Dimension Tacrolimus Flex® Reagent Cartridge (TAC), Dimension Tacrolimus Calibrator (TAC CAL)

K150168 · Siemens Healthcare Diagnostics · MLM · Nov 4, 2015 · Clinical Chemistry

Device Facts

• Record ID: K150168
• Device Name: Dimension Tacrolimus Flex® Reagent Cartridge (TAC), Dimension Tacrolimus Calibrator (TAC CAL)
• Applicant: Siemens Healthcare Diagnostics
• Product Code: MLM · Clinical Chemistry
• Decision Date: Nov 4, 2015
• Decision: SESE
• Submission Type: Traditional
• Regulation: 21 CFR 862.1678
• Device Class: Class 2

Indications for Use

The Dimension Tacrolimus Flex® Reagent Cartridge (TAC) method is an in vitro diagnostic test for the quantitative measurement of tacrolimus in human whole blood on the Dimension® clinical chemistry system. Measurements of tacrolimus are used as an aid in the management of tacrolimus therapy in renal and hepatic transplant patients. The Dimension Tacrolimus Calibrator (TAC CAL) is an in vitro diagnostic product for the calibration of the Tacrolimus (TAC) method on the Dimension® clinical chemistry system.

Device Story

The Dimension® TAC method is an automated, quantitative immunoassay performed on the Dimension® clinical chemistry system. It uses a Flex® reagent cartridge containing pretreatment reagents, antibody-β-galactosidase conjugate, tacrolimus-coated magnetic particles, and CPRG substrate. The device processes EDTA whole blood samples. Tacrolimus in the sample binds to the antibody; free antibody-enzyme conjugate binds to the magnetic particles. After magnetic separation, the supernatant containing the tacrolimus-antibody-enzyme complex is mixed with CPRG. β-galactosidase catalyzes the hydrolysis of CPRG to produce chlorophenol red, which is measured spectrophotometrically at 577 nm. The rate of absorbance change is directly proportional to tacrolimus concentration. The system provides flags for processing errors. Results assist clinicians in managing immunosuppressive therapy. The device includes a five-level liquid calibrator for method calibration. It is intended for use in clinical laboratories.

Clinical Evidence

Bench testing only. Precision (CLSI EP5-A2) showed repeatability ≤6.6% CV, within-lab ≤13.1% CV. Linearity (CLSI EP06-A) established 1.0-30.0 ng/mL range. Specificity (CLSI EP7-A2) evaluated cross-reactivity with major/minor/second-pass metabolites and co-administered drugs. Method comparison (CLSI EP9-A2) with 315 samples (vs LC-MS/MS) and 308 samples (vs ARCHITECT) showed strong correlation (r=0.966 and r=0.979 respectively).

Technological Characteristics

Immunoassay using magnetic particles (chromium dioxide) and antibody-beta-galactosidase conjugate. Substrate: chlorophenol red beta-d-galactopyranoside (CPRG). Measurement: bichromatic rate (577/700 nm). Form factor: 8-well Flex® Reagent Cartridge. System: Dimension® clinical chemistry system. Calibrator: 5-level frozen liquid whole blood hemolysate.

Indications for Use

Indicated for renal and hepatic transplant patients requiring quantitative measurement of tacrolimus in human whole blood to aid in therapy management. Prescription use only.

Regulatory Classification

Identification

A tacrolimus test system is a device intended to quantitatively determine tacrolimus concentrations as an aid in the management of transplant patients receiving therapy with this drug. This generic type of device includes immunoassays and chromatographic assays for tacrolimus.

Special Controls

*Classification.* Class II (special controls). The special control is “Class II Special Controls Guidance Document: Cyclosporine and Tacrolimus Assays; Guidance for Industry and FDA.” See § 862.1(d) for the availability of this guidance document.

