Search Results

The Accula RSV Test performed on the Accula Dock is a molecular in vitro diagnostic test utilizing polymerase chain reaction (PCR) and lateral flow technologies for the qualitative, visual detection of respiratory syncytial virus (RSV) viral RNA. The Accula RSV Test uses a nasal swab specimen collected from patients with signs and symptoms of respiratory infection. The Accula RSV Test is intended as an aid in the diagnosis of RSV infection in children and adults in conjunction with clinical and epidemiological risk factors.

Negative results do not preclude RSV virus infection and should not be used as the sole basis for treatment or other patient management decisions.

The Accula RSV Test is a semi-automated, colorimetric, multiplex reverse-transcription polymerase chain reaction (RT-PCR) nucleic acid amplification test to qualitatively detect respiratory syncytial virus (RSV) viral RNA from unprocessed nasal swabs that have not undergone prior nucleic acid extraction. The system integrates nucleic acid extraction, reverse transcription, a novel Mesa Biotech PCR nucleic acid amplification technology named OscARTM, and hybridization-based visual detection into a completely self-contained and automated system. The Accula RSV system consists of a small reusable Dock to drive the automated testing process, and a single-use disposable test cassette that contains all the enzymes and reagents.

Accula RSV Test - Acceptance Criteria and Performance Study Analysis

This document outlines the acceptance criteria and the performance of the Accula RSV Test based on the provided 510(k) summary (K181443).

1. Table of Acceptance Criteria and Reported Device Performance

The 510(k) summary primarily focuses on clinical performance characteristics and analytical performance rather than explicitly stating pre-defined "acceptance criteria" numerical targets in the same way a device specification might. However, based on the studies conducted, the implicit acceptance criteria are that the device demonstrates comparable or superior performance to the FDA-cleared predicate device and meets predefined thresholds for analytical validity.

Here's a summary of the observed performance:

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

• Clinical Performance Test Set:

  • Sample Size: 694 evaluable specimens (out of 749 subjects enrolled).
  • Data Provenance: Prospective clinical study conducted in the U.S. during the 2017-2018 RSV season. Specimens were collected from patients presenting at ten investigational sites with RSV-like symptoms.

• Reproducibility Test Set:

  • Sample Size: For each sample type (RSV Negative, RSV Low Positive, RSV Moderate Positive), there were 30 observations per site (2 operators x 1 run x 3 swabs x 5 non-consecutive days). With 4 sites, this totals approximately 120 observations per sample type.
  • Data Provenance: Contrived nasal swabs tested at three CLIA-waived sites and one moderately complex site based in the United States.

• Limit of Detection Test Set:

  • Sample Size: 20 replicates for each virus strain and concentration tested.
  • Data Provenance: Contrived samples prepared by spiking RSV strains into a pooled negative clinical matrix.

• Analytical Reactivity Test Set:

  • Sample Size: 3 replicates for each of the 9 RSV strains.
  • Data Provenance: Contrived samples prepared by diluting virus in pooled clinical matrix and spiking onto a swab.

• Analytical Specificity Test Set:

  • Sample Size: 3 replicates for each of the 41 potentially cross-reacting organisms.
  • Data Provenance: Contrived samples prepared by diluting organisms in a clinical matrix.

• Interfering Substances Test Set:

  • Sample Size: 3 replicates for two RSV strains (RSV A2, RSV B1) with each of the 13 interfering substances, plus negative controls.
  • Data Provenance: Contrived samples with virus diluted into pooled negative clinical matrix and interfering substances added.

• Near-Cutoff Study Test Set (CLIA Waiver):

  • Sample Size: 60 samples per site (30 replicates of RSV Low Positive, 30 replicates of True Negative). With 3 sites, total of 180 samples.
  • Data Provenance: Contrived samples (RSV Low Positive spiked into negative clinical matrix; True Negative from negative clinical matrix with no RSV virus) handled by untrained intended operators at three CLIA-waived sites in the U.S.

