TSH-CTK-3 IRMA

K041014 · DiaSorin, Inc. · JLW · Jul 14, 2004 · Clinical Chemistry

Device Facts

• Record ID: K041014
• Device Name: TSH-CTK-3 IRMA
• Applicant: DiaSorin, Inc.
• Product Code: JLW · Clinical Chemistry
• Decision Date: Jul 14, 2004
• Decision: SESE
• Submission Type: Traditional
• Regulation: 21 CFR 862.1690
• Device Class: Class 2

Indications for Use

The TSH-CTK-3 is an immunoradiometric assay (IRMA) for the quantitative determination of Thyroid Stimulating Hormone(Thyrotropin) in human serum. Measurements of TSH levels are used as an aid in the diagnosis of thyroid and pituitary disorders.

Device Story

TSH-CTK-3 is an immunoradiometric assay (IRMA) for quantitative TSH measurement in human serum. Device utilizes two monoclonal antibodies: one labeled with Iodine-125 (tracer) and one immobilized on tube inner surface. During incubation, antibodies form sandwich-type complex with TSH in sample. Unbound tracer removed via wash step; radioactivity of bound fraction measured. Radioactivity is directly proportional to TSH concentration. Standard curve constructed using known TSH standards (calibrated against WHO 2nd IRP 80/558) to determine unknown sample values. Used in clinical laboratory settings by trained personnel. Results assist clinicians in diagnosing thyroid and pituitary disorders.

Clinical Evidence

Bench testing only. Performance evaluated via precision (intra-assay CV 2-10.6%, inter-assay CV 5-13%), linearity (r=0.998), and recovery (97-101%). Analytical sensitivity is 0.04 mU/L; functional sensitivity is 0.09 mU/L. Method comparison against predicate (n=95) yielded r=0.99. Interference testing performed for hemoglobin, bilirubin, cholesterol, triglycerides, and HAMA. Reference range established using 100 healthy adults (mean 1.35 mU/L, range 0.25–3.51 mU/L).

Technological Characteristics

Quantitative immunoradiometric assay (IRMA). Components: mouse monoclonal anti-TSH antibody-coated tubes, 125I-labeled mouse monoclonal anti-TSH tracer. Energy source: gamma counter for radioactivity detection. Standards: 7-level human serum-based calibrators, traceable to WHO 2nd IRP 80/558. Controls: 3-level human serum-based. Complies with NCCLS guidelines EP6-A (linearity), EP5-A (precision), and EP7-A (interference).

Indications for Use

Indicated for the quantitative determination of TSH in human serum to aid in the diagnosis of thyroid or pituitary disorders in patients. For professional use only in clinical laboratory settings.

Regulatory Classification

Identification

A thyroid stimulating hormone test system is a device intended to measure thyroid stimulating hormone, also known as thyrotrophin and thyrotrophic hormone, in serum and plasma. Measurements of thyroid stimulating hormone produced by the anterior pituitary are used in the diagnosis of thyroid or pituitary disorders.

Predicate Devices

• Ventrex hTSH 125I IRMA (k920856)

Submission Summary (Full Text)

{0}

510(k) SUBSTANTIAL EQUIVALENCE DETERMINATION
DECISION SUMMARY
DEVICE ONLY TEMPLATE

A. 510(k) Number:
k041014

B. Purpose for Submission:
Clearance of new device

C. Analyte:
Thyrotropin (TSH)

D. Type of Test:
Quantitative Immunoradiometric assay

E. Applicant:
DiaSorin, Inc.

F. Proprietary and Established Names:
TSH-CTK-3 IRMA

G. Regulatory Information:
1. Regulation section:
21 CFR § 862.1690, Thyroid stimulating hormone test system
862.1150, Calibrator
862.1660, Quality control material (assayed and unassayed)
2. Classification:
Class II
3. Product Code:
JLW, Radioimmunoassay, thyroid-stimulating hormone
JIT, Calibrator, secondary
JJX, Single (specified) analyte controls (assayed and unassayed)
4. Panel:
Clinical Chemistry (75)

H. Intended Use:
1. Intended use(s):
The DiaSorin TSH-CTK-3 IRMA is an immunoradiometric assay for the quantitative determination of thyrotropin (TSH) in human serum.

Measurements of TSH levels are used as an aid in the diagnosis of thyroid or pituitary disorders.

{1}

Page 2 of 7

2. Indication(s) for use:

See Intended Use section above

3. Special condition for use statement(s):

For professional use only in clinical laboratory settings

4. Special instrument Requirements:

General high complexity laboratory equipment, gamma counter

I. Device Description:

The TSH-CTK-3 IRMA kit consists of a radiolabeled tracer containing mouse monoclonal anti-intact TSH antibodies in buffer, tubes coated with mouse monoclonal anti-TSH- $\beta$ antibodies, wash buffer, calibrators and control materials.

