(31 days)
The FT4 Method for the Dimension® RxL clinical chemistry system with the heterogeneous immunoassay module is used to quantitatively measure free thyroxine (FT4) in human serum and heparinized plasma.
The FT4 assay is a two-step competitive enzyme immunoassay. Sample is incubated with chromium dioxide particles, coated with monoclonal antibodies specific for FT4 to form a particle/T4 complex. Particles are separated magnetically and the supernatant removed. The particle/T4 complex is incubated with conjugate reagent to react with unoccupied binding sites on the particles. Unbound conjugate is removed by washing. The bound alkaline phosphatase triggers an amplification cascade, resulting in the formation of a colored product. The color change measured at 510nm is inversely proportional to the concentration of free thyroxine present in the patient sample.
Here's a breakdown of the acceptance criteria and study information for the Dade International Inc. FT4 Method for the Dimension® RxL Clinical Chemistry System, based on the provided text:
Acceptance Criteria and Reported Device Performance
| Acceptance Criteria | Reported Device Performance |
|---|---|
| Correlation Coefficient (r) | 0.968 |
| Slope | 0.963 |
| Intercept | 0.02 ng/dL |
Study Details
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Sample Size Used for the Test Set and Data Provenance:
- Sample Size: 156 clinical patient samples.
- Data Provenance: The document does not specify the country of origin, but refers to "clinical patient samples," implying human samples. It's a retrospective comparison, as it involved existing samples.
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Number of Experts Used to Establish the Ground Truth for the Test Set and Qualifications of Those Experts:
- This information is not provided in the given text. For an immunoassay, the "ground truth" would typically refer to the reference method result against which the new device is compared.
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Adjudication Method for the Test Set:
- This information is not applicable to this type of study which is comparing a new device to a predicate device. Adjudication methods like 2+1 or 3+1 are common in studies involving human interpretation of images or symptoms, where discrepancies need to be resolved. This study focuses on quantitative measurement agreement.
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If a Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study Was Done:
- No, an MRMC study was not done. This study is a "split sample comparison" between the new FT4 method and a predicate device (Abbott Imx® Free T4 assay). MRMC studies are typically used for diagnostic imaging or interpretation tasks where multiple human readers assess cases.
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If a Standalone (i.e., algorithm only without human-in-the-loop performance) Was Done:
- Yes, this is effectively a standalone performance study. The device itself is an automated clinical chemistry system. The comparison is between the quantitative output of the new device and the quantitative output of the predicate device, both operating as automated systems. There is no human "loop" being evaluated in this context.
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The Type of Ground Truth Used:
- The "ground truth" in this context is the results obtained from the predicate device (Abbott Imx® Free T4 assay). The study establishes equivalence to an already approved and accepted method, using its results as the comparative standard.
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Sample Size for the Training Set:
- This information is not explicitly provided. Immunoassays are typically developed and validated using a range of samples during their design phase, but the document focuses on the validation against the predicate, not the training of the assay itself.
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How the Ground Truth for the Training Set Was Established:
- As the training set size and details are not provided, how its ground truth was established is also not detailed. For an immunoassay, the "ground truth" for training would involve characterizing the assay's response to known concentrations of the analyte (FT4) and optimizing its components and procedures.
§ 862.1695 Free thyroxine test system.
(a)
Identification. A free thyroxine test system is a device intended to measure free (not protein bound) thyroxine (thyroid hormone) in serum or plasma. 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.(b)
Classification. Class II.