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

The 510(k) summary does not explicitly state the number or specific qualifications of experts used to establish the ground truth.

For the primary clinical performance comparison, the ground truth was established by:

• A FDA-cleared molecular RSV assay as the initial comparator method.
• An alternative FDA-cleared molecular RSV assay used to resolve all discrepant results (e.g., false positives and false negatives from the initial comparison).

This approach relies on the established accuracy of commercially available and FDA-cleared molecular assays as the "expert" or gold standard for diagnostic truth.

4. Adjudication Method for the Test Set

For the prospective clinical study:

• The Accula RSV Test results were compared to a primary FDA-cleared molecular comparator.
• All discrepant results between the Accula RSV Test and the primary comparator were adjudicated using an alternative FDA-cleared molecular RSV assay at a reference laboratory. This serves as a 2+1 adjudication method, where the two molecular assays determine the final truth.

5. If a Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study Was Done, If So, What Was the Effect Size of How Much Human Readers Improve with AI vs. Without AI Assistance

No, a Multi-Reader Multi-Case (MRMC) comparative effectiveness study was not done.

This device, the Accula RSV Test, is a semi-automated, colorimetric nucleic acid amplification test for the qualitative detection of RSV viral RNA. It is a diagnostic test where the result (presence or absence of colored lines on a test strip) is visually interpreted directly by a human, but the "reading" is of a molecular reaction, not an image requiring nuanced expert interpretation. The provided studies focus on the analytical and clinical accuracy of the device itself and its agreement with established molecular methods, and its reproducibility across different users and sites (including untrained users in the CLIA waiver study). There is no "AI assistance" component to human readers, as the output is a direct visual detection by a human of the test strip post-reaction, not an interpretation of complex data or images aided by AI.

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

Yes, the primary clinical and analytical performance studies can be considered standalone performance for the device's diagnostic capability.

While the final interpretation of the colored lines is visual (human-in-the-loop for reading the result), the underlying molecular amplification and detection mechanism (OscAR™ technology, hybridization-based visual detection) operates as a standalone algorithm/system to determine the presence or absence of RSV RNA. The "Performance Near the Cut-off" study with untrained users further investigates the robustness of this standalone performance even when subjected to diverse human operation, demonstrating that the device consistently performs at the Limit of Detection. The analytical studies (LoD, inclusivity, cross-reactivity, interfering substances) also represent standalone performance of the test's ability to detect or not detect specific targets under controlled conditions.

7. The Type of Ground Truth Used

The ground truth for the clinical performance evaluation was established using FDA-cleared molecular RSV assays. Specifically:

• An initial FDA-cleared molecular RSV assay as the primary comparator.
• An alternative FDA-cleared molecular RSV assay for adjudication of discrepant results.

For analytical studies (LoD, inclusivity, cross-reactivity, interfering substances, reproducibility, near-cutoff), the ground truth was based on known spiked concentrations of purified RSV virus strains or other organisms in a negative clinical matrix.

8. The Sample Size for the Training Set

The 510(k) summary does not explicitly describe a separate "training set" in the context of machine learning model development. This is typical for traditional in vitro diagnostic devices like the Accula RSV Test, which rely on established biochemical and molecular principles rather than AI/ML algorithms that require large training datasets.

The development and optimization of the Accula RSV Test (e.g., reagent concentrations, reaction conditions, LoD determination) would have involved extensive laboratory experimentation and optimization, which could be conceptually seen as internal "training" or development phases, but these are not datasets reported in the same way as a machine learning training set for regulatory submission.

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

As noted above, a distinct "training set" for an AI/ML model is not described in this 510(k) summary. The ground truth for the analytical and clinical validation studies (which support the device's claims) was established as described in section 7:

• For clinical performance: FDA-cleared molecular RSV assays.
• For analytical performance: known spiked concentrations of purified virus/organisms.

Ask a specific question about this device