(326 days)
The AxSYM Toxo IgM assay is a Microparticle Enzyme Immunoassay (MEIA) for the qualitative measurement of IgM antibodies to Toxoplasma gondii in human serum and plasma (EDTA, heparin, or sodium citrate) to aid in the diagnosis of primary infection. The AxSYM Toxo IgM assay is not for use with cord blood or neonatal specimens. This product is not FDA cleared for use in testing blood or plasma donors.
The AxSYM Toxo IgM assay is a Microparticle Enzyme Immunoassay (MEIA) for the qualitative measurement of IgM antibodies to Toxoplasma gondii in human serum and plasma (EDTA, heparin, or sodium citrate). It utilizes polystyrene microparticles coated with Toxoplasma gondii antigen and a conjugate containing goat anti-human IgM antibody conjugated to alkaline phosphatase. The assay is performed on an automated instrument and utilizes a rheumatoid neutralization buffer.
Here's an analysis of the provided text, outlining the acceptance criteria and the study used to demonstrate the device meets them:
1. Table of Acceptance Criteria and Reported Device Performance
| Acceptance Criterion | Device Performance (AxSYM Toxo IgM assay) |
|---|---|
| Relative Sensitivity | 96.3% |
| Relative Specificity | 99.8% |
| Relative Agreement | 99.3% |
| Percent CV (positive panel members/control) | 6.0% to 10.1% |
Note: The document does not explicitly state pre-defined acceptance criteria values for these metrics. Instead, it presents the device's performance as evidence of substantial equivalence to the predicate device. The implied acceptance is that these performance metrics are comparable or superior to the predicate.
2. Sample Size and Data Provenance
- Test Set Sample Size: 1,400 samples
- Data Provenance:
- Country of Origin: Two U.S. sites and one European site.
- Retrospective/Prospective: The document does not explicitly state whether the study was retrospective or prospective. Given the comparison to a legally marketed device and sample collection from specific populations (pregnant women, non-pregnant individuals, and individuals positive for IgM antibodies to T. gondii), it is likely a combination or a retrospective analysis of collected samples.
3. Number of Experts and Qualifications for Ground Truth
- The document does not specify the number of experts used to establish the ground truth for the primary comparison.
- The ground truth for discordant results was established by re-testing with two other legally marketed devices (Platelia Toxo IgM and Abbott IMx Toxo IgM Antibody assay). This implies the "experts" in this context are the established performance and results of these reference assays, rather than human experts directly.
4. Adjudication Method for the Test Set
- Discordant Resolution: Discordant results between the AxSYM Toxo IgM assay and the VIDAS Toxo IgM assay were resolved by testing with two additional legally marketed devices: Platelia Toxo IgM (Sanofi) and Abbott IMx Toxo IgM Antibody assay. This is a form of "reference method adjudication" using other commercial assays as the adjudicators.
5. Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study
- No, an MRMC comparative effectiveness study was not done. This study solely focuses on comparing the performance of the AxSYM Toxo IgM assay to a predicate device (VIDAS Toxo IgM assay). It does not involve human readers or assess the improvement of human readers with or without AI assistance, as it is a diagnostic laboratory assay, not an AI-assisted diagnostic tool for interpretation.
6. Standalone Performance
- Yes, a standalone performance study was done. The reported performance metrics (relative sensitivity, specificity, and agreement) are for the AxSYM Toxo IgM assay itself when compared against the predicate device and the reference methods used for discordant resolution. This represents the algorithm's (assay's) performance without human intervention in the result determination beyond running the assay.
7. Type of Ground Truth Used
- The primary "ground truth" was established by comparison to a predicate device (bioMerieux VIDAS Toxo-M).
- For discordant results, the ground truth was further established by agreement with two other legally marketed reference assays (Platelia Toxo IgM and Abbott IMx Toxo IgM Antibody assay). This can be considered a form of "reference assay consensus" or "established test outcome."
8. Sample Size for the Training Set
- The document does not specify a training set sample size. This is common for this type of in vitro diagnostic device (IVD) submission, as it describes a comparative study for substantial equivalence, not the development and training of a novel algorithm in the AI sense. The study focuses on validation of the assay's performance rather than algorithmic training.
9. How Ground Truth for the Training Set Was Established
- Since there's no mention of a dedicated "training set" in the context of an AI algorithm, details on how its ground truth was established are not applicable and not provided in this document. The study is a performance validation against a predicate, implying the predicate itself represents the established clinical utility or "ground truth" for the comparison.
§ 866.3780
Toxoplasma gondii serological reagents.(a)
Identification. Toxoplasma gondii serological reagents are devices that consist of antigens and antisera used in serological tests to identify antibodies toToxoplasma gondii in serum. Additionally, some of these reagents consist of antisera conjugated with a fluorescent dye (immunofluorescent reagents) used to identifyToxoplasma gondii from clinical specimens. The identification aids in the diagnosis of toxoplasmosis caused by the parasitic protozoanToxoplasma gondii and provides epidemiological information on this disease. Congenital toxoplasmosis is characterized by lesions of the central nervous system, which if undetected and untreated may lead to brain defects, blindness, and death of an unborn fetus. The disease is characterized in children by inflammation of the brain and spinal cord.(b)
Classification. Class II (performance standards).