Predicate Devices

• Abbott® ARCHITECT Tacrolimus Test System (k070820)
• Dimension® Tacrolimus Calibrator (k060503)

Reference Devices

• LC/MS-MS Assay for Tacrolimus
• Dimension® TACR (k060502)

Submission Summary (Full Text)

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

A. 510(k) Number:
k150168

B. Purpose for Submission:
New Device

C. Measurand:
Tacrolimus

D. Type of Test:
Quantitative immunoassay

E. Applicant:
Siemens Healthcare Diagnostics, Inc.

F. Proprietary and Established Names:
Dimension Tacrolimus Flex® Reagent Cartridge (TAC)
Dimension Tacrolimus Calibrator (TAC CAL)

G. Regulatory Information:
1. Regulation section:
21 CFR §862.1678, Tacrolimus Test System
21 CFR §862.1150, Calibrator
2. Classification:
Class II
3. Product code:
MLM, JIT

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4. Panel:

Toxicology (91)

H. Intended Use:

1. Intended use(s):

See indications for use below.

2. Indication(s) for use:

The Dimension Tacrolimus Flex® Reagent Cartridge (TAC) is an in vitro diagnostic test for the quantitative measurement of tacrolimus in human whole blood on the Dimension® clinical chemistry system. Measurements of tacrolimus are used as an aid in the management of tacrolimus therapy in renal and hepatic transplant patients.

The Dimension Tacrolimus Calibrator (TAC CAL) is an in vitro diagnostic product for the calibration of the Tacrolimus (TAC) method on the Dimension® clinical chemistry system.

3. Special conditions for use statement(s):

Prescription use only

The instrument reporting system contains flags and comments to provide the user with information regarding instrument processing errors, instrument status information and potential errors in TAC results. Refer to the Dimension® Operator’s Guide for the meaning of report flags and comments. Any result containing flags and/or comments should be addressed according to your laboratory’s procedure manual.

Patient samples may contain heterophilic antibodies that could react in immunoassays to give falsely elevated or depressed results. Antibodies to β-galactosidase can be encountered in samples as a consequence of bacterial infection and may produce falsely elevated results which may not be consistent with clinical evaluation. The assay has been designed to minimize interference from antibodies to β-galactosidase. In very rare instances, immunoassays may produce falsely elevated or decreased results due to other patient-specific interferents. A number of these interferents are present in the plasma of affected patient samples and will be detected by the automatic rerun procedure. Complete elimination of such interference from all patient specimens cannot be guaranteed. A test result that is inconsistent with the clinical picture and patient history should be interpreted with caution. Confirmation of unexpected or atypical results by an alternative methodology is recommended prior to any adjustments in tacrolimus dosage. For patients with impaired liver function and patients receiving other drugs which may induce or inhibit microsomal enzyme activity, the routine use of the Dimension® Tacrolimus assay may be supported by HPLC data to assess possible changes in biotransformation and elimination.

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If TACR (Cat.No. DF107) and TAC (Cat. No. DF207) assays are processed on the same instrument, there is a remote potential for carryover from the TACR pretreatment reagent to produce falsely elevated results with the TAC assay. This potential has been mitigated as much as possible through the instrument software.

If use of the TAC and TACR assays on the same instrument cannot be avoided, as a further safeguard, each run of the TAC assay should be immediately preceded by flushing the reagent and sample probes (10 cycles) using the Prime Pump routine (SYSTEM PREP, PUMP PRIME, PRIME WATER). TAC reagent hydrations should also be preceded by flushing of the probes using this routine. Laboratories should convert as rapidly as possible to consistent use of the TAC assay for individual patients, discontinue use of the TACR assay and remove any remaining TACR reagent from the instrument inventory.

4. Special instrument requirements:

The Dimension® clinical chemistry system

I. Device Description:

The automated Dimension® TAC method is performed using a method specific Flex® reagent cartridge. The reagents for this assay are packaged in an 8-well Flex® Reagent Cartridge that contains a pretreatment reagents, antibody-β-galactosidase conjugate, tacrolimus immobilized on chromium dioxide particles, chlorophenol red β-d-galactopyranoside (CPRG) substrate, and diluent to hydrate the tablets.

Dimension® Tacrolimus (TAC) Calibrator is five level frozen liquid, whole blood hemolysate containing purified tacrolimus. The product is provided in 4.0 mL vials, 2 vials per level. There are five calibrator levels per kit which span the assay range for the Dimension® Tacrolimus (TAC) assay. The calibrators are packaged at 1.0 mL per vial for levels 2 – 5. Level 1, calibrator base with no tacrolimus has 2.0 mL per vial so that it can also be used as a high sample diluent.

