptoms of respiratory tract infection due to SARS-CoV-2, influenza A, influenza B, and RSV can be similar.

The Xpert Xpress CoV-2/Flu/RSV plus test is intended for use in the differential detection of SARS-CoV-2, influenza A, influenza B and/or RSV RNA and aids in the diagnosis of COVID-19, influenza and/or RSV infections if used in conjunction with other clinical and epidemiological information, and laboratory findings. SARS-CoV-2, influenza A, influenza B, and RSV viral RNA are generally detectable in nasopharyngeal swab and anterior nasal swab specimens during the acute phase of infection.

Positive results are indicative of the presence of the identified virus, but do not rule out bacterial infection or co-infection with other pathogens not detected by the test. The agent (s) detected by the Xpert Xpress CoV-2/Flu/RSV plus test may not be the definite cause of the disease.

Negative results do not preclude SARS-CoV-2, influenza A, influenza B and/or RSV infection. The results of this test should not be used as the sole basis for diagnosis, treatment or other patient management decisions.

The Xpert Xpress CoV-2/Flu/RSV plus test is an automated in vitro diagnostic test for the simultaneous qualitative detection and differentiation of SARS-CoV-2, Flu A, Flu B, and RSV viral RNA in nasopharyngeal swab (NPS) and anterior nasal swab (NS) specimens collected from individuals showing signs and symptoms of respiratory viral infection.

The Xpert Xpress CoV-2/Flu/RSV plus test is performed on GeneXpert Xpress System, which consist of a GeneXpert IV instrument that executes sample preparation, nucleic acid amplification and real-time fluorescent signal detection for the tests, and a GeneXpert Hub with preloaded GeneXpert Xpress software for running the tests and viewing the test results. The GeneXpert Hub accessory integrates the computer, touchscreen monitor and barcode scanner. Each of the GeneXpert modules in the GeneXpert IV instrument can perform independent sample preparation and testing. The GeneXpert Xpress System requires the use of single-use disposable cartridges that hold the RT-PCR reagents and host sample purification, nucleic acid amplification, and detection of the target sequences. Because the cartridges are self-contained, cross-contamination between samples is minimized.

The Xpert Xpress CoV-2/Flu/RSV plus test includes reagents for the detection of SARS-CoV-2, Flu A, Flu B and RSV viral RNA from NPS and NS specimens. The primers and probes in the Xpert Xpress CoV-2/Flu/RSV plus test are designed to amplify and detect unique sequences in the genes that encode the following proteins: SARS-CoV-2 nucleocapsid (N), SARS-CoV-2 envelope (E), SARS-CoV-2 RNA-dependent RNA polymerase (RdRP), influenza A matrix (M), influenza A basic polymerase (PB2), influenza A acidic protein (PA), influenza B matrix (M), influenza B non-structural protein (NS), and the RSV A and RSV B nucleocapsid.

A Sample Processing Control (SPC) and a Probe Check Control (PCC) are also included in the cartridge utilized by the GeneXpert instrument. The SPC is present to control for adequate processing of the sample and to monitor for the presence of potential inhibitor(s) in the RT-PCR reaction. The SPC also ensures that the RT-PCR reaction conditions (temperature and time) are appropriate for the amplification reaction and that the RT-PCR reagents are functional. The PCC verifies reagent rehydration, PCR tube filling, and confirms that all reaction components are present in the cartridge including monitoring for probe integrity and dye stability.

The Xpert Xpress CoV-2/Flu/RSV plus test is designed for use with NPS or NS specimens collected with nylon flocked swabs and placed into viral transport medium (VTM), Universal Transport Medium (UTM), or eNAT®. The ancillary specimen collection kits, swabs and transport media validated for use with the Xpert Xpress CoV-2/Flu/RSV plus test included:

• Nasopharyngeal Sample Collection Kit for Viruses

• Copan UTM® 3C057N (Flexible Minitip Flocked Swab with UTM® Medium without Beads)
• Copan eNAT® Molecular Collection and Preservation Medium P/N 6U074S01 (Flexible Minitap Flocked Swab with eNAT® Medium)

• Nasal Sample Collection Kit for Viruses

• Copan UTM® 3C064N (Regular Flocked Swab with UTM® Medium without Beads)
• Copan eNAT® Molecular Collection and Preservation Medium P/N 6U073S01 (Regular Flocked Swab with eNAT® Medium)

• Alternatively, swabs and transport media can be obtained separately:

• Nylon flocked swab (Copan P/N 502CS01, 503CS01)
• Viral Transport Medium, 3 mL (Copan P/N 330C, 3C047N, BD Universal Transport Medium, Remel M4RT, or Remel M5)

The ancillary reagents allow NPS and NS specimens from patients to be collected, preserved and transported to laboratory prior to analysis with the Xpert Xpress CoV 2/Flu/RSV plus test.

