Search Results

The cobas® Respiratory 4-flex for use on the cobas® 5800/6800/8800 Systems is an automated, multiplex, nucleic acid test that utilizes real-time polymerase chain reaction (PCR) technology intended for simultaneous in vitro qualitative detection and differentiation of severe acute respiratory syndrome coronavirus (SARS-CoV-2), influenza A virus, influenza B virus, and respiratory syncytial virus (RSV) in nasopharyngeal swab specimens obtained from individuals with signs and symptoms of respiratory tract infection. Clinical signs and symptoms of respiratory viral infection due to SARS-CoV-2, influenza A, influenza B and RSV can be similar. This test is intended to aid in the differential diagnosis of SARS-CoV-2, influenza A, influenza 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 nasopharyngeal swab specimens during the acute phase of infection. The detection and identification of specific viral nucleic acids from individuals exhibiting signs and symptoms of respiratory tract infection are indicative of the presence of the identified virus, and aid 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. Negative results do not preclude SARS-CoV-2, influenza A virus, influenza B virus, or RSV infections. Conversely, positive results do not rule out coinfection with other organisms, and the agent(s) detected by the cobas® Respiratory 4-flex for use on the cobas® 5800/6800/8800 Systems may not be the definite cause of disease.

cobas® Respiratory 4-flex for use on the cobas® 5800/6800/8800 Systems (cobas® Respiratory 4-flex) is based on fully automated sample preparation (nucleic acid extraction and purification) followed by PCR amplification and detection. The cobas® 5800 System is designed as one integrated instrument. The cobas® 6800/8800 Systems consist of the sample supply module, the transfer module, the processing module, and the analytic module. Automated data management is performed by the cobas® 5800 System or cobas® 6800/8800 Systems software(s), which assigns results for all tests. Results can be reviewed directly on the system screen and printed as a report.

Nucleic acid from patient samples and added Internal Control RNA (RNA IC) molecules are simultaneously extracted. Nucleic acid is released by addition of proteinase and lysis reagent to the sample. The released nucleic acid binds to the silica surface of the added magnetic glass particles. Unbound substances and impurities, such as denatured protein, cellular debris and potential PCR inhibitors, are removed with subsequent wash steps and purified nucleic acid is eluted from the magnetic glass particles with elution buffer at elevated temperature. External controls (positive and negative) are processed in the same way.

Selective amplification of target nucleic acid from the sample is achieved by the use of target-specific forward and reverse primers detecting conserved viral genome regions as shown in Table 1.

Selective amplification of RNA IC is achieved by the use of non-competitive, sequence specific forward and reverse primers, which have no homology with the viral-target specific genomes. Amplified target is detected by the cleavage of fluorescently labeled oligonucleotide probes. Roche's temperature assisted generation of signal (TAGS) technology, short TAGS technology, is introduced to differentiate up to three targets per fluorescence channel, enabling the detection of up to14 targets, and the Internal Control, per well. A thermostable DNA polymerase enzyme is used for amplification.

Multiplicity of target detection is enabled with temperature-dependent quenching of cleaved fluorescent target-specific probes. This is achieved by separating signals from probes into introduced thermal channels, where fluorescence is acquired at two additional fixed temperatures for each amplification cycle.

During the PCR amplification step, hybridization of the probes to the specific single-stranded DNA template results in cleavage of the probe by the 5' to 3' exonuclease activity of the DNA polymerase, resulting in separation of the reporter and quencher dyes, and the generation of a fluorescent signal. Conventional probes release fluorescence signal immediately upon separation of reporter from quencher. TAGS probes rely on temperature dependent fluorescence activation, requiring both nuclease cleavage during the extension phase, as well as an increase in reaction temperature, to activate the otherwise dormant fluorophore. For this reason, during each PCR cycle the TAGS technology captures fluorescence in five available fluorescence channels in combination with three thermal channels (detection of fluorescence at three defined temperatures T1, T2 and T3).

The cobas® Respiratory 4-flex master mix contains detection probes which are specific for influenza A virus, influenza B virus, RSV, SARS-CoV-2 and the RNA Internal Control (RNA IC) nucleic acid, which enables simultaneous detection and differentiation of influenza A virus, influenza B virus, RSV, and SARS-CoV-2 viral targets and the RNA IC.

The master mix includes deoxyuridine triphosphate (dUTP), instead of deoxythymidine triphosphate (dTTP), which is incorporated into the newly synthesized DNA (amplicon). Any contaminating amplicons from previous PCR runs are destroyed by the AmpErase enzyme [uracil-N-glycosylase], which is included in the PCR mix, when heated in the first thermal cycling step. However, newly formed amplicons are not destroyed since the AmpErase enzyme is inactivated once exposed to temperatures above 55°C.

