← Product Code [LFH](/submissions/TX/subpart-d%E2%80%94clinical-toxicology-test-systems/LFH) · K231020

# Alinity c Tricyclic Antidepressants Reagent Kit (K231020)

_Microgenics Corporation · LFH · Nov 17, 2023 · Clinical Toxicology · SESE_

**Canonical URL:** https://fda.innolitics.com/submissions/TX/subpart-d%E2%80%94clinical-toxicology-test-systems/LFH/K231020

## Device Facts

- **Applicant:** Microgenics Corporation
- **Product Code:** [LFH](/submissions/TX/subpart-d%E2%80%94clinical-toxicology-test-systems/LFH.md)
- **Decision Date:** Nov 17, 2023
- **Decision:** SESE
- **Submission Type:** Traditional
- **Regulation:** 21 CFR 862.3910
- **Device Class:** Class 2
- **Review Panel:** Clinical Toxicology

## Indications for Use

The Alinity c Tricyclic Antidepressants Reagent Kit is a homogeneous enzyme immunoassay intended for use in the qualitative and/or semiquantitative determination of the presence of tricyclic antidepressants (TCAs) in human serum or plasma at a cutoff concentration of 300 ng/mL on the Alinity c system in patients suspected of drug overdose. The semiquantitative mode is for the purpose of enabling laboratories to determine an appropriate dilution of the specimen for confirmation by confirmatory method such as Liquid Chromatography/Tandem Mass Spectrometry (LC-MS/MS), or for permitting laboratories to establish control procedures. The assay provides only a preliminary analytical test result. A more specific alternative chemical method must be used to obtain a confirmed analytical result. Liquid Chromatography/Tandem Mass Spectrometry (LC-MS/MS) is the preferred confirmatory method. Clinical and professional judgment should be applied to any drug of abuse test result, particularly when preliminary positive results are used. For In Vitro Diagnostic Use Only.

## Device Story

Automated clinical chemistry assay; homogeneous enzyme immunoassay (HEIA). Inputs: human serum or plasma samples. Principle: competition between enzyme-labeled drug (G6PDH-nortriptyline) and sample drug for fixed antibody binding sites; enzyme activity inhibited by antibody binding; activity measured spectrophotometrically at 340/416 nm. Output: qualitative (positive/negative) or semiquantitative (concentration) result. Used in clinical laboratories; operated by trained professionals. Provides preliminary analytical results; requires confirmation by LC-MS/MS. Assists clinicians in managing suspected drug overdose cases.

## Clinical Evidence

No clinical data. Performance established via bench testing, including precision (repeatability/reproducibility), linearity, spike recovery, and method comparison against LC-MS/MS using 100 patient samples (50 negative, 50 positive). Interference studies evaluated cross-reactivity with structurally related compounds and potential interference from endogenous/exogenous substances.

## Technological Characteristics

Homogeneous enzyme immunoassay; liquid ready-to-use reagents. R1: sheep polyclonal anti-tricyclics antibodies, G6P, NAD. R2: G6PDH labeled with nortriptyline. Detection: spectrophotometric (340/416 nm). Analyzers: Alinity c system. Storage: 2-8 °C.

## Regulatory Identification

A tricyclic antidepressant drugs test system is a device intended to measure any of the tricyclic antidepressant drugs in serum. The tricyclic antidepressant drugs include imipramine, desipramine, amitriptyline, nortriptyline, protriptyline, and doxepin. Measurements obtained by this device are used in the diagnosis and treatment of chronic depression to ensure appropriate therapy.

## Special Controls

*Classification.* Class II (special controls). A tricyclic antidepressant drugs test system is not exempt if it is intended for any use other than employment or insurance testing or is intended for Federal drug testing programs. 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, provided the test system is intended for employment and insurance testing and includes a statement in the labeling that the device is intended solely for use in employment and insurance testing, and does not include devices intended for Federal drug testing programs (*e.g.,* programs run by the Substance Abuse and Mental Health Services Administration (SAMHSA), the Department of Transportation (DOT), and the U.S. military).