Based on the provided FDA 510(k) clearance letter and summary, here's an analysis of the acceptance criteria and study that proves the device meets them:

Important Note: This document describes a "Special 510(k) submission." This type of submission is used when changes are made to a previously cleared device that do not affect its fundamental technology, intended use, or safety/effectiveness. In this specific case, the changes were to the Assay Definition File (ADF) – essentially software parameter settings. Therefore, the "study that proves the device meets the acceptance criteria" largely relies on re-analysis of existing studies from the original device clearance (K242071) rather than entirely new, large-scale clinical trials.

1. Table of Acceptance Criteria and Reported Device Performance

The provided document doesn't explicitly state quantitative acceptance criteria in a dedicated table. However, since this is a Special 510(k) for software parameter changes, the primary "acceptance criteria" appear to be demonstrating non-inferiority or equivalency to the previously cleared predicate device in terms of:

• Valid Test Runs: The number of tests that yield a valid result.
• Non-Determinate (ND) Test Results: The number of tests that do not yield a definitive positive or negative result (e.g., "NO RESULT").
• Performance Claims: That the modifications did not negatively impact the overall analytical and clinical performance claims established for the predicate device (sensitivity, specificity for detecting SARS-CoV-2, Flu A, Flu B, and RSV).

Inferred Acceptance Criteria and Reported Performance:

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

• Sample Size:
  • Main analysis: 16,264 test results. This number represents the re-analysis of "verification, validation and flex studies data from the original studies."
  • SARS-CoV-2 only test mode analysis: 25 test results.
  • Simulated conditions for revised algorithm: The document mentions "Test cartridges were simulated to generate SARS-CoV-2 INVALID and SPC FAIL conditions," but does not explicitly state the number of simulated tests.
• Data Provenance: The data used for re-analysis originated from the "original studies" (K242071 submission). The document does not specify the country of origin or whether these original studies were retrospective or prospective, though typical clinical validation studies for IVDs are often prospective. Given it references "flex study," those can sometimes include both retrospective and prospective elements.

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

The document does not provide information on the number or qualifications of experts used to establish the ground truth. This is likely because the ground truth was established during the original predicate device clearance (K242071) and this Special 510(k) focused on demonstrating equivalence in specific software-related metrics through re-analysis. For IVD devices like this, ground truth is typically established by comparing against a highly sensitive and specific reference method (e.g., an FDA-cleared laboratory developed test or a combination of clinical diagnosis and other accepted testing methods).

4. Adjudication Method for the Test Set

The document does not specify any adjudication method (e.g., 2+1, 3+1, none) for the test set. Again, this specific submission involved re-analysis of existing data rather than new clinical trials where such adjudication might be more explicitly detailed if human reads were involved. For an automated RT-PCR test, adjudication as typically understood for image-based AI would not be directly applicable.

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

No, a Multi-Reader Multi-Case (MRMC) comparative effectiveness study was not conducted or is not mentioned in this document. This is an in vitro diagnostic device (RT-PCR test), not an AI-assisted diagnostic imaging system that would typically involve human readers interpreting images with or without AI assistance. The device is fully automated.

6. Standalone Performance (Algorithm Only)

Yes, the performance evaluated here is inherently standalone (algorithm only). The Xpert Xpress CoV-2/Flu/RSV plus is an automated RT-PCR test system. Its output is directly generated by the instrument and its embedded software (ADF). The "performance data" detailed in section 18.5 describes how the device's algorithmic and software changes affected its ability to produce valid results and interpret them correctly, without human intervention in the result generation.

7. Type of Ground Truth Used

The document does not explicitly state the type of ground truth used for the original studies, beyond stating "analytical, clinical and flex studies data." For RT-PCR assays, the ground truth for clinical performance is typically established by:

• Clinical Reference Method: Comparison against a highly sensitive and specific laboratory reference method (e.g., another FDA-cleared or EUA-authorized RT-PCR test, or a composite reference standard using multiple methods).
• Clinical Diagnosis/Outcomes Data (less common for purely diagnostic tests): While the device aids in diagnosis ("aids in the diagnosis of COVID-19, influenza and/or RSV infections if used in conjunction with other clinical and epidemiological information, and laboratory findings"), the performance claims themselves are based on detection of viral RNA, rather than patient outcomes as primary ground truth.

Given the nature of a molecular diagnostic test for viral RNA, the ground truth for the performance claims (sensitivity, specificity) of the original device would have been established by comparing the device's results against a highly reliable reference molecular test, often considered the "gold standard" for pathogen detection.

8. Sample Size for the Training Set

The document does not provide information on the sample size for the training set. This is because:

• This is an RT-PCR test, not a deep learning AI model that undergoes "training" in the typical machine learning sense. The "algorithm" here refers to the pre-defined logical rules and parameters within the Assay Definition File (ADF) for interpreting RT-PCR signals.
• The re-analysis was performed on verification, validation, and flex studies data, which are typically considered test or validation sets in the context of device development, not training sets.

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

As noted above, a "training set" and associated ground truth establishment in the context of deep learning AI are not applicable to this RT-PCR device. The "ground truth" for the device's performance relies on the known characteristics of the viral targets and the performance of the RT-PCR chemistry against reference methods.

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