ABBOTT PHENOBARBITAL ASSAY

K123271 · Microgenics Corp. · DLZ · Apr 26, 2013 · Clinical Toxicology

Device Facts

• Record ID: K123271
• Device Name: ABBOTT PHENOBARBITAL ASSAY
• Applicant: Microgenics Corp.
• Product Code: DLZ · Clinical Toxicology
• Decision Date: Apr 26, 2013
• Decision: SESE
• Submission Type: Traditional
• Regulation: 21 CFR 862.3660
• Device Class: Class 2

Indications for Use

The Abbott Phenobarbital assay is for in vitro diagnostic use for the quantitative measurement of phenobarbital in human serum or plasma on the ARCHITECT cSystems. The measurements obtained are used in the diagnosis and treatment of phenobarbital overdose and in monitoring levels of phenobarbital to help ensure appropriate therapy.

Device Story

The Abbott Phenobarbital Assay is a quantitative, in vitro diagnostic immunoassay for use on the ARCHITECT c8000 clinical chemistry analyzer. It utilizes a particle-enhanced turbidimetric inhibition immunoassay (PETINIA) principle. The assay involves competition between phenobarbital in the patient sample and phenobarbital coated onto microparticles for binding sites on a mouse anti-phenobarbital antibody reagent. In the absence of the drug, the microparticles agglutinate; the presence of phenobarbital in the sample inhibits this agglutination. The analyzer measures the rate of absorbance change photometrically, which is inversely proportional to the phenobarbital concentration. The device is intended for use in clinical laboratory settings by trained personnel. Results are provided to clinicians to assess therapeutic levels or identify overdose, aiding in clinical decision-making regarding patient medication management.

Clinical Evidence

Bench testing only. Precision studies (inter-assay) performed on the ARCHITECT c8000 analyzer using serum-based controls and spiked patient samples showed total CVs ranging from 1.2% to 6.7%. Linearity was confirmed across the 2.0–80.0 μg/mL range (R²=0.998). Method comparison against the predicate (N=118) yielded a slope of 1.003 and R=0.9949. Analytical specificity and interference studies confirmed no significant cross-reactivity or interference from common compounds or endogenous substances.

Technological Characteristics

PETINIA (particle-enhanced turbidimetric inhibition immunoassay). Reagents: liquid, ready-to-use antibody reagent and phenobarbital-coated microparticle reagent. Analyzed on ARCHITECT c8000 clinical chemistry analyzer. Standards: CLSI EP5-A2 (precision), CLSI EP17-A2 (LoD/LoQ). Storage: 2-8°C. Quantitative measurement via photometric rate of absorbance change.

Indications for Use

Indicated for the quantitative measurement of phenobarbital in human serum or plasma to assist in the diagnosis and treatment of phenobarbital overdose and therapeutic drug monitoring.

Regulatory Classification

Identification

A phenobarbitol test system is a device intended to measure phenobarbital, an antiepileptic and sedative-hypnotic drug, in human specimens. Measurements obtained by this device are used in the diagnosis and treatment of phenobarbital use or overdose and in monitoring levels of phenobarbital to ensure appropriate therapy.

Predicate Devices

• Abbott Aeroset® Phenobarbital Assay (k993031)

Submission Summary (Full Text)

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

A. 510(k) Number:
k123271

B. Purpose for Submission:
New Device

C. Measurand:
Phenobarbital

D. Type of Test:
Quantitative immunoassay

E. Applicant:
Microgenics Corporation

F. Proprietary and Established Names:
Abbott Phenobarbital Assay

G. Regulatory Information:
1. Regulation section:
21 CFR 862.3660, Phenobarbital Test System
2. Classification:
Class II
3. Product code:
DLZ, Enzyme immunoassay, phenobarbital
4. Panel:
Toxicology (91)

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H. Intended Use:

1. Intended use(s):

See indication(s) for use below.

2. Indication(s) for use:

The Abbott Phenobarbital Assay is for in vitro diagnostic use for the quantitative measurement of phenobarbital in human serum or plasma on the ARCHITECT cSystems. The measurements obtained are used in the diagnosis and treatment of phenobarbital overdose and in monitoring levels of phenobarbital to help ensure appropriate therapy.