The RESP-4FLEX ASAP enables the system to differentiate and report the qualitative results of the four targets influenza A virus, influenza B virus, RSV and SARS-CoV-2. For each specimen the customer can test for any combination of the four enabled virus targets. Also, additional target calculation (digital reflex) can be ordered for the four enabled virus targets (influenza A virus, influenza B virus, RSV and SARS-CoV-2) on the cobas® 5800 System.

Here's an analysis of the acceptance criteria and study detailed in the provided FDA clearance letter for the cobas Respiratory 4-flex, structured according to your request:

1. Table of Acceptance Criteria and Reported Device Performance

The FDA clearance letter does not explicitly state pre-defined acceptance criteria for the clinical performance. Instead, it reports the observed performance metrics (PPA and NPA) from the clinical studies. For the purpose of this table, I will present the reported clinical performance as the "met acceptance criteria," assuming these values were deemed acceptable by the FDA for clearance.

Study Proving Device Meets Criteria: The detailed clinical performance evaluation described in "5. CLINICAL PERFORMANCE EVALUATION" (pages 23-26) demonstrates that the cobas Respiratory 4-flex achieves the reported Positive Percent Agreement (PPA) and Negative Percent Agreement (NPA) values against a U.S. FDA-cleared molecular comparator assay. These reported percentage agreements, along with their 95% confidence intervals, serve as the evidence that the device meets the performance expectations for clinical use.

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

• Prospective Clinical Study:

  • Total NPS specimens enrolled: 4,475
  • Total NPS specimens tested: 4,378 (1,832 fresh, 2,546 frozen)
  • Total NPS specimens evaluable: 4,341 (1,827 fresh, 2,514 frozen)
  • Data Provenance: Fresh prospective specimens collected at eleven collection sites during the 2023-2024 respiratory viral season. Frozen prospective specimens collected during parts of the 2022-2023 respiratory viral season at seven sites and the 2023-2024 respiratory viral season from 14 collection sites. The specific country of origin is not explicitly stated but implies U.S. based on the "U.S. testing sites" mention for retrospective samples, and the FDA clearance context. The data is prospective.

• Retrospective Clinical Study:

  • Total NPS specimens enrolled: 770
  • Total NPS specimens evaluable:
    • Influenza A: 657
    • Influenza B: 647
    • RSV: 659
  • Data Provenance: Archived NPS specimens collected between 2014 and 2022 from individuals with signs and symptoms of respiratory viral infection. Tested at three (3) U.S. testing sites. The data is retrospective.

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

The document does not mention the use of human experts to establish ground truth for the test set. The ground truth was established by a "U.S. FDA-cleared molecular assay" as the comparator method.

4. Adjudication Method for the Test Set

The document does not describe an adjudication method involving experts for discrepant results. Instead, it states that an "FDA 510(k) cleared comparator" method was used to establish the "ground truth." For the influenza A target in the prospective study, "three (3) additional specimens (two (2) fresh and one (1) frozen) were excluded from analysis due to inconclusive results obtained from the comparator test," implying a reliance on the comparator's definitive result rather than external adjudication. The same pattern is noted for retrospective samples, with exclusions for failed or invalid comparator test results.

5. If a Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study Was Done, and the Effect Size of Human Readers' Improvement with AI vs. Without AI Assistance

This section is Not Applicable to the provided document. The cobas Respiratory 4-flex is an automated, multiplex nucleic acid detection test, not an AI-powered diagnostic tool requiring human reader interpretation or assistance. Therefore, an MRMC study or analysis of human reader improvement with AI is not relevant.

6. If a Standalone (i.e., Algorithm Only Without Human-in-the-Loop Performance) Was Done

Yes, this was a standalone performance evaluation. The device is an automated in vitro diagnostic (IVD) test. The clinical performance evaluation directly compares the cobas Respiratory 4-flex's results (algorithm only, as it's an automated system) against a predicate FDA-cleared molecular assay. There is no human interpretation or intervention in the generation of the primary test result from the cobas system itself.

7. The Type of Ground Truth Used (Expert Consensus, Pathology, Outcomes Data, etc.)

The ground truth for the clinical performance evaluation was established by a "U.S. FDA-cleared molecular assay." This means another legally marketed and validated molecular diagnostic test was used as the reference standard.

8. The Sample Size for the Training Set

The document does not specify a separate training set or its sample size. This is typical for in vitro diagnostic (IVD) devices that use established laboratory techniques (like PCR) rather than machine learning algorithms which require explicit training data. The development of such assays involves extensive analytical validation (LoD, precision, specificity, inclusivity, etc.) and then clinical validation with independent samples.

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

Since no explicit training set for a machine learning algorithm is mentioned, the concept of "ground truth for the training set" is not applicable in the context of this device's validation as described. The analytical studies (LoD, inclusivity, specificity, etc.) characterize the inherent performance of the assay's chemical and hardware components.

Ask a specific question about this device