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The LIAISON® Toxo IgM II assay uses chemiluminescent immunoassay (CLIA) technology on the LIAISON® XL Analyzer for the qualitative determination of IgM antibodies to Toxoplasma gondii in human serum samples. It is intended for use as an aid in the presumptive diagnosis of acute or recent Toxoplasma gondii infection, including pregnant women. It is recommended that the LIAISON® Toxo IgM II assay be performed in conjunction with a Toxoplasma gondii IgG assay. This assay has not been cleared/approved by the FDA for blood/plasma donor screening.

The LIAISON Control Toxo IgM II (negative and positive) is intended for use as assayed quality control samples to monitor the performance of the LIAISON Toxo IgM II assay on the LIAISON® XL Analyzer.

The method for qualitative determination of specific IgM to Toxoplasma gondii is an antibody capture chemiluminescence immunoassay (CLIA). The principal components of the test are magnetic particles (solid phase) coated with IgG (mouse, monoclonal) is used for coating magnetic particles (solid phase) and a mouse monoclonal antibody to human IgM, Toxoplasma gondii antigen, and a conjugate of mouse monoclonal antibodies to Toxoplasma gondii linked to an isoluminol derivative (isoluminol-antibody coniugate).

During the first incubation, IgM antibodies present in calibrators, samples or controls bind to the solid phase. During the second incubation, the mouse monoclonal antibody conjugate reacts with Toxoplasma gondii antigen and the immune complex thus formed reacts with IgM already bound to the solid phase. After the incubations, 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) and is indicative of Toxoplasma gondii IgM concentration present in calibrators, samples or controls.

All assay steps and incubations are performed by the LIAISON® XL Analyzer.

The provided text describes the LIAISON® Toxo IgM II assay, a chemiluminescent immunoassay (CLIA) for the qualitative determination of IgM antibodies to Toxoplasma gondii. Here's a breakdown of the acceptance criteria and the studies performed:

1. Table of Acceptance Criteria and Reported Device Performance

The acceptance criteria for the LIAISON® Toxo IgM II assay are primarily demonstrated through comparative clinical studies, particularly in terms of agreement with a comparator assay and a CDC panel. The document doesn't explicitly state numerical acceptance criteria thresholds (e.g., "must achieve X% sensitivity"), but rather presents the achieved performance. Based on the data provided, implied criteria are high agreement percentages for both negative and positive samples.

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

• Prospective US Population: 204 individuals. Data provenance: US, prospective.
• Prospective European Population: 600 individuals. Data provenance: European, prospective.
• Pregnant Women Population: 201 females. Data provenance: Not specified (likely US or European as part of prospective studies), prospective.
• Retrospective/Pre-Selected Population: 33 samples. Data provenance: Not specified (likely US or European), retrospective.
• CDC Panel Study: 100 frozen blind specimens (32 true positive, 65 true negative, 3 dilutions of 3 true positive samples). Data provenance: CDC (reference panel), retrospective.
• Precision and Reproducibility:
  • Precision study: 80 measurements per sample (one site).
  • Reproducibility study: 480 measurements per sample (three sites).

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

The document does not specify the number or qualifications of experts used to establish the ground truth for the clinical study test sets. It mentions a "comparator assay" and "references" for the CDC panel, implying established methods or expert determinations, but details are not provided.

4. Adjudication Method for the Test Set

The document does not describe any specific adjudication method (e.g., 2+1, 3+1) for the clinical study test sets. The "comparator assay" served as the basis for classification in the prospective and retrospective studies. For the CDC panel, the CDC itself provided the "true positive" and "true negative" categorizations.

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

No, a multi-reader multi-case (MRMC) comparative effectiveness study was not conducted. This device is a diagnostic assay (an in-vitro diagnostic, IVD), not an image-based AI device designed for human reader assistance. Therefore, the concept of human readers improving with or without AI assistance does not apply.

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

Yes, the performance studies for the LIAISON® Toxo IgM II assay were conducted in a standalone manner. The assay, which is an automated chemiluminescent immunoassay, directly measures and reports results (qualitative determination of IgM antibodies) without human intervention in the interpretation process of the assay's output itself. The results are generated by the LIAISON® XL Analyzer.

7. The Type of Ground Truth Used

• Clinical Studies (Prospective and Retrospective): The ground truth was established by a "comparator assay" (Diamedix Is-Toxoplasma IgM Capture Test System (K001707)).
• CDC Panel Study: The ground truth was established by the "CDC (Reference Immunodiagnostic Lab, Biology and Diagnostic Branch Division of Parasitic Diseases)" which categorized samples as "Toxoplasma IgM true positive" and "Toxoplasma IgM true negative." This represents a form of expert consensus and reference laboratory determination.

8. The Sample Size for the Training Set

The document does not explicitly mention a "training set" for an algorithm, as this is an IVD assay, not a machine learning model in the typical sense. The assay is built on established biochemical principles and reagents. Therefore, the concept of a training set for an AI/algorithm is not directly applicable. If one were to interpret "training" in the context of assay development, it would refer to the optimization and validation experiments conducted during the assay's development prior to the reported clinical studies, but no sample sizes for such development phases are provided.

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

Since there is no explicit "training set" for an AI algorithm, this question is not directly applicable. The assay's analytical characteristics and performance are based on its chemical and immunological design, calibrated against reference materials and validated using clinical samples.

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