3. Special conditions for use statement(s):

For prescription use only

4. Special instrument requirements:

For use on the ARCHITECT c8000 clinical chemistry analyzer

I. Device Description:

The Phenobarbital Assay kit is supplied ready-to-use in liquid form, for storage at 2 to 8°C. Each Phenobarbital Assay kit is packaged in a rectangular cardboard box divided into three sections. One section will contain three bottles of Antibody Reagent (R1), one section will contain three bottles of Microparticle Reagent (R2), and the last section will contain the package insert. Each kit is sufficient for 300 tests.

J. Substantial Equivalence Information:

1. Predicate device name(s):

Abbott Aeroset® Phenobarbital Assay

2. Predicate 510(k) number(s):

k993031

3. Comparison with predicate:

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| Similarities | | |
| --- | --- | --- |
| Comparison | Device | Predicate |
| Proprietary name | Abbott Phenobarbital Assay | Abbott Aeroset® Phenobarbital Assay (k993031) |
| Intended Use | The Abbott Phenobarbital assay is for in vitro diagnostic use for the quantitative measurement of phenobarbital in human serum or plasma on the ARCHITECT cSystems. The measurements obtained are used in the diagnosis and treatment of phenobarbital overdose and in monitoring levels of phenobarbital to help ensure appropriate therapy. | Same |
| Sample Matrix | Human Serum or Human Plasma | Same |
| Storage | 2-8°C | Same |
| Calibrator | Liquid Ready-to-Use, six levels (0.0, 5.0, 10.0, 20.0, 40.0, and 80.0 μg/mL) | Same |
| Differences | | |
| --- | --- | --- |
| Comparison | Device | Predicate |
| Reagents | Liquid Ready-to-Use (Antibody reagent and Phenobarbital-coated microparticle reagent) | Liquid Ready-to-Use (Antibody reagent and Phenobarbital-labeled enzyme reagent) |
| Assay Range | 2.0 to 80.0 μg/mL | 0.5 to 80.0 μg/mL |

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

CLSI EP5-A2: Evaluation of Precision Performance of Clinical Chemistry Devices
CLSI EP17-A2: Protocol for Determination of Limits of Detection and Limits of Quantitation; Approved Guideline

# L. Test Principle:

The Phenobarbital assay is a homogeneous particle-enhanced turbidimetric inhibition immunoassay (PETINIA) used for the analysis of phenobarbital in serum or plasma. The assay is based on competition between drug in the sample and drug coated onto a

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microparticle for antibody binding sites of the phenobarbital antibody reagent (mouse). The phenobarbital-coated microparticle reagent is rapidly agglutinated in the presence of the anti-phenobarbital antibody reagent and in the absence of any competing drug in the sample. The rate of absorbance change is measured photometrically, and is directly proportional to the rate of agglutination of the particles. When a sample containing phenobarbital is added, the agglutination reaction is partially inhibited, slowing down the rate of absorbance change. A concentration dependent classic agglutination inhibition curve can be obtained, with maximum rate of agglutination at the lowest phenobarbital concentration and the lowest agglutination rate at the highest phenobarbital concentration.

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

Performance was established on the Abbott ARCHITECT c8000 Clinical Chemistry Analyzer. The data summarized below is the data generated on the ARCHITECT c8000 System.

## 1. Analytical performance:

### a. Precision/Reproducibility:

The inter-assay precision study was performed on one Abbott ARCHITECT c8000 systems clinical analyzer with two reagent lots. Three serum based control levels and 6 serum samples (pooled patient serum samples and negative serum pools spiked with phenobarbital concentrations at 5 levels (5, 10, 20, 40 and 80μg/ml)) were used for the precision study. Each phenobarbital sample was assayed in replicates of two, twice a day for 20 days for a total of 40 runs resulting in a total of 80 replicates for each instrument/lot. Results are summarized below.

