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The Access Free T4 assay is a paramagnetic particle, chemiluminescent immunoassay for the quantitative determination of free thyroxine levels in human serum and plasma (heparin) for the diagnosis and treatment of thyroid diseases using the Access Immunoassay Systems.

Assay type: two-step, competitive

The Access Free T4 assay is a two-step enzyme immunoassay. The Access Free T4 assay consists of the reagent pack and calibrators. Other items needed to run the assay include substrate and wash buffer. The Access Free T4 reagent pack, Access Free T4 calibrators, along with Wash Buffer II are designed for use with the Access Immunoassay Systems in a clinical laboratory setting.

The Access Free T4 contains the following components:

• R1a: Dynabeads paramagnetic particles coated with streptavidin and mouse monoclonal anti-Thyroxine (T4) coupled to biotin; preservative
• R1b: TRIS buffered saline with protein (avian), surfactant, preservative
• R1c: TRIS buffered saline with protein (avian), surfactant, preservative.
• R1d: Triiodothyronine-alkaline phosphatase (bovine) conjugate in a TRIS buffer with protein (avian), surfactant, preservative.
• R1e: TRIS buffer with protein (avian and murine), surfactant, preservative

The provided 510(k) summary describes the Access Free T4 assay, a paramagnetic particle, chemiluminescent immunoassay for the quantitative determination of free thyroxine levels in human serum and plasma for the diagnosis and treatment of thyroid diseases.

Here's an analysis of the acceptance criteria and the study that proves the device meets them:

1. Table of Acceptance Criteria and Reported Device Performance

The document outlines acceptance criteria and performance for several studies.

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

• Method Comparison: 163 serum samples.
• Imprecision: For both Access 2 and Dxl 9000, "multiple samples" were tested in duplicate in 2 runs per day for a minimum of 20 days. The tables show N values per sample type ranging from 80 to 84 (representing the total number of replicates over the 20+ days for each control sample).
• Detection Capability (LoB, LoD, LoQ): "multiple reagent lots and 3 instruments over a minimum of 3 days" (LoB) and "multiple reagent lots and 3 instruments over a minimum of 5 days" (LoD, LoQ).
• Analytical Specificity: Serum samples with two concentrations of Free T4, tested in replicates of six each.
• Interference: Patient serum samples with two levels of Free T4, with 6 to 12 replicates tested for each control sample preparation.
• Sample Type Comparison: A minimum of 40 matched sets of patient samples were tested with each reagent lot. Specifically, 41 matched sets for Access 2 and 43 matched sets for Dxl 9000 were reported.

Data Provenance: The document does not explicitly state the country of origin of the data or whether it was retrospective or prospective. Given the nature of these clinical performance studies for an in vitro diagnostic device, it is typically prospective, involving controlled testing in a laboratory setting with collected human samples. The term "patient serum samples" suggests human origin.

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

This section is not applicable to this type of device (in vitro diagnostic immunoassay). The "ground truth" for an immunoassay is typically established by reference methods, consensus methods, or highly characterized samples, not by expert human readers. The predicate device itself acts as a comparative standard in the method comparison study.

4. Adjudication Method

This section is not applicable for this type of device as there is no human interpretation or decision-making process that would require adjudication.

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

This section is not applicable. This device is an automated immunoassay for quantitative determination of a specific analyte (Free T4), not an imaging or diagnostic device that relies on human reader interpretation (with or without AI assistance).

6. Standalone Performance Study

Yes, the entire set of studies described (Method Comparison, Imprecision, Detection Capability, Linearity, Analytical Specificity, Interference, Sample Type Comparison) represents the standalone performance of the modified device (Access Free T4) when compared against the predicate device or a recognized standard (e.g., CLSI guidelines). The performance metrics provided (slope, correlation, %CV, SD, LoB, LoD, LoQ, % difference) quantify the device's accuracy, precision, and analytical characteristics.

7. Type of Ground Truth Used

The ground truth used depends on the specific study:

• Method Comparison: The predicate device (Access Free T4 Assay on the Access Immunoassay Analyzer K982250) served as the comparator or "reference" for comparison.
• Imprecision: Statistical methods define precision (e.g., repeatability, within-laboratory variability). Control samples with known target values serve as the basis for evaluation.
• Detection Capability (LoB, LoD, LoQ): These limits are derived statistically from measurements of blank samples and low-concentration samples.
• Linearity: Expected proportional changes in analyte concentration across a range are compared against measured values.
• Analytical Specificity and Interference: Known concentrations of potential cross-reactants or interferents added to serum samples with known Free T4 levels are used. The "true" effect is zero interference/cross-reactivity.
• Sample Type Comparison: Matched patient samples (serum vs. plasma) are used, where the expectation is agreement between results from different sample matrices from the same individual.

8. Sample Size for the Training Set

This document only describes analytical performance studies for the modified device. There is no mention of a "training set" in the context of machine learning or AI, as this is an immunoassay device, not a software algorithm that would typically undergo a training phase.