Each level of TAC Calibrator is prepared from human whole blood hemolysate base. Levels 2 – 5 are spiked with purified tacrolimus drug to achieve target concentrations of 3 ± 1 ng/mL; 6 ± 1 ng/mL; 12 ± 2 ng/mL and >30.0 ng/mL. Level 1 calibrator has no drug added.

The calibrator package insert contains the following caution: “Contains human source material. Each donor unit used in the preparation of this product was tested by FDA-approved methods for the presence of antibodies to Human Immunodeficiency Virus Type 1 (HIV-1) and Type 2 (HIV-2), as well as for Hepatitis B surface Antigen and antibody to Hepatitis C Virus (HCV), and found to be negative (not repeatedly reactive). Because no testing can offer complete assurance that these or other infectious agents are absent, this material should be handled using good laboratory practice to avoid skin contact and ingestion”.

J. Substantial Equivalence Information:

1. Predicate device name(s):

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ARCHITECT Tacrolimus Assay

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

k070820

3. Comparison with predicate:

| Item | Device Dimension® TAC Flex® reagent cartridge | Predicate ARCHITECT Tacrolimus Assay (k070820) |
| --- | --- | --- |
| Similarities | | |
| Intended Use | For the quantitative measurement of tacrolimus in human whole blood as an aid in the management of tacrolimus therapy in renal and hepatic transplant patients | Same |
| Assay type | Immunoassay | Same |
| Sample Type | Whole blood in EDTA | Same |
| High Sample Dilution | Manual | Same |
| Differences | | |
| Instrument | The Dimension® clinical chemistry system | The Abbott ARCHITECT i System |
| Sample Pretreatment | No manual pretreatment | Manual pre-treatment |
| Measuring Range | 1.0 – 30 ng/mL | 2 – 30 ng/mL |
| Cross reactivity Profile M-I | 1% | 8% |
| M-II | 18% | 94% |
| M-III | 15% | 45% |
| M-IV | 99% | 9% |
| M-V | 1% | Not Available |
| M-VI | 1% | Not Available |
| M-VII | 43% | Not Available |
| M-VIII | 0% | Not Available |
| Item | Device TAC CAL | Predicate TACR CAL (k060503) |
| --- | --- | --- |
| Similarities | | |
| Intended Use | For the calibration of the Tacrolimus (TAC) method on the Dimension® clinical chemistry system. | Same |
| Form | Frozen Liquid | Same |

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| Matrix | Whole blood hemolysate | Same |
| --- | --- | --- |
| Levels | Five | Same |
| Traceability | Purified tacrolimus | Same |
| Differences | | |
| Assignment | Assigned for Dimension® TAC | Assigned for Dimension® TACR |
| Target Concentration Range | Level 1: -0.5 to +0.5 ng/mL
Level 2: 2.7 to 4.2 ng/mL
Level 3: 5.8 to 7.3 ng/mL
Level 4: 11.6 to 13.6 ng/mL
Level 5: ≥30.0 ng/mL | Level A: -0.7 to +0.7 ng/mL
Level 2: 2.5 to 4.0 ng/mL
Level 3: 5.5 to 7.0 ng/mL
Level 4: 11.0 to 13.0 ng/mL
Level 5: 31.0 to 34.0 ng/mL |

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

- CLSI EP5-A2, Evaluation of Precision Performance of Quantitative Measurement Methods
- CLSI EP06-A, Evaluation of the Linearity of Quantitative Measurement Procedures: A Statistical Approach
- CLSI EP07-A2, Interference Testing in Clinical Chemistry; Approved Guideline-Second Edition
- CLSI EP09-A3, Measurement Procedure Comparison and Bias Estimation Using Patient Samples; Approved GuidelineCLSIEP17-A2,Evaluation of Detection Capability for ClinicalLaboratory Measurement Procedures; Approved Guideline
- FDA Guidance document "Class II Special Controls Guidance Document: Cyclosporine and Tacrolimus Assays; Guidance for Industry and FDA" - 09/16/2002.