Abbott Phenobarbital Assay: Precision

| Sample | Instrument/Reagent Lot | Mean (μg/mL) | Within Run | | Total | |
| --- | --- | --- | --- | --- | --- | --- |
| | | | SD | %CV | SD | %CV |
| Level 1 | 1 | 4.06 | 0.07 | 1.7 | 0.18 | 4.3 |
| | 2 | 4.37 | 0.13 | 3.0 | 0.28 | 6.4 |
| Level 2 | 1 | 9.29 | 0.11 | 0.33 | 0.76 | 1.2 |
| | 2 | 9.62 | 0.16 | 1.6 | 0.23 | 2.4 |
| Level 3 | 1 | 24.02 | 0.33 | 1.4 | 0.52 | 2.2 |
| | 2 | 24.57 | 0.32 | 1.3 | 0.62 | 2.5 |
| Level 4 | 1 | 48.79 | 0.79 | 1.6 | 1.33 | 2.7 |
| | 2 | 46.80 | 0.51 | 1.1 | 1.34 | 2.9 |
| Level 5 | 1 | 74.29 | 1.20 | 1.6 | 1.96 | 2.6 |
| | 2 | 73.09 | 0.70 | 1.0 | 2.76 | 3.8 |
| Patient 1 | 1 | 2.51 | 0.08 | 3.3 | 0.12 | 4.9 |
| | 2 | 2.62 | 0.06 | 2.4 | 0.15 | 5.7 |
| Patient 2 | 1 | 4.35 | 0.09 | 2.0 | 0.15 | 3.5 |
| | 2 | 4.60 | 0.15 | 3.3 | 0.23 | 5.0 |
| Patient 3 | 1 | 11.01 | 0.12 | 1.1 | 0.73 | 6.7 |
| | 2 | 10.89 | 0.17 | 1.6 | 0.25 | 2.2 |
| Patient 4 | 1 | 25.93 | 0.31 | 1.2 | 0.79 | 3.1 |

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| | 2 | 26.71 | 0.42 | 1.6 | 0.68 | 2.5 |
| --- | --- | --- | --- | --- | --- | --- |
| Patient 5 | 1 | 47.72 | 1.01 | 2.1 | 1.44 | 3.0 |
| | 2 | 45.78 | 0.33 | 0.7 | 1.33 | 2.9 |
| Patient 6 | 1 | 77.22 | 1.00 | 1.3 | 1.34 | 1.7 |
| | 2 | 75.70 | 0.67 | 0.9 | 1.97 | 2.6 |

An additional precision study was performed at an external site on one lot of reagents to confirm the observed precision with spiked samples.

| Sample | Mean (μg/mL) | Within Run | | Total | |
| --- | --- | --- | --- | --- | --- |
| | | SD | %CV | SD | %CV |
| Level 1 | 4.10 | 0.07 | 1.8 | 0.183 | 4.5 |
| Level 2 | 9.83 | 0.18 | 1.8 | 0.230 | 2.3 |
| Level 3 | 23.65 | 0.34 | 1.4 | 0.513 | 2.2 |
| Level 4 | 54.59 | 1.44 | 2.6 | 1.82 | 3.3 |
| Level 5 | 77.03 | 1.00 | 1.3 | 1.57 | 2.0 |

# b. Linearity/assay reportable range:

The claimed assay range is $2.0\mu \mathrm{g / mL}$ to $80.0\mu \mathrm{g / mL}$ . The high sample contained human serum spiked with a phenobarbital reference standard. The high sample was diluted with negative serum for 10 concentrations across the entire assay range (and included samples extending above and below the assay range). Each dilution was tested in replicates of four. Regression analysis of each dilution showed that the samples were linear throughout the claimed range ( $y = 1.0555x - 0.5813$ , $R^2 = 0.998$ ).

The recovery of all serum samples relative to the expected concentration based on the standard material and dilution factors, ranged between $92.7 - 109.4\%$

# c. Traceability, Stability, Expected values (controls, calibrators, or methods):

The calibrators used in this submission were cleared under k120936. The controls used in this submission were cleared under k032826.