## Predicate Devices

- DRI Tricyclics Serum Tox Assay ([K213875](/device/K213875.md))

## Submission Summary (Full Text)

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FDA

U.S. FOOD & DRUG

ADMINISTRATION

# 510(k) SUBSTANTIAL EQUIVALENCE DETERMINATION DECISION SUMMARY

ASSAY ONLY

## I Background Information:

A 510(k) Number

K231020

B Applicant

Microgenics Corporation

C Proprietary and Established Names

Alinity c Tricyclic Antidepressants Reagent Kit

D Regulatory Information

|  Product Code(s) | Classification | Regulation Section | Panel  |
| --- | --- | --- | --- |
|  LFH | Class II | 21 CFR 862.3910 - Tricyclic Antidepressant Drugs Test System | TX - Clinical Toxicology  |

## II Submission/Device Overview:

A Purpose for Submission:

New device

B Measurand:

Tricyclic antidepressants

C Type of Test:

Qualitative and Semiquantitative Enzyme Immunoassay

## III Intended Use/Indications for Use:

Food and Drug Administration

10903 New Hampshire Avenue

Silver Spring, MD 20993-0002

www.fda.gov

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K231020 - Page 2 of 16

A Intended Use(s):

See Indications for Use below.

B Indication(s) for Use:

The Alinity c Tricyclic Antidepressants Reagent Kit is a homogeneous enzyme immunoassay intended for use in the qualitative and/or semiquantitative determination of the presence of tricyclic antidepressants (TCAs) in human serum or plasma at a cutoff concentration of 300 ng/mL on the Alinity c system in patients suspected of drug overdose.

The semiquantitative mode is for the purpose of enabling laboratories to determine an appropriate dilution of the specimen for confirmation by confirmatory method such as Liquid Chromatography/Tandem Mass Spectrometry (LC-MS/MS), or for permitting laboratories to establish control procedures.

The assay provides only a preliminary analytical test result. A more specific alternative chemical method must be used to obtain a confirmed analytical result. Liquid Chromatography/Tandem Mass Spectrometry (LC-MS/MS) is the preferred confirmatory method.

Clinical and professional judgment should be applied to any drug of abuse test result, particularly when preliminary positive results are used.

For In Vitro Diagnostic Use Only.

C Special Conditions for Use Statement(s):

Rx - For Prescription Use Only

D Special Instrument Requirements:

Abbott Laboratories Alinity c System

IV Device/System Characteristics:

A Device Description:

The Alinity c Tricyclic Antidepressants Reagent Kit is an enzyme immunoassay using the following ready-to-use liquid reagents.

The Alinity c Tricyclic Antidepressants Reagent Kit is supplied as a two liquid reagent kit (R1 and R2). They are included within the same kit, as follows:

- Antibody/Substrate Reagent (R1): Contains polyclonal anti-tricyclics antibodies (sheep), glucose-6-phosphate (G6P), and nicotinamide adenine dinucleotide (NAD) in Tris buffer with sodium azide as a preservative.
- Enzyme Conjugate Reagent (R2): Contains glucose-6-phosphate dehydrogenase (G6PDH) labeled with nortriptyline in Tris buffer with sodium azide as a preservative.

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B Principle of Operation:

The assay is based on the competition between an enzyme-labeled drug and the drug from the serum or plasma for a fixed number of specific antibody binding sites. In the absence of drug from the sample, the specific antibody binds to the drug labeled with glucose-6-phosphate dehydrogenase (G6PDH) and the enzyme activity is inhibited. This phenomenon creates a direct relationship between the drug concentration in the serum or plasma and the enzyme activity. The G6PDH enzyme activity is determined spectrophotometrically at 340/416 nm by measuring its ability to convert nicotinamide adenine dinucleotide (NAD) to NADH.