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

This is not applicable as there is no training set for this type of device.

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The ACCESS® Free T4 Assay is a paramagnetic particle, chemiluminescent immunoassay for the quantitative determination of free thyroxine levels in human or plasma (heparin) using the ACCESS® Immunoassav System. A free thyroxine test system is a device intended to measure free (not protein bound) thyroxine (thyroid hormone) in human serum or plasma (heparin). Levels of free thyroxine in plasma are thought to reflect the amount of thyroxine hormone available to the cells and may therefore determine the clinical metabolic status of thyroxine. Measurements obtained by this device are used in the diagnosis and treatment of thyroid diseases.

The ACCESS® Free T4 reagents and the ACCESS® Immunoassay Analyzer comprise the ACCESS® Immunoassay System for the quantitative determination of free thyroxine in human serum or plasma (heparin).

The provided document describes the ACCESS® Free T4 assay, an in vitro diagnostic device, and its substantial equivalence to a predicate device for the quantitative determination of free thyroxine. Since this is an in vitro diagnostic device, the acceptance criteria and study designs are different from a typical AI/ML-based medical device that processes images or other patient data. The concepts of "human readers," "AI assistance," "ground truth," "training set," and "test set" in the context of AI/ML are not directly applicable here.

However, I can extract the closest analogous information from the document to answer your questions as best as possible, interpreting the studies described for an in vitro diagnostic device.

Here's a breakdown based on the provided information:

1. Table of Acceptance Criteria and Reported Device Performance

For in vitro diagnostics, "acceptance criteria" usually refer to established performance characteristics that demonstrate the device is fit for its intended use and comparable to existing methods. "Reported device performance" refers to the results obtained from studies evaluating these characteristics.

Note: The acceptance values for these criteria (e.g., what an acceptable r-value or %CV range is) are not explicitly stated in the provided document but are implied by the FDA's clearance based on the reported performance demonstrating substantial equivalence. The predicate device's performance would serve as an implicit benchmark for these.

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

• Test Set Sample Size: 327 samples were used for the correlation study to compare the ACCESS® Free T4 assay with the predicate device (Abbott IMx® Free T4 assay).
• Data Provenance: Not explicitly stated (e.g., country of origin). The document does not specify if the samples were retrospective or prospective, or from a specific demographic.

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

This concept is not directly applicable to an in vitro diagnostic device like the ACCESS® Free T4 assay, which measures a biochemical marker. The "ground truth" for these devices is typically established through a combination of:

• Reference methods or established predicate devices (as seen in the correlation study).
• Certified calibrators and controls with known analyte concentrations.
• The inherent biochemical process being measured.

There are no "experts" in the sense of human readers/interpreters establishing ground truth for the measurement itself.

4. Adjudication Method for the Test Set

Not applicable. This concept is relevant for studies where human interpretation is involved and discrepancies need to be resolved. For an IVD, the measurement output is quantitative.

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

No, an MRMC comparative effectiveness study was not done. These types of studies are typically performed for imaging or interpretation-based diagnostic devices where multiple human readers evaluate cases, potentially with and without AI assistance, to assess improvements in diagnostic accuracy or efficiency.

6. If a Standalone (Algorithm Only Without Human-in-the-Loop Performance) Was Done

Yes, the studies described are essentially "standalone" performance evaluations for the in vitro diagnostic device.

• Precision studies: Evaluate the inherent reproducibility of the device's measurements.
• Analytical Sensitivity: Determines the lowest quantifiable level for the device.
• Correlation study: Compares the device's quantitative outputs directly against those of a predicate device.

The ACCESS® Free T4 assay is a fully automated measurement system (immunoassay analyzer) that provides a quantitative result without direct human interpretation in the measurement process. "Human-in-the-loop" would refer to a scenario where a human modifies or interprets the device's direct output to reach a final diagnosis, which is not the primary function being evaluated here for the measurement system itself. The human-in-the-loop aspect for such devices is typically in the clinician's interpretation of the result in the context of the patient's clinical picture.

7. The Type of Ground Truth Used

For the correlation study, the "ground truth" was established by the results from the predicate device, the Abbott IMx® Free T4 assay. For precision and sensitivity, the "ground truth" relies on the known concentrations of controls and calibrators, which are themselves traceable to established reference methods or standards.

8. The Sample Size for the Training Set

The document does not explicitly mention a "training set" in the context of AI/ML development. For an in vitro diagnostic device, the development process might involve numerous samples for assay optimization, reagent formulation, and initial validation. However, this is distinct from "training data" for an AI algorithm. The 327 samples for the correlation study and the samples used for precision and sensitivity are considered "test" or "validation" samples in this context.

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

Not applicable, as there is no explicitly defined "training set" in the AI/ML sense for this in vitro diagnostic device. The "ground truth" for developing such assays involves chemical and biological analyses, calibration standards, and comparison to existing validated methods during the development and optimization phases.

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