# d. Detection limit:

CLSI EP17-A2 was followed to determine the limit of blank (LoB). The samples were run with two lots of reagents on one instrument. Testing consisted of 4 replicates of five phenobarbital-free human serum samples tested each day for 3 days. Calculations were performed according to CLSI EP17-A2. The LoB was determined at $0.29\mu \mathrm{g / mL}$

CLSI EP17-A2 was followed to determine the limit of detection (LoD). The Samples were run with two lots of reagents on one instrument. Testing consisted of 4

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replicates of six low level samples at phenobarbital concentrations of 0.25, 0.50, 0.82, 1.21, 1.61 and 2.00μg/mL tested each day per day for 3 days. The LoD was determined at 0.41μg/mL.

CLSI EP17-A2 was followed to determine the limit of quantitation (LoQ). The samples were run with two lots of reagents. Testing consisted of 3 replicates of five low level samples at phenobarbital concentrations of 0.25, 0.50, 1.00, 2.50 and 5.00μg/mL tested twice per day for 7 days. Results from one lot of reagents yielded bias (SD) ≤ 0.12 ug/mL when these five samples were compared to the reference value. LoQ is based on an inter-assay precision of 7% CV at 2.0 ug/ml. The sponsor concluded that LoQ is 2.0 ug/mL.

| LoQ (ug/mL) | Measuring Range (ug/mL) |
| --- | --- |
| 2.0 | 2.0-80 |

e. Analytical specificity:

Serum samples spiked with two levels of phenobarbital near the upper and lower therapeutic ranges were supplemented with the below interfering compounds. Each test and control sample were run in duplicates and the percent cross reactivity (% cross reactivity) was calculated (Measured concentration minus Expected concentration) divided by Drug Concentration Tested multiplied by 100. All % recovery results were within 100%±10%.

Abbott Phenobarbital Assay: Cross Reactivity

| Compound | Test Conc (μg/mL) | % Cross reactivity |
| --- | --- | --- |
| Amitriptyline | 25 | 0.3 |
| Amobarbital | 30 | 2.9 |
| Butabarbital | 100 | -0.1 |
| Carbamazepine | 500 | 0.0 |
| Carbamazepine-10,11-epoxide | 500 | 0.0 |
| Chlordiazepoxide | 500 | 0.0 |
| Chlorpromazine | 60 | -0.2 |
| Clorazepate | 500 | 0.0 |
| Diazepam | 60 | 0.2 |
| Ethosuximide | 500 | 0.0 |
| Ethotoin | 200 | 0.1 |
| 5-Ethyl-5-phenylhydantoin (Nirvanol) | 200 | 0.4 |
| Glutethimide | 200 | 0.1 |
| 5-9p-Hydroxyphenyl)-5-phenylhydantoin | 100 | 0.2 |
| Imipramine | 5 | 4.3 |

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The sponsor also conducted an interference study to evaluate the effects of the following compounds and concentrations with their phenobarbital assay. All samples in this evaluation recovered within $\pm 10\%$ of the expected phenobarbital value.

| Compound | Concentration (μg/mL) | % Recovery |
| --- | --- | --- |
| Bilirubin, unconjugated | 60mg/dL | 100.1 |
| Bilirubin, conjugated | 30mg/mL | 102.1 |
| Hemoglobin | 800mg/dL | 100.0 |
| Triglyceride | 1250mg/dL | 94.8 |
| Cholesterol | 500mg/dL | 109.7 |
| Human serum albumin (HSA) | 7.5g/dL | 99.0 |
| γ-Globulin (IgG) | 12g/dL | 97.0 |
| HAMA | 400ng/mL | 100.7 |
| Rheumatoid Factor (RF) | 500IU/mL | 93.6 |

f. Assay cut-off:

Not applicable

2. Comparison studies:

a. Method comparison with predicate device:

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The Phenobarbital assay (On-test) for the ARCHITECT c8000 System was compared to the Abbott Aeroset® Phenobarbital Assay by testing 118 serum specimens commercially obtained (all natural) with phenobarbital concentrations ranging from 5 to 80ug/mL. Correlation studies were performed using a modified CLSI guideline EP9-A2 and analysis was based on a single measurement of each sample. Results are summarized below.