V Substantial Equivalence Information:

A Predicate Device Name(s):

DRI Tricyclics Serum Tox Assay

B Predicate 510(k) Number(s):

K213875

C Comparison with Predicate(s):

|  Device & Predicate Device(s): | K231020 | K213875  |
| --- | --- | --- |
|  Device Trade Name | Alinity c Tricyclic Antidepressants Reagent Kit | DRI Tricyclics Serum Tox Assay  |
|  General Device Characteristic Similarities |  |   |
|  Intended Use/Indications For Use | Homogeneous enzyme immunoassay intended for use in the qualitative and/or semiquantitative determination of the presence of tricyclic antidepressants (TCAs) in human serum or plasma at a cutoff concentration of 300 ng/mL in patients suspected of drug overdose. | Same  |
|  Calibrator Drug | Nortriptyline | Same  |
|  Cutoff | 300 ng/mL | Same  |
|  Methodology | Homogeneous Enzyme Immunoassay | Same  |
|  Antibody | Sheep polyclonal antibodies | Same  |
|  General Device Characteristic Differences |  |   |
|  Matrix | Serum, Plasma | Serum, Plasma, Urine  |
|  Calibrator Levels for Semi-Quant | 4-point Calibrator | 5-point Calibrator  |

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VI Standards/Guidance Documents Referenced:

CLSI EP05-A3 – Evaluation of Precision of Quantitative Measurement Procedures; Approved Guideline – Third Edition.

CLSI EP06- Ed2– Evaluation of the Linearity of Quantitative Measurement Procedures: - Second Edition

CLSI EP07 – Interference Testing in Clinical Chemistry; Approved Guideline – Third Edition.

CLSI EP09c-A3 – Measurement Procedure Comparison and Bias Estimation Using Patient Samples; Approved Guideline – Third Edition

CLSI EP12-A2 – User Protocol for Evaluation of Qualitative Test Performance; Approved Guideline – Second Edition

CLSI EP25-A – Evaluation of Stability of In Vitro Diagnostic Reagents; Approved Guideline

CLSI-EP35 – Assessment of Equivalence or Suitability of Specimen Types for Medical Laboratory Measurement Procedures.

CLSI-EP37- Supplemental Tables for Interference Testing in Clinical Chemistry - First Edition

CLSI-EP39 Ed-1A- A Hierarchical Approach to Selecting Surrogate Samples for the Evaluation of In Vitro Medical Laboratory Tests – First Edition

VII Performance Characteristics (if/when applicable):

A Analytical Performance:

All analytical performance evaluations were performed on the Abbott Laboratories Alinity c System

1. Precision/Reproducibility:

Precision samples were prepared by spiking nortriptyline into drug-free serum to final concentrations of -100%, -75%, -50%, and -25% below cutoff, cutoff and +25%, +50%, +75%, and +100% above the cutoff, and the target concentrations were confirmed by LC-MS/MS.

The repeatability testing was conducted at one site over 20 days with two runs per day, two replicates per run, on one instrument, in both qualitative and semi-quantitative modes, for a total of 80 results (n=80).

The reproducibility testing was conducted at one site over 5 days with one run per day, five replicates per run, on three instruments, in both qualitative and semi-quantitative modes, for a total of 75 results (n=75).

K231020 - Page 4 of 16

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The results are presented in the tables below:

Repeatability - Qualitative mode:

|  Spiked Conc. (ng/mL) | # of Determinants | # Negative / # Positive  |
| --- | --- | --- |
|  0 | 80 | 80/0  |
|  75 | 80 | 80/0  |
|  150 | 80 | 80/0  |
|  225 | 80 | 80/0  |
|  300 | 80 | 54/26  |
|  375 | 80 | 0/80  |
|  450 | 80 | 0/80  |
|  525 | 80 | 0/80  |
|  600 | 80 | 0/80  |

Repeatability - Semi-quantitative mode

|  Spiked Conc. (ng/mL) | # of Determinants | # Negative / # Positive | Within-run CV | Total-run CV  |
| --- | --- | --- | --- | --- |
|  0 | 80 | 80/0 | N/A | N/A  |
|  75 | 80 | 80/0 | 4.71% | 7.31%  |
|  150 | 80 | 80/0 | 1.61% | 3.31%  |
|  225 | 80 | 80/0 | 1.54% | 2.21%  |
|  300 | 80 | 56/24 | 3.52% | 4.66%  |
|  375 | 80 | 0/80 | 2.91% | 5.60%  |
|  450 | 80 | 0/80 | 2.51% | 4.29%  |

Repeatability testing was also conducted at one site over 20 days with two runs per day, two replicates per run, on one instrument, in the semi-quantitative mode for samples of 525 ng/mL and 600 ng/mL, for a total of 80 results (n=80). No discrepant results were observed.

