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510(k) Data Aggregation
(53 days)
The Access Toxo IgG assay is a paramagnetic-particle, chemiluminescent immunoassay for the qualitative and quantitative determination of IgG antibodies to Toxoplasma gondii in human serum using the Access Immunoassay Systems. The Access Toxo IgG assay aids in the diagnosis of Toxoplasma gondii infection and may be used to assess the immune status of pregnant women.
Note: In the United States, this product is not FDA cleared/approved for the screening of blood or plasma donors. Assay performance characteristics have not been established for immunocompromised or immunosuppressed patients, cord blood, neonatal specimens or infants.
The Access Toxo IgG Assay, Toxo IgG Calibrators, Toxo IgG QC, and the Access Immunoassay Analyzers (Access, Access 2, Synchron LXi 725, UniCel DxC 600i, UniCel Dxl 600 and UniCel Dxl 800) comprise the Access Immunoassay Systems for the quantitative and qualitative determination of anti- Toxoplasma gondii IgG in human serum.
The Access Toxo IgG Assay is intended for the quantitative and qualitative determination of IgG antibodies to Toxoplasma gondii in human serum. It aids in the diagnosis of Toxoplasma gondii infection and can assess the immune status of pregnant women.
1. Table of Acceptance Criteria and Reported Device Performance:
The document primarily focuses on demonstrating substantial equivalence to predicate devices rather than defining explicit acceptance criteria. However, performance metrics were evaluated in comparison to a predicate device and a CDC panel. The key performance indicators and results are summarized below:
| Performance Metric | Acceptance Criteria (Implied/Predicate-based) | Reported Device Performance |
|---|---|---|
| Analytical Sensitivity (LoQ) | Not explicitly stated as an acceptance criterion, but low detection limit is desirable. | Mean Limit of Quantitation (LoQ) was 3.2 IU/mL. |
| Dilution Recovery (Linearity) | Recovery close to 100% for WHO standards and high patient samples across dilutions. | WHO Standard Recovery: Ranged from 78.1% to 108.5% across five dilutions of the Third International Standard for Anti-Toxoplasma Serum (TOXM). |
| Linearity with High Patient Samples: Mean recovery was 100%, ranging from 93.8% to 109.1%. | ||
| Analytical Specificity/Interference | Low cross-reactivity with common interfering substances and other infectious agents. Ideally, no equivocal or reactive results in non-reactive samples. | Out of 311 samples tested for cross-reactivity and interference, 9 samples (2.9%) that were non-reactive by another commercial assay were equivocal or reactive in the Access Toxo IgG Assay. Most categories showed 0 equivocal/reactive results. No significant effect from bilirubin, triolein, albumin, or hemoglobin. |
| Reproducibility (Total %CV) | Consistent results across different sites, calibration methods, and runs. While specific %CV thresholds are not stated as acceptance criteria, industry standards for immunoassays typically define acceptable variability. | Combined Results (Daily Calibration): Average total %CV was 12.6% (ranging from 10.3% to 20.0% across samples A001-A007). |
| Combined Results (Stored Calibration): Average total %CV was 15.3% (ranging from 13.7% to 17.3% across samples A001-A007). | ||
| Method Agreement (Predicate Comparison) | High positive and negative agreement with the predicate device (Abbott AxSYM Toxo IgG method). | Positive Agreement: Ranged from 80.0% to 99.4% across different sites and sample types. |
| Negative Agreement: Ranged from 94.7% to 100% across different sites and sample types. | ||
| CDC Toxoplasma 1998 Human Serum Panel | 100% sensitivity and specificity (as demonstrated by predicate devices or general expectations for such panels). | Exhibited 100% sensitivity and 100% specificity with the 100-member CDC Toxoplasma 1998 Human Serum Panel. |
2. Sample Size Used for the Test Set and Data Provenance:
- Analytical Specificity/Interference: 311 samples
- Reproducibility: 9 serum samples, tested over 7 days with 5 replicates per run per day, across 3 sites (total N=35 replicates per sample per site category). Total 105 replicates for combined results.
