ELECSYS T4 ASSAY

K961490 · Boehringer Mannheim Corp. · CDX · Jun 13, 1996 · Clinical Chemistry

Device Facts

• Record ID: K961490
• Device Name: ELECSYS T4 ASSAY
• Applicant: Boehringer Mannheim Corp.
• Product Code: CDX · Clinical Chemistry
• Decision Date: Jun 13, 1996
• Decision: SESE
• Submission Type: Traditional
• Regulation: 21 CFR 862.1700
• Device Class: Class 2

Intended Use

Immunoassay for the in vitro quantitative determination of total thyroxine in human serum and plasma.

Device Story

Elecsys® T4 Assay is an in vitro diagnostic immunoassay for total thyroxine (T4) quantification in human serum and plasma. The device utilizes a competitive electrochemiluminescence (ECL) principle. Input: 15 μL patient sample. Process: Sample incubated with ruthenium-labeled anti-T4 antibody; biotinylated T4 and streptavidin-coated microparticles added to bind remaining antibody sites; complex captured magnetically on electrode surface; voltage applied to induce chemiluminescent emission. Output: Light intensity measured by photomultiplier, converted to concentration via instrument-specific calibration curve and master curve from reagent bar code. Used in clinical laboratory settings on the Elecsys® 2010 instrument. Results assist healthcare providers in assessing thyroid function. Benefits include automated, standardized T4 measurement with improved sensitivity compared to traditional ELISA methods.

Clinical Evidence

Bench testing only. Performance evaluated via precision (within-run and total %CV), lower detection limit (0.23 μg/dL), linearity (0.23–24.86 μg/dL), and interference studies (bilirubin, hemoglobin, lipemia, biotin). Method comparison against Enzymun-Test® T4 (N=196) yielded a correlation coefficient (r) of 0.947. Specificity assessed via cross-reactivity testing with T3 and tyrosine derivatives.

Technological Characteristics

Electrochemiluminescence immunoassay; utilizes ruthenium complex label and streptavidin-coated microparticles. Requires Elecsys® 2010 instrument. Calibration via 2-point method and reagent bar code master curve. Assay duration: 18 minutes at 37°C. Detection via photomultiplier.

Indications for Use

Indicated for the in vitro quantitative determination of total thyroxine (T4) in human serum and plasma for clinical diagnostic purposes.

Regulatory Classification

Identification

A total thyroxine test system is a device intended to measure total (free and protein bound) thyroxine (thyroid hormone) in serum and plasma. Measurements obtained by this device are used in the diagnosis and treatment of thyroid diseases.

Special Controls

*Classification.* Class II (special controls). 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.

Predicate Devices

• Enzymun T4 Assay (K901346)

Submission Summary (Full Text)

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K961490

JUN 13 1996

Diagnostics

# 510(k) Summary

## Introduction

According to the requirements of 21 CFR 807.92, the following information provides sufficient detail to understand the basis for a determination of substantial equivalence.

## 1. Submitter name, address, contact

Boehringer Mannheim Corporation
2400 Bisso Lane
P.O. Box 4117
Concord, CA 94524-4117
(510) 674 - 0690, extension 8415

Contact Person: Mary Koning

Date Prepared: April 9, 1996

## 2. Device name

Proprietary name: Elecsys® T4 Assay

Common name: Electrochemiluminescence assay for the determination of total thyroxine (T4).

Classification name: Radioimmunoassay, Total Thyroxine

## 3. Predicate device

We claim substantial equivalence to the Enzymun T4 Assay (K901346).

## 4. Device Description

The Elecsys® test principle is based on competition principle. Total duration of assay: 18 minutes (37° C).

- 1st incubation (9 minutes): Sample (15 μL) and a specific anti-T4 antibody labeled with a ruthenium complex (75 μL).
- 2nd incubation (9 minutes): After addition of biotinylated T4 (75 μL) and streptavidin-coated microparticles (35 μL), the still-free binding sites of the labeled antibody become occupied, with formation of an antibody-hapten complex. The entire complex is bound to the solid phase via interaction of biotin and streptavidin.

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Diagnostics

# 510(k) Summary, Continued

## 4. Device Description

- The reaction mixture is aspirated into the measuring cell where the microparticles are magnetically captured onto the surface of the electrode. Unbound substances are then removed with ProCell. Application of a voltage to the electrode then induces chemiluminescent emission which is measured by a photomultiplier (0.4 second read frame).
- Results are determined via a calibration curve which is instrument-specifically generated by 2-point calibration and a master curve provided via the reagent bar code.

## 5. Intended use

Immunoassay for the in vitro quantitative determination of total thyroxine in human serum and plasma.