J. Substantial Equivalence Information:

1. Predicate device name(s):

Ventrex hTSH $^{125}$ I IRMA

2. Predicate K number(s):

k920856

3. Comparison with predicate:

| Similarities | | |
| --- | --- | --- |
| Item | Device | Predicate |
| Intended use | For in vitro diagnostic use. For the quantitative determination of thyrotropin (TSH) in human serum. Measurements of TSH are used as an aid in the diagnosis of thyroid or pituitary disorders. | For in vitro diagnostic use. For the quantitative determination of thyrotropin (TSH) in human serum. |
| Assay type | IRMA | IRMA |
| Coated tube | Mouse monoclonal anti-hTSH antibodies | Mouse monoclonal anti-hTSH antibodies |
| Tracer | 125I labeled mouse monoclonal anti-hTSH antibodies | 125I labeled goat anti-hTSH |
| Standards | 7 levels – human serum based | 8 levels – porcine serum based |
| Differences | | |
| Item | Device | Predicate |
| Kit Controls | 3 levels – human serum based | None |

{2}

Page 3 of 7

# K. Standard/Guidance Document Referenced (if applicable):

NCCLS Guideline EP6-A – Evaluation of the Linearity of Quantitative Analytical Methods

NCCLS Guideline EP5-A – Evaluation of Precision Performance of Clinical Chemistry Devices

NCCLS Guideline EP7-A – Interference Testing in Clinical Chemistry

# L. Test Principle:

Sample and tracer antibody solution are added to the antibody coated tubes. TSH in the sample reacts with both the antibody on the tube and the radiolabeled tracer antibody to form a sandwich complex on the inner surface of the tube. Wash steps remove excess material and radioactivity in the tube is measured in a gamma counter. The amount of radioactivity in the tube is proportional to the amount of TSH in the sample. The concentration is extrapolated from a standard curve generated from the kit calibrators and verified by the kit controls.

# M. Performance Characteristics (if/when applicable):

1. Analytical performance:

a. Precision/Reproducibility:

Four serum pools were assayed in duplicate twice a day for 20 days (total n = 80 replicates). Multiple technicians and multiple kit lots were used in the analysis. In addition, 2 serum pools with TSH values below 0.6 mU/L were assayed in quadruplicate once per day for five days. Results for intra- and Inter-assay precision are summarized below (units = mU/L).

| Pool | Mean | Intra-Assay | | Inter-Assay | |
| --- | --- | --- | --- | --- | --- |
| | | SD | % CV | SD | % CV |
| 1 | 0.136 | 0.014 | 10.6 | 0.018 | 13 |
| 2 | 0.187 | 0.008 | 4.6 | 0.024 | 13 |
| A | 0.6 | 0.04 | 6 | 0.1 | 12 |
| B | 1.6 | 0.1 | 5 | 0.1 | 7 |
| C | 16.8 | 0.3 | 2 | 0.8 | 5 |
| D | 40.8 | 0.8 | 2 | 2 | 5 |

b. Linearity/assay reportable range:

The reportable range of this assay is determined by the range of the calibrators determining the standard curve and the functional sensitivity of the assay. This device contains calibrators from 0.02 to 80 mU/L TSH. The useable range is 0.09 to 80 mU/L.

Eight serum pools spanning the reportable range were tested in quadruplicate. Results are summarized below (units = mU/L).

{3}

| Sample | Expected Value | Mean Observed Value |
| --- | --- | --- |
| 1 | 0.125 | 0.09 |
| 2 | 10.11 | 8.87 |
| 3 | 20.1 | 19.3 |
| 4 | 30.09 | 29.14 |
| 5 | 40.08 | 39.62 |
| 6 | 50.06 | 47.9 |
| 7 | 60.05 | 56.3 |
| 8 | 70.04 | 63.85 |

Observed $= 0.93(\text{Expected}) + 0.52$ ; $\mathbf{r} = 0.998$

Seven samples were diluted with zero standard to span the reportable range and were tested in duplicate. Results are summarized below (units = mU/L).

Observed $= 1.02(\text{Expected}) + 0.19$ ; $\mathbf{r} = 0.999$

Recovery was evaluated by the addition of known amounts of TSH to 11 serum samples. Percent recoveries ranged from $97 - 101\%$ of expected..

# c. Traceability (controls, calibrators, or method):

The kit contains a 7 point calibrator set to be run in duplicate with every assay. A standard curve generated from the results provides the basis for extrapolation of sample TSH concentration. The calibrators are made by adding human TSH gravimetrically to human serum matrix that has been previously stripped of endogenous TSH. The calibrators are traceable to a Master calibration curve that is standardized to the WHO $2^{\text{nd}}$ IRP 80/558. The targeted TSH values for the 7 calibrators are 0.02, 0.16, 0.31, 1.25, 5.0, 20, and $80 \mathrm{mU} / \mathrm{L}$ TSH. Actual concentrations are provided with each kit.