- Method Comparison (Predicate):
- Site 1: 406 samples (frozen, predominantly prenatal screening, also males/non-pregnant females). Provenance: South-central France.
- Site 2: 28 samples (fresh) and 433 samples (frozen) (prenatal screening, also males/non-pregnant females). Provenance: Northeastern United States.
- Site 3 (Manufacturer's site): 558 prenatal specimens (frozen). Provenance: North-central France.
- CDC Toxoplasma 1998 Human Serum Panel: 100-member panel. Provenance: CDC (United States).
- Data Provenance: The data used for method comparison was from various locations including south-central France, north-central France, and the northeastern United States. Sample types included prenatal screening populations, males, and non-pregnant females. The data included both prospective (fresh) and retrospective (frozen) collections.
3. Number of Experts Used to Establish the Ground Truth for the Test Set and Qualifications of Those Experts:
The document does not explicitly state the number or qualifications of experts used to establish the ground truth for the test sets.
- For the analytical studies (sensitivity, linearity, specificity, reproducibility), the "ground truth" is based on the inherent properties of the samples (e.g., known concentrations of WHO standards, defined interfering substances).
- For the method comparison studies, the "ground truth" was established by the predicate device (Abbott AxSYM Toxo IgG method). As such, no human experts were involved in establishing the ground truth for these comparison studies.
- For the CDC Toxoplasma 1998 Human Serum Panel, the panel itself is a "masked, characterized serum panel." This implies the CDC (a reputable organization) established the true positive/negative status of these samples through their own established methods, which may involve expert consensus or other reference methods, but the specifics are not detailed here.
4. Adjudication Method for the Test Set:
- None specifically described for expert adjudication. The "ground truth" for method comparison was the result from the predicate device. If there were discrepancies between the new device and the predicate, the document does not describe a process of expert adjudication to resolve these. Discrepancies are simply presented as part of the agreement tables.
5. 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:
- Not applicable. This device is an automated immunoassay for in vitro diagnostic testing, not an imaging device or a system requiring human interpretation with AI assistance. Therefore, an MRMC comparative effectiveness study involving human readers and AI assistance was not performed.
6. If a Standalone (i.e. algorithm only without human-in-the-loop performance) was done:
- Yes, this was a standalone study. The Access Toxo IgG Assay is an automated immunoassay system. All the performance data (analytical sensitivity, linearity, specificity, reproducibility, and method comparison) represents the performance of the algorithm/device alone, without human interpretation of the assay results during the testing process. Human intervention would be limited to standard laboratory procedures (sample loading, maintenance, result interpretation post-analysis).
7. The Type of Ground Truth Used:
- Predicate device results: For the method comparison studies, the results from the Abbott AxSYM Toxo IgG method served as the comparative ground truth.
- Internationally recognized standards: For dilution recovery/linearity, the Third International Standard for Anti-Toxoplasma Serum (TOXM) from WHO was used.
- Characterized serum panels: The CDC Toxoplasma 1998 Human Serum Panel, a masked and characterized panel, was used to assess sensitivity and specificity.
- Known properties of samples/substances: For analytical sensitivity, specificity, and reproducibility, the ground truth was based on the inherent characteristics of the samples (e.g., low-dose samples, samples with known interferents).
8. The Sample Size for the Training Set:
The document does not provide details on a separate "training set" as it is typically understood in machine learning. This is an immunoassay device, and its development likely involved internal optimization and validation rather than training a machine learning model on a distinct dataset. If any "training" refers to internal development and optimization, the size and nature of such internal datasets are not disclosed. The studies described are primarily for validation and verification.
9. How the Ground Truth for the Training Set Was Established:
- As noted above, the concept of a "training set" as in machine learning is not directly applicable here. The document describes validation studies rather than a training process. Therefore, how the "ground truth for the training set" was established is not provided.
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