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The Access Thyroglobulin Antibody II assay is a paramagnetic particle, chemiluminescent immunoassay for the quantitative determination of thyroglobulin antibody levels in human serum and plasma using the Access Immunoassay Systems. The measurement of thyroid autoantibodies may aid in the diagnosis of Hashimoto's disease, nontoxic goter, and Graves' disease.

The Access Thyroqlobulin Antibody II assay is a paramagnetic particle, chemiluminescent immunoassay for the quantitative determination of thyroglobulin antibody levels in human serum and plasma using the Access Immunoassay Systems. The measurement of thyroid autoantibodies may aid in the diagnosis of Hashimoto's disease, nontoxic goiter, and Graves' disease.

The Access Thyroglobulin Antibody II assay consists of the reagent pack and calibrators. Other items needed to run the assay include substrate and wash buffers. The assay is run on Access 2 Immunoassay Analyzers.

The device modifications described in this submission impact the Access Thyroqlobulin Antibody II reagent pack only; they do not impact or change the other components that are used with this reagent pack. The modification does not affect the intended use or indications of the device or alter the fundamental scientific technology of the device.

A description of the reagent pack is provided below.

Here's an analysis of the provided text, outlining the acceptance criteria and study details for the "Access Thyroglobulin Antibody II" device:

Device: Access Thyroglobulin Antibody II

The study in the document focuses on the modified Access Thyroglobulin Antibody II assay and compares it to the previously cleared predicate device (Access Thyroglobulin Antibody II Assay, FDA 510(k) Number K112933). The goal is to demonstrate substantial equivalence of the modified device.

1. Table of Acceptance Criteria and Reported Device Performance

The document does not explicitly present acceptance criteria in a dedicated table format. Instead, it describes performance characteristics and the results obtained. I've reconstructed a table based on the implicit criteria derived from the reported performance, especially where a target value or range is given (e.g., for imprecision, biases, or correlation).

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

• Method Comparison: n = 123 samples. Data provenance not specified (country of origin, retrospective/prospective).
• Imprecision: Not specified, but involved reagent lots and instrument details suggest laboratory testing.
• Reproducibility: Not specified, but involved reagent lots and instrument details suggest laboratory testing.
• High-dose Hook Effect: Not specified how many samples were tested, but concentrations up to 50,000 IU/mL were used.
• Linearity: Not specified how many samples were tested, but both serum and plasma samples were used.
• Sensitivity (LoB, LoD, LoQ): Not specified how many samples were used, but involved 2 reagent lots and 2 instruments over a minimum of 3 days (LoB) or 5 days (LoD, LoQ).
• Analytical Specificity:
  • Cross-reactive disease states: "Samples with potential cross-reactive disease states were tested." Number of samples not specified.
  • Potential interferents: "Patient serum samples containing two levels of thyroglobulin antibody at clinically relevant concentrations of approximately 4 IU/mL and 100 IU/mL." Number of samples not specified, but specific interferents (like biotin at 3510 ng/mL) were tested.
• Matrix Comparison: Fifty (50) matched sets of serum, lithium heparin plasma, and EDTA plasma samples.

Data Provenance: The document does not specify the country of origin for any of the samples used in these studies, nor does it explicitly state if the studies were retrospective or prospective, though "patient samples" implies retrospective collection or prospective enrollment for the study.

3. Number of Experts Used to Establish Ground Truth and Qualifications

This device is an in vitro diagnostic (IVD) immunoassay, not an imaging device typically requiring expert interpretation for ground truth. Therefore, the concept of "experts" establishing ground truth in the traditional sense of clinical diagnosis (e.g., radiologists, pathologists) does not directly apply here.

For IVDs, "ground truth" is typically established by:

• Reference methods/devices.
• Certified reference materials.
• Pathology or histopathology (for certain tests).
• Clinical outcomes/diagnosis (for certain tests).
• Known concentrations in spiked samples or characterized panels.