Reproducibility - Qualitative mode:

|  Spiked Concentration (ng/mL) | % of Cutoff | # of Determinants | Qualitative Immunoassay Results (Negative/Positive)  |
| --- | --- | --- | --- |
|  0 | -100 | 75 | 75/0  |
|  75 | -75 | 75 | 75/0  |
|  150 | -50 | 75 | 75/0  |
|  225 | -25 | 75 | 75/0  |
|  300 | 100 | 75 | 40/35  |
|  375 | +25 | 75 | 0/75  |
|  450 | +50 | 75 | 0/75  |
|  525 | +75 | 75 | 0/75  |
|  600 | +100 | 75 | 0/75  |

K231020 - Page 5 of 16

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Reproducibility - Semi-quantitative mode:

|  Spiked Concentration (ng/mL) | % of Cutoff | # of Determinants | Semi-quantitative Immunoassay Results (Negative/Positive) | Semi-quantitative Reproducibility %CV Results  |
| --- | --- | --- | --- | --- |
|  0 | -100 | 75 | 75/0 | N/A  |
|  75 | -75 | 75 | 75/0 | 4.80%  |
|  150 | -50 | 75 | 75/0 | 2.60%  |
|  225 | -25 | 75 | 75/0 | 1.95%  |
|  300 | 100 | 75 | 49/26 | 2.95%  |
|  375 | +25 | 75 | 0/75 | 5.86%  |
|  450 | +50 | 75 | 0/75 | 3.95%  |

Reproducibility testing was conducted at one site over 5 days with one run per day, five replicates per run, on three instruments, in the semi-quantitative mode for samples of 525 ng/mL and 600 ng/mL, for a total of 75 results (n=75). No discrepant results were observed.

2. Linearity:

Spike Recovery

A spike recovery study was performed at one site with one analyzer. Twenty (20) replicates were run in qualitative mode and semiquantitative mode. One (1) reagent lot, one (1) calibrator lot and one (1) control lot was used.

The study samples were prepared by spiking nortriptyline into drug free serum at concentrations of 225, 300, and 375 ng/mL. No discrepant results were observed in qualitative mode. Results for the semi-quantitative mode are shown in the tables below:

Spike Recovery - Semi-quantitative mode

|  Replicates | 225 ng/mL (n=20) | 300 ng/mL (n=20) | 375 ng/mL (n=20)  |
| --- | --- | --- | --- |
|  Average (ng/mL) | 241.7 | 297.5 | 384.5  |
|  SD | 6.0 | 5.0 | 16.6  |
|  % Recovery from Target | 107.4% | 99.2% | 102.5%  |

K231020 - Page 6 of 16

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K231020 - Page 7 of 16

# Linearity

A linearity study was performed in which drug-free serum was spiked with nortriptyline at the concentration of the high calibrator and then diluted with drug-free serum to generate 9 intermediate levels.

Five (5) replicates of each sample using one (1) lot of reagent, calibrator, and control were run in semi-quantitative mode and the average was used to determine percent recovery compared to the expected target value. The results are presented in the table below:

Linearity - Semi-quantitative mode

|  Level # | Expected concentration (ng/mL) | Average of observed concentration (ng/mL) (N=5) | Mean Recovery (%)  |
| --- | --- | --- | --- |
|  1 | 0 | 5 | N/A  |
|  2 | 62.5 | 74 | 118  |
|  3 | 125.0 | 144 | 115  |
|  4 | 187.5 | 210 | 112  |
|  5 | 250.0 | 260 | 104  |
|  6 | 312.5 | 310 | 99  |
|  7 | 375.0 | 393 | 105  |
|  8 | 437.5 | 453 | 104  |
|  9 | 500 | 492 | 98  |

3. Analytical Specificity/Interference:

## Specificity (Cross-Reactivity)

A specificity (cross-reactivity) study was performed using one lot of reagents, calibrators, and controls.

