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IMMULITE Rubella Quantitative is a solid-phase chemiluminescent enzyme immunoassay for use on the IMMULITE Automated Analyzer and designed for the quantitative measurement of IgG antibodies to rubella virus in human serum. It is intended strictly for in vitro diagnostic use as an aid in the determination of immune status to rubella, particularly for women of childbearing age. The performance characteristics of the assay have not been established for use with neonate and cord blood specimens.

IMMULITE® Rubella Quantitative IgG is a solid-phase, two-step, chemiluminescent enzyme unmunoassay. The solid phase, a polystyrene bead enclosed within an IMMULITE Test Unit, is cated with a partially purified rubella antigen. Prediluted patient sample (1-in-21 dilution) and a protein-based buffer are simultaneously introduced into the Test Unit, and incubated for approximately 30 minutes at 37℃ with intermittent agitation. During this time, rubella IgG in the sample binds to the rubella antigencoated bead. Unbound serum is then removed by a centrifugal wash. An alkaline phosphatase-labeled anti-human IgG antibody is introduced, and the Test Unit is Incubated for another 30-minute cycle. The unbound enzyme conjugate is removed by a centrifugal wash. Substrate is then added, and the Test Unit is incubated for an additional 10 minutes. The chemiluminescent substrate, a phosphate ester of adamantyl dioxetane, undergoes hydrolysis in the presence of alkaline phosphatase to vield an unstable intermediate. The continuous production of this intermediate results in the sustained emission of light, thus improving precision by providing a window for multiple reading. The bound complex - and thus the photon output, as measured by the luminometer - is proportional to the presence of rubella IgG in the sample A quantitative result is then obtained by interpolating the adjusted signal response in the master curve.

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Acceptance Criteria and Device Performance Study for IMMULITE Rubella Quantitative IgG

1. Table of Acceptance Criteria and Reported Device Performance

The submission compares the IMMULITE Rubella Quantitative IgG to two benchmarks: a rubella proficiency panel from the United States CDC and the predicate device, Abbott Laboratories' IMx Rubella IgG. The study implicitly sets the performance of these benchmarks as its acceptance criteria for agreement, sensitivity, and specificity.

Note on Acceptance Criteria: The document does not explicitly state numerical acceptance criteria a priori. Instead, it presents performance relative to established methods (CDC panel and predicate device). The implied acceptance is that the device performs "as well as, or better, than the current legally marketed devices."

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

• Test Set 1 (vs. CDC):
  • Sample Size: n=100
  • Data Provenance: The rubella proficiency panel was "obtained from the United States Centers for Disease Control and Prevention (CDC)." This suggests the data is retrospective and originates from the US.
• Test Set 2 (vs. IMx - Study 1):
  • Sample Size: n=217
  • Data Provenance: Not explicitly stated, but likely from a clinical sample collected for method comparison, potentially retrospective or prospective, and likely from the US given the manufacturer's location.
• Test Set 3 (vs. IMx - Study 2):
  • Sample Size: n=200
  • Data Provenance: Not explicitly stated, but likely from a clinical sample collected for method comparison, potentially retrospective or prospective, and likely from the US given the manufacturer's location.
• Linear Regression Analysis:
  • Sample Size: 322 samples (with rubella IgG antibody measurements less than 100 IU/mL). This data overlaps with the IMx comparison studies.
  • Data Provenance: Not explicitly stated, but likely from the same clinical samples used for the IMx comparison, and therefore likely from the US.

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

The document does not specify the number or qualifications of experts used to establish ground truth.

• For the comparison against the CDC proficiency panel, the CDC itself is considered the source of "ground truth" for those reference samples. The method by which the CDC establishes the definitive status of its panel samples is not detailed here.
• For comparisons against the IMx assay, the IMx assay itself is treated as the reference standard (predicate device). The "ground truth" is established by the IMx result.

4. Adjudication Method for the Test Set

The document does not specify any adjudication method for establishing ground truth for the test set. For the CDC panel, it's presumed the CDC provides definitive results. For the IMx comparisons, the IMMULITE results are directly compared to the IMx results, implying the IMx result acts as the single reference standard for each sample.

5. If a Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study was done, and the effect size of human readers with/without AI assistance

This is not applicable as the device is an automated immunoassay analyzer, not an AI-assisted diagnostic imaging or classification system that involves human readers interpreting results with or without AI assistance. It's a laboratory diagnostic test.

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

Yes, the studies presented are standalone performance studies of the IMMULITE Rubella Quantitative IgG device. The device autonomously measures rubella IgG antibodies and provides a quantitative result. Its performance is evaluated directly against reference methods (CDC panel, IMx assay) without explicit human interpretation being part of the performance metric reported for the device itself. The "human-in-the-loop" here is the lab technologist performing the test and reporting the result, not interpreting complex visual data.

7. The Type of Ground Truth Used

• For the CDC comparison: The ground truth is established by the rubella proficiency panel obtained from the United States Centers for Disease Control and Prevention (CDC). This implies established, verified reference values for rubella IgG status.
• For the IMx comparisons: The ground truth is established by the results obtained from the Abbott Laboratories IMx® Rubella IgG kit, which is the predicate device. This is a form of comparative ground truth against an established, legally marketed assay.

8. The Sample Size for the Training Set

The document does not specify the sample size for any training set. As this is a 510(k) submission for a traditional immunoassay, not a machine learning or AI device, the concept of a "training set" in the context of model development (as might be discussed for AI) is not directly relevant or reported in this type of submission. The performance assessment focuses on validation against known samples and predicate devices.

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

As noted above, a "training set" in the AI/ML sense is not an applicable concept for this immunoassay device's submission. Therefore, the method for establishing ground truth for a non-existent explicit training set is not applicable and not mentioned in the document.

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