In this document:

• The "Method Comparison" used a "commercially available immunoassay" as a comparator, which serves as a de facto reference for comparison.
• Analytical specificity testing used "potential cross-reactive disease states" and "potential interferents" for which the expected results (presence/absence of Thyroglobulin Antibody, or known interference levels) would be pre-established or determined by a reference method.
• Sensitivity studies (LoB, LoD, LoQ) involve statistical calculations based on repeated measurements of samples with very low or zero analyte concentrations, not expert consensus.
• Concentration ranges for linearity were established using characterized samples.

Therefore, no information on human experts establishing ground truth is provided, as it's not relevant for this type of device validation.

4. Adjudication Method for the Test Set

Adjudication methods (like 2+1, 3+1) are typically used for studies where multiple human readers interpret medical images or complex data, and their interpretations need to be reconciled to establish a ground truth.

Since this is an in vitro diagnostic device measuring an analyte concentration, and the gold standard for comparison typically involves laboratory methods or reference materials, an adjudication method for a test set is not applicable or described in this document. The "ground truth" for the various performance characteristics is established by analytical methods and comparisons to reference standards or predicate devices.

5. Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study

No, a multi-reader multi-case (MRMC) comparative effectiveness study was not performed. This type of study is relevant for medical imaging devices where the performance of human readers, with and without AI assistance, is evaluated using a set of cases. This document describes an in vitro diagnostic device, an immunoassay, which does not involve human interpretation of images or complex data in a way that MRMC studies would be applicable.

6. Standalone (Algorithm Only Without Human-in-the-Loop Performance) Study

Yes, the studies described are all standalone performance evaluations of the Access Thyroglobulin Antibody II assay. This means the studies assess the device's ability to measure thyroglobulin antibody levels independent of human intervention in the interpretation of the result in the context of the device's analytical performance. The Access Immunoassay Systems are automated, and the assay's performance metrics (imprecision, linearity, sensitivity, specificity, etc.) are solely based on the analytical capabilities of the device itself.

7. The Type of Ground Truth Used

The type of "ground truth" used varies depending on the specific study:

• Method Comparison: A "commercially available immunoassay" served as the comparative standard. The results from this predicate/reference immunoassay formed the basis for comparing the new device's measurements.
• Imprecision & Reproducibility: Ground truth is implicit in the known characteristics of the control materials or spiked samples used, and the statistical variability observed from repeated measurements defines the performance.
• High-dose Hook Effect & Linearity: Ground truth is established by using samples with known or precisely characterized concentrations, often prepared by dilution or spiking.
• Sensitivity (LoB, LoD, LoQ): Statistical models are used based on repeated measurements of blank samples and samples with very low (but known) analyte concentrations.
• Analytical Specificity:
  • Cross-reactive disease states: Likely involved samples from patients with these conditions, where the presence/absence of TgAb would have been characterized by a reference method or clinical diagnosis. The "ground truth" then is the expected TgAb status based on the sample's origin.
  • Potential interferents: Involved adding known concentrations of interfering substances to samples with known TgAb concentrations. The "ground truth" is the expected TgAb concentration without interference.
• Matrix Comparison: Used matched samples from different matrices (serum, plasma), where the inherent TgAb concentration within a given patient sample is the ground truth against which each matrix measurement is compared.

In summary, the ground truth for this IVD device is primarily established through comparisons to established reference methods/predicate devices, known concentrations in characterized samples (spiked or diluted), and statistical analysis of performance with control materials.

8. The Sample Size for the Training Set

The document describes studies for validation of a modified device, demonstrating substantial equivalence to a predicate. It does not mention a "training set" in the context of developing an algorithm or AI model. This is an immunoassay, not a machine learning model that typically requires a large training dataset. The studies focus on analytical performance rather than diagnostic accuracy determined by a machine learning pipeline.

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

As noted above, there is no mention of a "training set" or "ground truth" established for training in this document, as the device is an immunoassay not based on a trainable algorithm.

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