(269 days)
IMMULITE Toxoplasma Quantitative IgG is designed for the quantitative detection of IgG antibodies to Toxoplasma gondii in human serum and is intended strictly for in vitro diagnostic use as an aid in the determination of serological status to Toxoplasma gondii.
IMMULITE® Toxoplasma Quantitative IgG is a solid-phase, two-step, chemiluminescent enzyme immunoassay. The solid phase, a polystyrene bead enclosed within an IMMULITE® Test Unit, is coated with a partially purified Toxoplasma gondii antigen, strain RH. 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°C with intermittent agitation. During this time, toxoplasma IgG in the sample binds to the toxoplasma antigen-coated 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 yield 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 readings. The bound complex - and thus the photon output, as measured by the luminometer - is directly related to the quantity of toxoplasma IgG in the sample. A quantitative result in IU/mL is then obtained by comparing the patient result to a stored Master Curve, and which is adjusted to the response of each analyzer.
Here's a breakdown of the acceptance criteria and the study proving the device meets them, based on the provided text:
Acceptance Criteria and Device Performance
| Acceptance Criteria | Reported Device Performance (IMMULITE vs. VIDAS®) | Reported Device Performance (IMMULITE vs. IMx®) |
|---|---|---|
| Agreement (Overall) | 99.0% | 96.4% |
| Sensitivity (Positive Agreement) | 96.3% | 90.2% |
| Specificity (Negative Agreement) | 100.0% | 98.6% |
Study Details
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Sample size used for the test set and the data provenance:
- Test Set Sample Size: 199 serum specimens for the comparison with VIDAS®, and 194 serum specimens for the comparison with IMx®.
- Data Provenance: Not explicitly stated, but the mention of "serum specimens" implies clinical samples. The country of origin and whether they were retrospective or prospective are not mentioned.
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Number of experts used to establish the ground truth for the test set and the qualifications of those experts:
- The document describes a comparison study against predicate devices (VIDAS® and IMx® Toxoplasma IgG assays) rather than establishing a de novo ground truth with experts. Therefore, the "ground truth" for the IMMULITE device's performance is the results obtained from these established predicate devices. No external experts are mentioned as establishing a ground truth.
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Adjudication method (e.g. 2+1, 3+1, none) for the test set:
- No adjudication method is mentioned. The study directly compared IMMULITE results with those from the predicate devices.
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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. This is an in-vitro diagnostic device (immunoassay) for detecting antibodies in serum, not an imaging device requiring human reader interpretation or AI assistance. An MRMC study is not applicable.
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If a standalone (i.e. algorithm only without human-in-the-loop performance) was done:
- Yes, this device is a standalone automated immunoassay analyzer. The performance metrics presented (Agreement, Sensitivity, Specificity) represent the performance of the IMMULITE system itself, without human interpretation of the final quantitative result.
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The type of ground truth used (expert consensus, pathology, outcomes data, etc):
- The ground truth was established by two commercially available and legally marketed predicate devices: bioMerieux Vitek VIDAS® Toxo IgG and Abbott Laboratories IMx® Toxo IgG. The performance of IMMULITE was compared to these established assays.
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The sample size for the training set:
- The document does not mention a "training set" in the context of machine learning. For an immunoassay, the "training" typically refers to the development and optimization of the assay itself and the establishment of manufacturing controls and calibration procedures, not a separate data set for algorithm training.
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How the ground truth for the training set was established:
- As mentioned above, the concept of a "training set" with ground truth in the machine learning sense is not applicable to this type of immunoassay device. The assay development would involve internal validation and standardization processes.
§ 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).