The kit contains 3 levels of controls which are prepared gravimetrically by the addition of human TSH into a human serum based matrix that has been previously stripped of endogenous TSH. The controls are validated against 3 lots of calibrators and the actual values are provided with each kit.

# d. Detection limit:

Functional sensitivity was determined by measuring 14 samples assayed in quadruplicate once a day for 5 days. The concentration at which assay imprecision was calculated to be $20\%$ CV (by interpolation) is $0.09 \, \mathrm{mU/L}$ .

The analytical sensitivity, defined as the lowest concentration of TSH that can be distinguished from the zero standard by 2 standard deviations, was assessed by measuring 40 replicates of the zero standard. A corresponding standard curve was generated using the mean of the 40 measurements as the zero standard, and the concentration at 2 SD above the zero was determined to be $0.04\mathrm{mU / L}$ .

{4}

The potential for a high dose hook effect was evaluated for this assay by serially diluting a stock solution containing $200,000\mathrm{mU / L}$ TSH with zero calibrator down to $0.4\mathrm{mU / L}$ . Effects were observed above the range of the highest calibrator. The package insert will reflect the data (summarized below) and state that results above the highest calibrator should be reported as “> highest calibrator” or may need to be diluted further until a result is achieved in the range of the assay. (units = mU/L)

| Expected | Observed |
| --- | --- |
| 200000 | 0.72 |
| 100000 | 2.2 |
| 50000 | 2.91 |
| 25000 | 6.18 |
| 12500 | 12.7 |
| 6250 | 42.6 |
| 3125 | 125 |
| 1563 | 149 |
| 781 | 149 |
| 391 | 146 |
| 195 | 119 |
| 98 | 8.4 |
| 49 | 40 |
| 24 | 18.9 |
| 12 | 8.9 |
| 6 | 4.33 |
| 3 | 2.16 |
| 1.5 | 1.14 |
| 0.8 | 0.57 |
| 0.4 | 0.26 |

# e. Analytical specificity:

To test the crossreactivity of this device to similar endogenous analytes, serum samples were spiked with the analyte and compared to a non-spiked base pool. No analytes tested significantly cross-reacted in this analysis. Results are summarized below:

| Analyte | Concentration of Spiked Analyte | % Cross Reactivity |
| --- | --- | --- |
| FSH | 1400 mIU/mL | 0.0001 |
| LH | 5500 mIU/mL | 0.00003 |
| hCG | 71210 mIU/mL | 0.000001 |

Three levels of control serum were tested in the presence of increasing levels of hemoglobin, bilirubin, cholesterol, or triglycerides to determine any interferences. No

{5}

Page 6 of 7

interference was seen up to 500 mg/dL hemoglobin and up to 1000 mg/dL cholesterol. Bilirubin interferes with the assay results at and above 30 mg/dL. Triglycerides interfere with the assay results at and above 330 mg/dL.

The effect of Human Anti-Mouse Antibodies (HAMA) was evaluated. Eleven HAMA samples were tested neat and spiked with a TSH pool. Percent Recovery was then evaluated. No interference was observed in the presence of HAMA antibodies. However, the sponsor has included a cautionary statement in their labeling stating that HAMA samples may cause falsely low or elevated results.

f. Assay cut-off:
Not Applicable

2. Comparison studies:
a. Method comparison with predicate device:

Serum samples (n = 95 samples, including 39 purchased samples and 25 samples spiked to achieve samples with high TSH values) were tested in duplicate using the device and the predicate and compared. The results are summarized as follows:

Device = 1.08(Predicate) + 0.22; r = 0.99

b. Matrix comparison:

Serum samples from 46 apparently healthy donors were aliquoted and matched samples were stored at 4°C or -20°C, respectively. The samples were then tested and compared to establish whether frozen samples were equivalent to fresh samples in this assay. No significant differences were observed between the two sets of matched samples.

3. Clinical studies:
a. Clinical sensitivity:
Not applicable
b. Clinical specificity:
Not applicable
c. Other clinical supportive data (when a and b are not applicable):
Not applicable

4. Clinical cut-off:
Not applicable

5. Expected values/Reference range:

Serum samples from 100 apparently healthy adults were assayed with the device. Donors had no known thyroid illness nor were they taking medications known to affect thyroid function. Results of the reference range study for this device in serum are summarized below.

Number of Subjects 100
Mean 1.35 mU/L

{6}

Page 7 of 7

Median 1.13 mU/L
1 SD 0.85
Range 0.25 – 3.51 mU/L

N. Conclusion:
The submitted information in this premarket notification is complete and supports a substantial equivalence decision.