| Comparative Methods | N | Passing-Bablok | | R |
| --- | --- | --- | --- | --- |
| | | Slope (95% CI) | Intercept (95% CI) | |
| On-test vs Abbott | 118 | 1.003 (0.981-1.022) | 0.363 (-0.106-0.981) | 0.9949 |

## b. Matrix comparison:

The suitability of additional matrices, anticoagulants, or collection tubes was evaluated using drug-free paired donor samples to compare serum in glass (method used in method comparison) with the matrices listed below. Twenty-two to twenty-five samples were spiked with phenobarbital into each paired matrix sample at multiple concentrations spanning the assay range. A singlet set of data was evaluated and the slope, intercept and correlation coefficient determined.

| Comparative Method | N | Range | Deming's Regression | | R |
| --- | --- | --- | --- | --- | --- |
| | | | Slope | Intercept | |
| X: Serum in glass | 25 | 4.14 – 76.26 | 0.982 | 0.189 | 0.9989 |
| Y: Serum in plastic | | | | | |
| X: Serum in glass | 25 | 4.14 - 76.26 | 0.982 | 0.189 | 0.9989 |
| Y: SST | | | | | |
| X: Serum in glass | 22 | 5.52 – 77.98 | 1.022 | -0.425 | 0.9988 |
| Y: Plasma w/NaF/K Oxalate | | | | | |
| X: Serum in glass | 25 | 3.64- 71.50 | 0.984 | 0.389 | 0.9975 |
| Y: Plasma w/Na Heparin in glass | | | | | |
| X: Serum in glass | 25 | 4.20 – 77.23 | 0.976 | 0.098 | 0.9962 |
| Y: Plasma w/Na Heparin in plastic | | | | | |
| X: Serum in glass | 25 | 4.48- 71.00 | 0.983 | -0.067 | 0.9986 |
| Y: Plasma w/Li Heparin w/ gel in plastic | | | | | |
| X: Serum in glass | 25 | 4.48- 71.00 | 1.006 | 0.920 | 0.9982 |
| Y: Plasma w/K3 EDTA in glass | | | | | |
| X: Serum in glass | 25 | 4.40 – 75.16 | 1.035 | -0.277 | 0.9985 |
| Y: Plasma w/K3 EDTA in | | | | | |

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| plastic | | | | | |
| --- | --- | --- | --- | --- | --- |
| X: Serum in glass | 25 | 4.40 – 75.16 | 0.991 | 0.318 | 0.9981 |
| Y:Plasma w/K2 EDTA in plastic | | | | | |
| X: Serum in glass | 25 | 4.01 – 72.69 | 1.009 | -0.122 | 0.9984 |
| Y: Plasma w/Na Citrate in Glass | | | | | |
| X: Serum in glass | 25 | 4.01 – 72.69 | 1.027 | -0.274 | 0.9993 |
| Y: Plasma w/ Na Citrate in Plastic | | | | | |

Out of approximately 300 samples tested, greater than 98% of individual samples recoveries were within ±10% of the expected concentration, and no trends were observed.

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: The sponsor has referenced the following expected values from literature¹ in the package insert:

The desired therapeutic effect is usually achieved in the serum concentration range of 15 to 40μg/mL (65 to 172 umol/L). Concentrations of 35 to 80μg/mL (151 to 345umol/L) are associated with slowness, ataxia, and nystagmus. Concentrations of 65 to 117 μg/mL (280 to 504 umol/L) are associated with coma with reflexes. Concentrations of >100 μg/mL (>430 umol/L) are associated with coma without reflexes. For effective treatment, some patients may require serum levels outside these ranges. Therefore, the expected range is provided only as a guide, and individual patient results should be interpreted in light of other clinical signs and symptoms.

1. Goldman L, Ausiello D, editors. Cecil Medicine, 23rd ed. Philadelphia, PA: Elsevier Saunders; 2008:2994.

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N. Proposed Labeling:

The labeling is sufficient and it satisfies the requirements of 21 CFR Part 809.10.

O. Conclusion:

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

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