# L. Test Principle:

The Dimension® TAC method is an automated immunoassay in which free and tacrolimus-bound antibody-enzyme conjugate is separated using magnetic particles. The tacrolimus present in the sample is bound by the tacrolimus antibody. Magnetic particles coated with tacrolimus are added to bind free (unbound) antibody-enzyme conjugate. The reaction mixture is then separated magnetically. Following separation, the supernatant containing the tacrolimus-antibody-enzyme complex is transferred to a cuvette and mixed with the substrate; chlorophenol red $\beta$ -d-galactopyranoside (CPRG). $\beta$ -galactosidase catalyzes the hydrolysis of CPRG to produce chlorophenol red (CPR) that absorbs light maximally at 577 nm. The change in absorbance at $577~\mathrm{nm}$ due to the formation of CPR is directly proportional to the amount of tacrolimus in the patient's sample and is measured using a bichromatic (577, $700~\mathrm{nm}$ ) rate technique.

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M. Performance Characteristics (if/when applicable):

1. Analytical performance:

a. Precision/Reproducibility:

Precision of the Dimension® TAC method was evaluated at two external testing sites, and at Siemens internal laboratory following EP5-A. Whole blood patient pools and control materials were chosen at concentrations which represented the sub-therapeutic, therapeutic and toxic range of the assay. For each test level, a single test from two independent cups was analyzed twice per day for 20 days (N=80). A single lot of reagent and calibrators was tested at each of the two external sites; whereas two additional lots of reagents were tested at the internal site to evaluate lot-to-lot variability. A whole blood sample with extremely low concentration of Tacrolimus was also tested at the internal site. The results are summarized below:

Internal site

| Material | Mean ng/mL | Repeatability (N=4) | | Total Precision (N=80) | |
| --- | --- | --- | --- | --- | --- |
| | | SD | %CV | SD | %CV |
| Whole Blood Pool #1 | 1.8 | 0.11 | 6.1 | 0.22 | 12.1 |
| Sample | Lot | Mean ng/mL | Repeatability (N=4) | | Total Precision (N=80) | |
| --- | --- | --- | --- | --- | --- | --- |
| | | | SD | %CV | SD | %CV |
| Whole Blood Pool #2 | Lot 1 | 5.9 | 0.19 | 3.2 | 0.23 | 3.8 |
| | Lot 2 | 5.8 | 0.16 | 2.7 | 0.18 | 3.1 |
| | Lot 3 | 6.0 | 0.18 | 3.1 | 0.26 | 4.4 |
| | | | | | | |
| Whole Blood Pool #3 | Lot 1 | 12.9 | 0.41 | 3.2 | 0.54 | 4.2 |
| | Lot 2 | 13.5 | 0.37 | 2.7 | 0.49 | 3.6 |
| | Lot 3 | 14.0 | 0.42 | 3.0 | 0.57 | 4.0 |
| | | | | | | |
| Whole Blood Pool #4 | Lot 1 | 20.2 | 0.65 | 3.2 | 0.84 | 4.2 |
| | Lot 2 | 21.6 | 0.59 | 2.7 | 0.89 | 4.1 |
| | Lot 3 | 21.9 | 0.68 | 3.1 | 0.86 | 3.9 |
| | | | | | | |
| QC Level 1 | Lot 1 | 5.1 | 0.16 | 3.1 | 0.23 | 4.6 |
| | Lot 2 | 5.1 | 0.09 | 1.8 | 0.18 | 3.5 |
| | Lot 3 | 5.2 | 0.18 | 3.5 | 0.20 | 3.9 |
| | | | | | | |
| QC Level 2 | Lot 1 | 11.7 | 0.29 | 2.5 | 0.42 | 3.6 |
| | Lot 2 | 12.2 | 0.33 | 2.7 | 0.48 | 3.9 |
| | Lot 3 | 12.6 | 0.51 | 4.0 | 0.66 | 5.2 |
| | | | | | | |