Test samples were prepared by spiking the potentially cross-reacting compounds at the concentrations in the table below into drug-free serum. The test samples were run in duplicate on one analyzer in the semi-quantitative mode. The cross-reactivity was then calculated from the semi-quantitative result.

The results are summarized in the tables below.

Cross Reactivity to structurally related compounds (TCA and its metabolites)

|  Compound | Tested Concentration (ng/mL) | Cross-reactivity (%)  |
| --- | --- | --- |
|  2-Hydroxy imipramine | 1300 | 23.1%  |
|  7-Hydroxy quetiapine | 100,000 | < 0.3%  |

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K231020 - Page 8 of 16

|  Compound | Tested Concentration (ng/mL) | Cross-reactivity (%)  |
| --- | --- | --- |
|  7-Hydroxy amoxapine solution | 100,000 | < 0.3%  |
|  8-Hydroxy amoxapine solution | 100,000 | < 0.3%  |
|  10-Hydroxyamitriptyline | 1100 | 27.3%  |
|  Amitriptyline | 300 | 100%  |
|  Amoxapine | 200,000 | 0.15%  |
|  Clomipramine | 325 | 92.3%  |
|  Desipramine | 280 | 107.1%  |
|  Dosulepin | 500 | 60.0%  |
|  Doxepin | 600 | 50.0%  |
|  Imipramine | 190 | 157.9%  |
|  Lofepramine | 440 | 68.1%  |
|  N-Desmethyltrimipramine | 325 | 92.3%  |
|  Norclomipramine hydrochloride | 375 | 80.0%  |
|  Nordoxepin hydrochloride | 2000 | 15.0%  |
|  Nortriptyline | 300 | 100.0%  |
|  Opipramol HCl | 350 | 85.7%  |
|  Protriptyline | 500 | 60.0%  |
|  Quetiapine fumarate | 55,000 | 0.54%  |
|  Trimipramine | 400 | 75.0%  |

Cross Reactivity to other structurally related compounds

|  Compound | Tested Concentration (ng/mL) | Cross-reactivity (%)  |
| --- | --- | --- |
|  Alimemazine | 10,000 | 3.0%  |
|  Blonanserin | 100,000 | < 0.3%  |

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K231020 - Page 9 of 16
|  Compound | Tested Concentration (ng/mL) | Cross-reactivity (%)  |
| --- | --- | --- |
|  Chlorpromazine | 500 | 60.0%  |
|  Clozapine | 100,000 | < 0.3%  |
|  Cyclobenzaprine | 375 | 80.0%  |
|  Desloratadine | 100,000 | < 0.3%  |
|  Diphenhydramine | 60,000 | 0.5%  |
|  Fluoxetine | 100,000 | < 0.3%  |
|  Fluphenazine | 2000 | 15.0%  |
|  Haloperidol | 100,000 | < 0.3%  |
|  Loratadine | 100,000 | < 0.3%  |
|  Loxapine succinate | 100,000 | < 0.3%  |
|  Maprotiline | 100,000 | 0.3%  |
|  Mianserin | 100,000 | < 0.3%  |
|  Mirtazapine | 100,000 | < 0.3%  |
|  N-desmethylclozapine | 100,000 | < 0.3%  |
|  Nefazodone | 100,000 | < 0.3%  |
|  N-Desmethylmirtazapine | 100,000 | < 0.3%  |
|  Normaprotiline | 100,000 | 0.3%  |
|  Olanzapine | 100,000 | < 0.3%  |
|  Paroxetine | 100,000 | < 0.3%  |
|  Perphenazine | 450 | 66.7%  |
|  Phenoxybenzamine | 100,000 | < 0.3%  |
|  Promazine | 450 | 66.7%  |
|  Promethazine | 20,000 | 1.5%  |
|  Risperidone | 100,000 | < 0.3%  |
|  Sertraline | 100,000 | < 0.3%  |
|  Thioridazine | 5000 | 6.0%  |

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The sponsor also performed a study in which structurally unrelated compounds were spiked into samples containing TCA concentrations above and below the cutoff to evaluate the potential for positive or negative interference from these compounds. The results are presented in the table below.

