(40 days)
For the assessment of unsaturated thyroid binding proteins in serum or plasma using the Chiron Diagnostics ACS:180® Automated Chemiluminescence Systems.
The thyroid hormones triiodothyronine (T3) and thyroxine (T4) are bound primarily to thyroxine-binding globulin (TBG) and to a lesser extent thyroxine-binding prealbumin (TBPA) and albumin. The ACS:180 T Uptake assay measures the number of unoccupied binding sites on these proteins and is an indirect indicator of thyroid status.
T Uptake (TU) and total T4 are used to estimate the amount of circulating free T4. The estimate, or the Free Thyroxine Index (FTI), is a normalized measurement that remains relatively constant in healthy individuals and compensates for abnormal levels of binding proteins, which can occur in many different physical conditions.
Drugs or physical conditions that alter the patient's TBG levels or drugs that compete with endogenous T4 and T3 for protein-binding sites alter T Uptake results.
When serum contains high levels of T3 or T4, as in hyperthyroidism, fewer unoccupied binding sites are available. Conversely, in hypothyroidism, more binding sites are available.
The Chiron Diagnostics ACS:180 TUp assay is a double antibody competitive immunoassay using, chemiluminescent technology. The sample is incubated with Lite Reagent, which is composed of acridinium ester-labeled T3-BGG (bovine gamma globulin) and unlabeled T3. The unlabeled T3 in the Lite Reagent fills available thyroid-binding sites in the sample. The acridinium ester-labeled T3-BGG does not bind to the binding proteins in the sample.
The acridinium ester-labeled T3-BGG and unlabeled T3 compete for monoclonal mouse anti-T3 antibody in the Solid Phase. The monoclonal mouse anti-T3 antibody is bound to goat anti-mouse antibody, which is covalently coupled to paramagnetic particles in the Solid Phase. A greater amount of unlabeled T3 binding to the binding proteins in the sample results in more T3-BGG-acridinium ester binding to the monoclonal antibody, an indication of a higher amount of unsaturated binding proteins.
This document describes a medical device called the "Chiron Diagnostics ACS:180 TUp," a thyroid hormone uptake test system.
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Acceptance Criteria and Device Performance
The document does not explicitly define "acceptance criteria" for the device's performance in terms of accuracy or precision against a specific threshold. Instead, it presents performance characteristics such as:
- Reference Range: Established for euthyroid individuals.
- Specificity: Cross-reactivity with various compounds.
- Method Comparison: Correlation with an alternate chemiluminescent method.
- Precision: Within-laboratory precision (Total CV).
Given the absence of explicit acceptance criteria, the "Reported Device Performance" below summarizes the results provided for each characteristic.
Table of Acceptance Criteria and Reported Device Performance
| Characteristic | Acceptance Criteria (Implicit/Explicit) | Reported Device Performance |
|---|---|---|
| Expected Results | Implied: To establish a reference range for euthyroid samples for TU Ratio, % TU, and FTI based on a 95% confidence interval. (No specific numerical target given for the range itself). | Euthyroid Reference Range (95% CI): |
- TU Ratio: 0.75 – 1.23
- % TU: 22.5 – 37.0
- FTI: 1.4 – 3.1 |
| Specificity | Implied: Demonstrate low cross-reactivity with structurally similar compounds and non-target analytes. | Cross-reactivity: - L-thyroxine: 0.95 or similar) with an established reference/predicate method. | Correlation with alternate chemiluminescent method:
- T Uptake Ratio: r = 0.95
- FTI: r = 0.97 (Equation: ACS:180 TUp FTI = 1.07 * (alternate method) + 0.04) |
| Precision (Total % CV) | Implied: Demonstrate acceptable within-laboratory precision for different sample concentrations. (No specific numerical target given for %CV, but typically
§ 862.1715 Triiodothyronine uptake test system.
(a)
Identification. A triiodothyronine uptake test system is a device intended to measure the total amount of binding sites available for binding thyroid hormone on the thyroxine-binding proteins, thyroid-binding globulin, thyroxine-binding prealbumin, and albumin of serum and plasma. The device provides an indirect measurement of thyrkoxine levels in serum and plasma. Measurements of triiodothyronine uptake are used in the diagnosis and treatment of thyroid disorders.(b)
Classification. Class II. The device is exempt from the premarket notification procedures in subpart E of part 807 of this chapter subject to the limitations in § 862.9.