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The LIAISON® Rubella IgG uses chemiluminescencc immunoussay (CLIA) technology on the LIAISON Analyzer for the qualitative determination of IgG antibodies to rubella virus in human serum specimens. It is intended for use as an aid in the determination of immune status to rubella in individuals including pregnant women.

The performance of this device has not been established for cord blood, neonatal samples, or for any matrices other than human serum. Likewise, performance has not been established for population(s) of immunocompromised or immunosuppressed individuals.

The LIAISON® Rubella IgG Tri-Control kit is intended for use as assayed quality control samples to monitor the performance of the LIAISON® Rubella IgG assay.

The method for qualitative determination of specific IgG to Rubella virus is an indirect chemiluminescence immunoassay (CLIA). All assay steps (with the exception of magnetic particle resuspension) and incubations are performed by the LIAISON® Analyzer. The principal components of the test are magnetic particles (solid phase) coated with Rubella antigen and a conjugate of mouse monoclonal antibody to human IgG linked to an isoluminol derivative (isoluminol-antibody conjugate). During the first incubation, Rubella virus antibodies present in the calibrators, specimens or controls bind to the solid phase. During the second incubation, the antibody conjugate reacts with Rubella virus IgG already bound to the solid phase. After each incubation, the unbound material is removed with a wash cycle. Subsequently, the starter reagents are added and a flash chemiluminescence reaction is thus induced. The light signal, and hence the amount of isoluminol-antibody conjugate, is measured by a photomultiplier as relative light units (RLU).

The provided document describes the DiaSorin LIAISON® Rubella IgG Assay, a chemiluminescence immunoassay (CLIA) for the qualitative determination of IgG antibodies to rubella virus in human serum, intended as an aid in determining immune status, including in pregnant women.

1. Table of Acceptance Criteria and Reported Device Performance

The acceptance criteria are not explicitly stated in numerical thresholds within the provided text. Instead, the document presents comparative study results against a "commercially available rubella chemiluminescence test kit" and consensus testing with three FDA-cleared ELISA devices for equivocal samples, as well as an evaluation using a CDC performance panel. The reported device performance is as follows:

*c: Number of samples too low to reliably calculate % negative agreement for this group.

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

• Comparative Study (Non-selected subjects):
  • Total: 2806 prospectively collected frozen specimens.
  • Routine Rubella IgG Testing: 2159 samples.
  • Pregnant Women: 449 samples.
  • Data Provenance: Prospectively collected specimens from U.S. subjects. The "routine rubella IgG testing" and "pregnant women" samples were part of this overall set. Samples were divided randomly, and testing sites were blinded to populations and comparator results.
• Comparative Study (Pre-selected Negative Subjects):
  • Total: 198 pre-selected negative subjects.
  • Routine Rubella IgG Testing: 98 subjects.
  • Pregnant Women: 100 subjects.
  • Data Provenance: Prospectively collected from U.S. subjects. These were pre-selected based on initial negative results from predicate device testing.
• CDC Performance Panel: 100 specimens (50 pairs of sera, 18 negative, 82 positive).
  • Data Provenance: Obtained from the CDC (Centers for Disease Control and Prevention), a masked, characterized serum panel.

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

The document does not explicitly state the number or specific qualifications (e.g., "radiologist with 10 years of experience") of experts used to establish the ground truth.

For the comparative study, the ground truth was established by:

• "a commercially available rubella chemiluminescence test kit" (predicate device).
• For equivocal samples from the predicate device, a consensus of 2 out of 3 results from three FDA-cleared ELISA devices was used.
• For the pre-selected negative subjects, the initial predicate device testing (rubella antibody testing performed by the laboratories) was used to define samples as negative. For the 100 pregnant women, no equivocal results were found in the initial predicate test, so no consensus was needed for this cohort.

For the CDC Performance Panel, the samples were a "masked, characterized serum panel" with known status (titered by HI), implying the ground truth was established by the CDC through their characterization methods.

4. Adjudication Method for the Test Set

• For equivocal samples from the predicate device: A "2 out of 3 rule using 3 additional FDA cleared assays" was applied. If a sample had concordant results by at least two of the three methods, the consensus defined the result. If discordant or concordant equivocal, the sample remained classified as equivocal.
• For the pre-selected negative subjects: The initial predicate test results were used as the basis for definition (no explicit "adjudication" beyond that initial classification is mentioned in the context of validating the LIAISON device).

5. If a Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study Was Done

No, an MRMC comparative effectiveness study was not done. This device is an in-vitro diagnostic assay that provides an objective measurement (Index value) and qualitative result (Positive, Negative, Equivocal) rather than relying on human interpretation of images or other subjective data. Therefore, the concept of "human readers improve with AI vs. without AI assistance" does not apply.

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

Yes, the studies presented are standalone performance evaluations of the DiaSorin LIAISON® Rubella IgG Assay. The output is a numerical Index and a qualitative classification (Positive, Equivocal, Negative) generated by the automated LIAISON Analyzer based on the chemiluminescence immunoassay technology. There is no human-in-the-loop interpretation that impacts the device's direct output.

7. The Type of Ground Truth Used

• Comparative Studies:
  • Comparator Assay / Predicate Device: A commercially available rubella chemiluminescence test kit.
  • Consensus Testing: For equivocal samples, results from "three FDA cleared devices" (ELISA assays) using a 2 out of 3 rule.
  • Pre-selected Negatives: Initial negative classification by existing laboratory rubella IgG testing.
• CDC Performance Panel: Characterized serum panel with known rubella IgG status, likely established through a combination of serological methods, including HI (Hemagglutination Inhibition).

8. The Sample Size for the Training Set

The document does not explicitly describe a separate "training set" in the context of machine learning or AI development. Since this is an immunoassay, the device's "training" would typically involve optimization and calibration during development using internal panels, but these are not explicitly detailed as a distinct "training set" in a manner typical for AI algorithms in this regulatory submission. All the sample sizes mentioned (2806 for comparative, 100 for CDC) are used for performance evaluation/testing.

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

As no explicit "training set" in the AI sense is provided, the method for establishing its ground truth is not applicable or detailed in this document. The assay's parameters would have been established and optimized during its development using various internal reference materials and panels, but these are not outlined as a formal "training set" with established ground truth in the context of this 510(k) summary.

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