|  Compound | Tested Concentration (ng/mL) | Compound Spiked into Low Sample (225 ng/mL) | Compound Spiked into High Sample (375 ng/mL)  |
| --- | --- | --- | --- |
|  11-nor-Δ9-THC-COOH | 100,000 | Negative | Positive  |
|  6-Acetyl morphine | 75,000 | Negative | Positive  |
|  Acetaminophen | 100,000 | Negative | Positive  |
|  Acetylsalicylic acid | 100,000 | Negative | Positive  |
|  Amisulpride | 100,000 | Negative | Positive  |
|  Amoxicillin | 100,000 | Negative | Positive  |
|  Amphetamine | 100,000 | Negative | Positive  |
|  Benzotropine methane sulfonate | 3000 | Negative | Positive  |
|  Benzoylecgonine | 100,000 | Negative | Positive  |
|  Brompheniramine | 3000 | Negative | Positive  |
|  Caffeine | 100,000 | Negative | Positive  |
|  Carbamazepine* | 3000 | Negative | Positive  |
|  Carbamazepine epoxide | 10,000 | Negative | Positive  |
|  Chloroquine phosphate | 100,000 | Negative | Positive  |
|  Cimetidine | 100,000 | Negative | Positive  |

K231020 - Page 10 of 16

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|  Compound | Tested Concentration (ng/mL) | Compound Spiked into Low Sample (225 ng/mL) | Compound Spiked into High Sample (375 ng/mL)  |
| --- | --- | --- | --- |
|  Cocaine | 75,000 | Negative | Positive  |
|  Codeine | 100,000 | Negative | Positive  |
|  Dextromethorphan | 100,000 | Negative | Positive  |
|  Diacetylmorphine (Heroin) | 100,000 | Negative | Positive  |
|  Diazepam | 100,000 | Negative | Positive  |
|  Digoxin | 100,000 | Negative | Positive  |
|  Dihydrocodeine | 100,000 | Negative | Positive  |
|  EDDP perchlorate | 100,000 | Negative | Positive  |
|  EMDP-HCl | 100,000 | Negative | Positive  |
|  Fentanyl | 25,000 | Negative | Positive  |
|  Glutethimide | 100,000 | Negative | Positive  |
|  Hydrocodone | 100,000 | Negative | Positive  |
|  Hydrocortisone | 100,000 | Negative | Positive  |
|  Hydromorphone | 100,000 | Negative | Positive  |
|  Hydroxyzine | 3000 | Negative | Positive  |
|  Ibuprofen | 100,000 | Negative | Positive  |
|  Levorphanol | 100,000 | Negative | Positive  |
|  Levothyroxine | 100,000 | Negative | Positive  |
|  Meperidine | 25,000 | Negative | Positive  |
|  Methadone | 75,000 | Negative | Positive  |
|  Methamphetamine | 100,000 | Negative | Positive  |
|  Methaqualone | 500 | Negative | Positive  |
|  Methsuximide | 75,000 | Negative | Positive  |
|  Methylphenidate | 100,000 | Negative | Positive  |
|  Morphine | 100,000 | Negative | Positive  |
|  Morphine-3β-glucuronide | 100,000 | Negative | Positive  |

