(44 days)
The FT4 Method is used in the aca® plus immunoassay system to quantitatively measure free thyroxine (FT4) in human serum and heparinized plasma.
The FT4 assay is a one-step competitive enzyme immunoassay. Patient sample is added by the aca® plus to a reaction vessel containing chromium dioxide particles coated with monoclonal antibodies specific for FT4 and T3-alkaline phosphatase conjugate reagent. A particle/ FT4/ conjugate sandwich forms during an incubation period. The sandwich is washed to remove any unbound conjugate. The mixture is resuspended and the sandwich is transferred by the aca® plus to an FT4 test pack. The FT4 test pack is then placed into an aca® discrete clinical analyzer.
The bound alkaline phosphatase triggers an amplification cascade, resulting in the formation of a colored product. The color change measured at 510nm is directly proportional to the concentration of free thyroxine present in the patient sample.
The provided document describes a medical device, the "aca® plus Free Thyroxine (FT4) Method," and its comparison to a predicate device, the "Abbott Laboratories IMx® Free T4." However, it does not explicitly state specific acceptance criteria in terms of numerical thresholds for device performance (e.g., accuracy, sensitivity, specificity, precision targets). Instead, it relies on a "substantial equivalence" comparison to a predicate device.
Therefore, the following analysis will focus on what can be inferred from the provided text regarding performance metrics and the study conducted.
1. A table of acceptance criteria and the reported device performance
| Performance Metric | Acceptance Criteria (Implied) | Reported Device Performance (aca® plus FT4 vs. IMx® Free T4) |
|---|---|---|
| Correlation Coefficient (r) | Statistically significant correlation, indicative of good agreement with predicate device. (Specific numerical threshold not provided, but typically >0.90 is considered strong correlation for method comparison) | 0.9076 |
| Slope (m) | Close to 1 (indicating proportional agreement) | 0.94 |
| Intercept (b) | Close to 0 (indicating absence of systematic difference) | 0.16 |
Study Proving Device Meets Acceptance Criteria:
The study described is a split sample comparison between the aca® plus FT4 Method and the IMx® Free T4 assay. The performance metrics (correlation coefficient, slope, and intercept) were calculated from this comparison. The conclusion of substantial equivalence is based on these results.
2. Sample size used for the test set and the data provenance
- Sample Size for Test Set: 146 clinical patient samples.
- Data Provenance: The document does not explicitly state the country of origin. It refers to "clinical patient samples," implying they were obtained in a clinical setting. Given Dade International Inc.'s address in Newark, DE, USA, it is highly probable the data is US-based. The study design is retrospective, as it involves testing previously collected clinical patient samples with both devices.
3. Number of experts used to establish the ground truth for the test set and the qualifications of those experts
This information is not provided in the document. The "ground truth" for this study is the measurement obtained from the predicate device (IMx® Free T4 assay), not a consensus of experts or a pathology report.
4. Adjudication method for the test set
This information is not applicable/provided. The study relies on direct comparison of measurements from two automated devices, not human interpretation requiring adjudication.
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
No, a multi-reader multi-case (MRMC) comparative effectiveness study was not done. This document describes the performance of an automated in-vitro diagnostic (IVD) assay, not an AI-assisted diagnostic tool that requires human reader interpretation.
6. If a standalone (i.e. algorithm only without human-in-the-loop performance) was done
Yes, a standalone performance study was done in the sense that the aca® plus FT4 Method itself is an automated "algorithm" (a competitive enzyme immunoassay) that operates without direct human intervention in the measurement process. The study compares its results to another standalone automated device.
7. The type of ground truth used
The "ground truth" for comparison in this study is the measurements obtained from the predicate device (Abbott Laboratories IMx® Free T4). This is a common approach for demonstrating substantial equivalence for new IVD devices.
8. The sample size for the training set
This information is not provided and is likely not applicable in the context of this specific regulatory submission for a traditional immunoassay device. Immunoassays are typically developed and optimized through laboratory studies, but not "trained" with a distinct dataset in the same way machine learning algorithms are.
9. How the ground truth for the training set was established
This information is not provided and is not applicable for the reasons stated above.
§ 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.