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| QC Level 3 | Lot 1 | 28.3 | 1.12 | 3.9 | 1.40 | 4.9 |
| --- | --- | --- | --- | --- | --- | --- |
| | Lot 2 | 29.8 | 0.90 | 3.0 | 1.07 | 3.6 |
| | Lot 3 | 29.5 | 0.83 | 2.8 | 1.22 | 4.1 |

External site 1

| Material | Mean ng/mL | Repeatability (N=4) | | Total Precision (N=80) | |
| --- | --- | --- | --- | --- | --- |
| | | SD | %CV | SD | %CV |
| Whole blood Pool 1 | 1.8 | 0.16 | 8.3 | 0.26 | 14.0 |
| Whole blood Pool 2 | 5.4 | 0.16 | 2.9 | 0.34 | 6.3 |
| Whole blood Pool 3 | 13.1 | 0.29 | 2.2 | 0.61 | 4.6 |
| Whole blood Pool 4 | 20.7 | 0.48 | 2.3 | 1.02 | 4.9 |
| OC level 1 | 4.4 | 0.17 | 3.8 | 0.30 | 6.9 |
| OC level 2 | 11.4 | 0.26 | 2.3 | 0.51 | 4.5 |
| OC level 3 | 27.4 | 0.86 | 3.2 | 1.40 | 5.1 |

External site 2

| Material | Mean ng/mL | Repeatability (N=4) | | Total Precision (N=80) | |
| --- | --- | --- | --- | --- | --- |
| | | SD | %CV | SD | %CV |
| Whole Blood Pool 1 | 1.8 | 0.12 | 6.6 | 0.24 | 13.1 |
| Whole Blood Pool 2 | 5.1 | 0.18 | 3.6 | 0.31 | 6.0 |
| Whole Blood Pool 3 | 13.0 | 0.28 | 2.2 | 0.52 | 4.0 |
| Whole Blood Pool 4 | 20.8 | 0.49 | 2.4 | 0.96 | 4.6 |
| OC level 1 | 4.3 | 0.14 | 3.3 | 0.23 | 5.3 |
| OC level 2 | 11.6 | 0.30 | 2.6 | 0.49 | 4.2 |
| OC level 3 | 28.7 | 0.88 | 3.1 | 1.63 | 5.7 |

b. Linearity/assay reportable range:

Linearity

A high tacrolimus native patient pool (40.6 ng/mL) and a patient pool with no tacrolimus were combined in different ratios to produce nine levels of patient pools which bracketed both the high and low end of the proposed assay range. The expected concentrations of the samples based on the dilution factors are 0.0, 5.1, 10.2, 15.2, 20.3, 25.4, 30.5, 35.6, 40.6 ng/mL. All nine pools were assayed in replicate of 4 on a single Dimension® analyzer. The measured values (Y) were compared to the expected values (X). The result of linear regression based on each replicate is summarized in the below table. The results below support the proposed measuring range of 1.0 – 30.0 ng/mL.

| | Rep 1 | Rep 2 | Rep 3 | Rep 4 |
| --- | --- | --- | --- | --- |
| Slope | 1.021 | 1.011 | 1.016 | 1.025 |
| Intercept | -0.12 | +0.21 | +0.16 | +0.12 |
| Correlation Coefficient | 0.999 | 0.995 | 0.996 | 0.997 |

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# Spiked recovery

Recovery of tacrolimus by the Dimension TAC assay was determined by adding a known amount of USP standard tacrolimus to five human blood pools from patients receiving tacrolimus therapy. The results for the samples spiked with tacrolimus were compared to the control samples and the recovery was calculated using mean of 10 replicates of each sample. The sponsor defined acceptance criterion is $90 - 110\%$ recovery of the expected value.

The results are summarized in the table below.