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K231020 - Page 12 of 16
|  Compound | Tested Concentration (ng/mL) | Compound Spiked into Low Sample (225 ng/mL) | Compound Spiked into High Sample (375 ng/mL)  |
| --- | --- | --- | --- |
|  Morphine-6β-glucuronide | 100,000 | Negative | Positive  |
|  Nalbuphine | 100,000 | Negative | Positive  |
|  Nalorphine | 100,000 | Negative | Positive  |
|  Naloxone | 100,000 | Negative | Positive  |
|  Naltrexone | 100,000 | Negative | Positive  |
|  Naproxen | 100,000 | Negative | Positive  |
|  Norcodeine | 100,000 | Negative | Positive  |
|  Nordiazepam | 100,000 | Negative | Positive  |
|  Norethindrone | 100,000 | Negative | Positive  |
|  Norhydrocodone | 100,000 | Negative | Positive  |
|  Noroxycodone | 100,000 | Negative | Positive  |
|  Noroxymorphone | 100,000 | Negative | Positive  |
|  Norpropoxyphene | 75,000 | Negative | Positive  |
|  Oxaprozin | 100,000 | Negative | Positive  |
|  Oxazepam | 100,000 | Negative | Positive  |
|  Oxycodone | 100,000 | Negative | Positive  |
|  Oxymorphone | 100,000 | Negative | Positive  |
|  PCP | 25,000 | Negative | Positive  |
|  Phenobarbital | 100,000 | Negative | Positive  |
|  Phenytoin | 100,000 | Negative | Positive  |
|  Primidone | 100,000 | Negative | Positive  |
|  Procyclidine | 100,000 | Negative | Positive  |
|  Propoxyphene | 100,000 | Negative | Positive  |
|  Secobarbital | 100,000 | Negative | Positive  |
|  Tapentadol | 100,000 | Negative | Positive  |
|  Temazepam | 100,000 | Negative | Positive  |

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K231020 - Page 13 of 16

|  Compound | Tested Concentration (ng/mL) | Compound Spiked into Low Sample (225 ng/mL) | Compound Spiked into High Sample (375 ng/mL)  |
| --- | --- | --- | --- |
|  Triprolidine | 100,000 | Negative | Positive  |
|  Valproic acid | 100,000 | Negative | Positive  |
|  Venlafaxine | 100,000 | Negative | Positive  |
|  Verapamil | 100,000 | Negative | Positive  |

None of the compounds in the table above caused positive or negative interference at the concentrations tested.

*The sponsor performed additional testing and determined that Carbamazepine concentrations of 4000 ng/mL and higher caused positive results at a TCA concentration of 253 ng/mL (approximately 25% below the cutoff concentration of 300 ng/mL).

The sponsor also provided documentation from the literature supporting that Carbamazepine in the presence of TCA will cause a falsely elevated TCA result with some immunoassays. This limitation is included in the sponsor's labeling.

The sponsor also performed a study to evaluate potential positive or negative interference with the candidate assay from common endogenous and exogenous substances. Potentially interfering substances were spiked into the low control, 225 ng/mL (-25% of the cutoff concentration of 300 ng/mL) and high control, 375 ng/mL (+25% of the cutoff concentration of 300 ng/mL).

No positive or negative interference was seen in the presence of the compounds listed in the table below:

|  Compounds | Tested Concentrations (mg/dL) | Low Control (225 ng/mL) | High Control (375 ng/mL)  |
| --- | --- | --- | --- |
|  Bilirubin (Conjugated) | 40 | Negative | Positive  |
|  Bilirubin (Unconjugated) | 40 | Negative | Positive  |
|  Hemoglobin | 1000 | Negative | Positive  |
|  Human Serum Albumin (HSA) | 7500 | Negative | Positive  |
|  γ-globulin | 5000 | Negative | Positive  |
|  Rh Factor | 1300 IU | Negative | Positive  |
|  Triglycerides | 1500 | Negative | Positive  |
|  Cholesterol | 1400 | Negative | Positive  |

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K231020 - Page 14 of 16

4. **Assay Reportable Range:**

The assay reportable range for neat samples extends to 500 ng/mL and higher concentrations will be reported as &gt;500 ng/mL. If a semi-quantitative value greater than 500 ng/mL is required, a 1:5 or 1:10 manual dilution may be performed, as specified in the labeling. The sponsor providing the results of a manual dilution study demonstrating that accurate results could be obtained with 1:5 and 1:10 dilutions.

5. **Traceability, Stability, Expected Values (Controls, Calibrators, or Methods):**

Traceability: The assay is traceable to the certified reference material (nortriptyline purchased from a commercial source).

6. **Detection Limit:**

Not applicable.

7. **Assay Cut-Off:**

Characterization of how the device performs analytically around the claimed cutoff concentration is described in the precision section, VII.A.1. above.

B **Comparison Studies:**

1. **Method Comparison with Predicate Device:**

The sponsor evaluated 50 negative and 50 positive samples in both qualitative and semi-quantitative modes by comparing the results to LC-MS/MS (Liquid chromatography-tandem mass spectroscopy). The testing was performed using one lot of reagents, one lot of calibrators, and one lot of controls.