## 6. Comparison to predicate device

The Boehringer Mannheim Elecsys® T4 Assay is substantially equivalent to other products in commercial distribution intended for similar use. Most notably it is substantially equivalent to the currently marketed Enzymun T4 Assay (K901346).

The following table compares the Elecsys® T4 Assay with the predicate device, Enzymun T4 Assay. Specific data on the performance of the test have been incorporated into the draft labeling in attachment 5. Labeling for the predicate device is provided in attachment 6.

## Similarities:

- Intended Use: Immunoassay for the in vitro quantitative determination of total thyroxine
- Sample type: Serum and plasma
- Antibody: Polyclonal Sheep anti-T4 antibodies
- Solid phase binding principle: Streptavidin/Biotin
- Assay standardization: GC/MS Gas Chromatography/Mass Spectrometry

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Diagnostics

# 510(k) Summary, Continued

## 6. Comparison to predicate device cont.

### Differences:

| Feature | Elecsys® T4 | Enzymun T4 |
| --- | --- | --- |
| Reaction test principle | Electrochemiluminescence | ELISA/1-step sandwich assay using streptavidin technology |
| Instrument required | Elecsys® 2010 | ES 300 |
| Calibration Stability | A calibration is recommended every 7 days if kit is not consumed; 4 weeks with same reagent lot if reagent is consumed within 7 days. | A calibration is required every run |

### Performance Characteristics:

| Feature | Elecsys® T4 | | | Enzymun T4 | | |
| --- | --- | --- | --- | --- | --- | --- |
| Precision | Modified NCCLS (nmol/L): | | | Modified NCCLS (μg/dL): | | |
| Level | Sample | Control 1 | Control 2 | Low | Mid | High |
| N | 60 | 60 | 60 | 120 | 120 | 118 |
| Within-Run | 33.39 | 113.10 | 180.55 | 4.55 | 6.79 | 15.49 |
| %CV | 4.7 | 2.3 | 2.0 | 2.3 | 2.4 | 2.0 |
| Total | 33.39 | 113.10 | 180.55 | 4.55 | 6.79 | 15.49 |
| %CV | 6.9 | 3.3 | 2.7 | 3.1 | 2.9 | 2.5 |
| | Modified NCCLS (μg/dL): | | | | | |
| | Sample | Control 1 | Control 2 | | | |
| N | 60 | 60 | 60 | | | |
| Within-Run | 2.60 | 8.82 | 14.08 | | | |
| %CV | 4.7 | 2.3 | 2.0 | | | |
| Total | 2.60 | 8.82 | 14.08 | | | |
| %CV | 6.9 | 3.3 | 2.7 | | | |

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Diagnostics

# 510(k) Summary, Continued

## 6. Comparison to predicate device, (cont.)

### Performance Characteristics:

| Feature | Elecsys® T4 | Enzymun T4 |
| --- | --- | --- |
| Lower Detection Limit | 0.23 μg/dL (3 nmol/L) | 0.6 μg/dL (7.7 nmol/L) |
| Linearity | 0.23 - 24.86 μg/dL (3.0 - 320 nmol/L) (with a deviation from a linear line of ±10%) | 0.6 - 25.0 μg/dL (with a deviation from a linear line of ±10%) |
| Method Comparison | Vs Enzymun-Test® T4
Least Squares
y = 1.02x + 0.85
r = 0.947
SEE = 5.39
N = 196

Passing/Bablok
y = 0.93x + 4.55
r = 0.947
SEE = 5.39
N = 196 | Vs Enzymun-Test® T4
Least Squares
y = 0.90x - 0.45
r = 0.996
SEE = 0.648
N = 78 |

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Diagnostics

# 510(k) Summary, Continued

## 6. Comparison to predicate device, (cont.)

Performance Characteristics:

| Feature | Elecsys® T4 | Enzymun T4 |
| --- | --- | --- |
| Interfering substances | No interference at: | No interference at: |
| Bilirubin | 25 mg/dL | 64.5 mg/dL |
| Hemoglobin | 1 g/dL | 1 g/dL |
| Lipemia | 1500 mg/dL | 1250 mg/dL |
| Biotin | 30 ng/mL | 200 ng/mL |
| Specificity | % Cross-reactivity | % Cross-reactivity |
| L-T4 | 100 | 100 |
| D-T4 | 100 | 100 |
| L-T3 | 1.53 | 3.5 |
| D-T3 | 1.38 | 2.9 |
| 3-iodo-L-tyrosine | 0.002 | <0.1 |
| 3,5-diiodo-L-tyrosine | 0.01 | <0.1 |
| tetraiodo-thyroacetic acid | 38.5 | 20 |

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