Dimension TAC - Spiked Recovery

| Tacrolimus spiked amount (ng/mL) | Avg % Recovery | Range of % Recovery |
| --- | --- | --- |
| 4.2 | 96% | 93-98% |
| 7.2 | 95% | 92-99% |
| 8.3 | 94% | 90-96% |
| 10.7 | 103% | 97-111% |
| 11.6 | 98% | 92-103% |
| 12.3 | 99% | 93-109% |
| 14.7 | 98% | 93-103% |
| 16.7 | 101% | 98-104% |
| 13.9 | 103% | 99-108% |
| 18.3 | 102% | 99-106% |

# Dilution recovery

Testing was performed to validate the manual dilution protocol (1:1 dilution on samples with results $>30.0\mathrm{ng / mL}$ ) recommended by the manufacturer in the package insert. Four native serum samples, with tacrolimus concentrations $>30\mathrm{ng / mL}$ on the Dimension® TAC assay, were used for this study. The expected values for these samples were assigned by LC-MS and ranged from 38.8 to $51.4\mathrm{ng / mL}$ . Two preparations of a 1:1 dilution of each sample were prepared using TAC Calibrator Level 1 as the diluent. Each aliquot of each sample tested in duplicate using the Dimension TAC method. The $\%$ recovery values after dilution are summarized below.

Dimension TAC - Dilution Recovery

| Sample # | Expected Value | Observed Value Corrected for Dilution | | Grand Mean ng/mL | % Recovery |
| --- | --- | --- | --- | --- | --- |
| | ng/mL | ng/mL | | | |
| 1 | 42.3 | 44.8 | 43.5 | 45.3 | 107.1 |
| 1 | 42.3 | 46.6 | 46.2 | | |
| | | | | | |
| 2 | 38.8 | 41.8 | 41.4 | 41.7 | 107.5 |
| 2 | 38.8 | 42.3 | 41.3 | | |

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| | | | | | |
| --- | --- | --- | --- | --- | --- |
| 3 | 48.2 | 49.0 | 47.7 | 49.4 | 102.4 |
| 3 | 48.2 | 50.3 | 50.5 | | |
| | | | | | |
| 4 | 51.4 | 57.2 | 54.0 | 56.4 | 109.8 |
| 4 | 51.4 | 56.8 | 57.7 | | |
| | | | | Average | 106.7 |

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

## Traceability and expected values

Siemens Tacrolimus (TAC) Calibrators are traceable to an internal reference standard gravimetrically prepared and confirmed via HPLC. Calibrators' values must be within $\pm 1\%$ of the reference calibrator value.

## Calibrator Stability

Real-time testing was performed. Protocols and acceptance criteria were reviewed and deemed acceptable. The shelf life for the Dimension TAC Calibrator is 12 months, at a storage temperature range of -15 to $-25^{\circ}\mathrm{C}$. Once thawed, assigned values are stable for 30 days when recapped immediately after use and stored at $2-8^{\circ}\mathrm{C}$.

## Sample Stability

The sponsor presented a study that supports the claim that whole blood samples collected in EDTA may be stored at $2 - 8^{\circ}\mathrm{C}$ or at ambient room temperature $(23.6^{\circ}\mathrm{C}$ to $24^{\circ}\mathrm{C})$ for up to 8 days before testing. A freeze-thaw study was also conducted to validate that EDTA whole blood samples could be stored frozen $(-20^{\circ}\mathrm{C})$ and thawed prior to analysis without affecting test results.

d. Detection limit:

Analytical sensitivities were determined following EP17-A2. LoB and LoD were determined using 5 patient samples free of tacrolimus, and 5 patient samples with low tacrolimus levels ranging from 0.2 to $1.7\mathrm{ng / mL}$. For limit of quantitation (LoQ), patient samples spiked with tacrolimus at 0.80, 0.85, 0.90, 0.95 and $1.00\mathrm{ng / mL}$ were tested. All samples were measured in replicates of 4 using two reagent lots over a period of 3 days. LoQ is defined as the lowest analyte concentration where the $\% \mathrm{CV}$ at the upper $95\%$ confidence limits is $\leq 20\%$.