**Results – Qualitative mode**

|  Alinity TCA Assay Results | Negative by LC-MS/MS | < 50% of Cutoff concentration by LC-MS/MS (< 150 ng/mL) | Near Cutoff Negative (Between 50% below the cutoff and the cutoff concentration as determined by LC-MS/MS) (150-299 ng/mL) | Near Cutoff Positive (Between the cutoff and 50% above the cutoff concentration as determined by LC-MS/MS) (300-450 ng/mL) | High Positives (Greater than 50% above cutoff concentration (> 450 ng/mL)  |
| --- | --- | --- | --- | --- | --- |
|  Positive | 0 | 2* | 0 | 38 | 12  |
|  Negative | 0 | 19 | 29 | 0 | 0  |

{14}

Results – Semiquantitative mode

|  Alinity TCA Assay Results | Negative by LC-MS/MS | < 50% of Cutoff concentration by LC-MS/MS (< 150 ng/mL) | Near Cutoff Negative (Between 50% below the cutoff and the cutoff concentration as determined by LC-MS/MS) (150-299 ng/mL) | Near Cutoff Positive (Between the cutoff and 50% above the cutoff concentration as determined by LC-MS/MS) (300-450 ng/mL) | High Positives (Greater than 50% above cutoff concentration (> 450 ng/mL)  |
| --- | --- | --- | --- | --- | --- |
|  Positive | 0 | 2* | 0 | 38 | 12  |
|  Negative | 0 | 19 | 29 | 0 | 0  |

*these samples detected positive by immunoassay contained Carbamazepine at concentrations of 4275 ng/mL and 5285 ng/mL, respectively. Carbamazepine has been shown to interfere with this immunoassay at these concentrations.

2. Matrix Comparison:

The sponsor performed a study in which patient samples were run in both qualitative and semi-quantitative modes in accordance with CLSI Guidelines EP12-A2, EP35 and EP39. For comparison between serum, K₂ EDTA, K₃ EDTA, and lithium heparin samples, 50 matched samples with concentrations covering the measuring range were analyzed. For the comparison between serum and sodium heparin, a different set of 50 matched samples with concentrations covering the measuring range were analyzed. The study demonstrated that nortriptyline concentrations obtained in different test plasma matrices with different anticoagulants are equivalent to those measured in the primary or control matrix (serum) across the assay’s measuring range. Results are presented in the table below.

|  Serum Matrix | Qualitative |   | Semi- Quantitative  |   |   |
| --- | --- | --- | --- | --- | --- |
|   |   |  Positive | Negative | Positive | Negative  |
|  K2 EDTA Plasma | Positive | 25 | 0 | 25 | 0  |
|   |  Negative | 0 | 25 | 0 | 25  |
|  K3 EDTA plasma | Positive | 25 | 0 | 25 | 0  |
|   |  Negative | 0 | 25 | 0 | 25  |
|  Lithium Heparin Plasma | Positive | 25 | 0 | 25 | 0  |
|   |  Negative | 0 | 25 | 0 | 25  |
|  Sodium Heparin Plasma | Positive | 25 | 0 | 25 | 0  |
|   |  Negative | 0 | 25 | 0 | 25  |

K231020 - Page 15 of 16

{15}

C Clinical Studies:

1. Clinical Sensitivity:
Not applicable.

2. Clinical Specificity:
Not applicable.

3. Other Clinical Supportive Data (When 1. and 2. Are Not Applicable):
Not applicable.

D Clinical Cut-Off:
Not applicable.

E Expected Values/Reference Range:
Not applicable.

VIII Proposed Labeling:
The labeling supports the finding of substantial equivalence for this device.

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

K231020 - Page 16 of 16

---

**Source:** [https://fda.innolitics.com/submissions/TX/subpart-d%E2%80%94clinical-toxicology-test-systems/LFH/K231020](https://fda.innolitics.com/submissions/TX/subpart-d%E2%80%94clinical-toxicology-test-systems/LFH/K231020)

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