The results are summarized in the below table.

| | LoB (ng/mL) | LoD (ng/mL) | LoQ (ng/mL) |
| --- | --- | --- | --- |
| Lot 1 | 0.5 | 0.7 | 0.9 |
| Lot 2 | 0.2 | 0.3 | 0.7 |
| Claimed | 0.5 | 0.7 | 1.0 |

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# e. Analytical specificity:

Interference testing was performed following EP-7A2. The compounds tested included endogenous compounds, drugs that are commonly co-administered with tacrolimus, as well as common over-the-counter drugs and the anticoagulant EDTA. The samples used for this study were prepared from whole blood to which purified tacrolimus drug was added to achieve target concentrations of $5\mathrm{ng/mL}$ and $20\mathrm{ng/mL}$ . Comparison between the test and control was done using the mean of five (5) replicates for each sample. The $\%$ difference between the spiked sample and the control sample with no substance was calculated. The sponsor defines no significant interference as bias within $\pm 10\%$ . For compounds that showed $>10\%$ bias, a dose response study was performed to determine the highest concentration at which no interference is observed. No interference was observed with the exogenous compounds tested and a complete list of the compounds and results are tabulated in the package insert. The endogenous substances tested and the maximum allowed concentration with no interference are summarized in the below table.

| Compound | Test Conc | %Recovery@ 5ng/mL TAC | % Recovery @ 20ng/mL TAC |
| --- | --- | --- | --- |
| Albumin | 6 g/dL | 101 | 100 |
| Albumin | 12 g/dL | 96 | 92 |
| Cholesterol Conjugated | 500 mg/dL | 91 | 99 |
| Bilirubin Unconjugated | 60 mg/dL | 99 | 96 |
| Bilirubin | 60 mg/dL | 96 | 95 |
| Creatinine | 30 mg/dL | 103 | 103 |
| IgG | 6 g/dL | 103 | 99 |
| IgG | 12 g/dL | 95 | 99 |
| Lipemia (Intralipid) | 1000 mg/dL | 92 | 94 |
| Rheumatoid Factor | 500 IU/mL | 98 | 98 |
| Total Protein | 3-4 g/L | 109 | 106 |
| Total Protein | 12 g/L | 95 | 98 |
| Triglycerides | 1000 mg/dL | 91 | 90 |
| Urea | 500 mg/dL | 100 | 97 |
| Uric Acid | 20 mg/dL | 101 | 96 |
| Hematocrit | 23.3 % | 104 | 99 |
| Hematocrit | 49.8 % | 102 | 100 |
| HAMA | Positive Sample 1 | 104 | 109 |
| HAMA | Positive Sample 2 | 105 | 105 |

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# Cross-reactivity:

Cross-reactivity was performed following EP-7A2. The samples used for this study were prepared from whole blood with or without the metabolite. Each sample was tested in replicate of 5 and the mean was used to calculate cross-reactivity using the below formula:

$\%$ Cross-reactivity $= 100\mathrm{x}$ (Test-Control)/ Concentration of Compound

The results are summarized in the table below.

Cross-reactivity of Tacrolimus Metabolites

| Metabolite | Concentration tested (ng/mL) | Concentration Detected (ng/mL)) | %Cross Reactivity |
| --- | --- | --- | --- |
| Major Metabolite | | | |
| M I (13-O-desmethyl-tacrolimus) | 40 | 0.2 | 1 |
| Minor Metabolites | | | |
| M II (31-O-desmethyl-tacrolimus) | 40 | 7.3 | 18 |
| M III (15-O-desmethyl-tacrolimus) | 40 | 6.0 | 15 |
| M IV (12-O-hydroxyl-tacrolimus) | 20 | 19.8 | 99 |
| Second Pass Metabolites | | | |
| M V (15,31-O-didesmethyl- | 40 | 0.3 | 1 |
| M VI (13,31-O-didesmethyl- | 40 | 0.2 | 1 |
| M VII (13,15-O-didesmethyl- | 40 | 17 | 43 |
| M VIII (unknown name) | 40 | 0 | 0 |
| Control | 0.0 | 0.5 | |

In the labeling, the sponsor has the following statement:

Patients undergoing retinal fluorescein angiography can retain amounts of fluorescein in the body for up to 36 to 48 hours post-treatment. In the cases of patients with renal insufficiency, including many diabetics, retention could be much longer. Such samples can produce falsely elevated values when tested with this assay, and should not be tested.

Triglycerides at $1500\mathrm{mg / dL}$ [16.9 mmol/L] decreases TAC results by $-18.7\%$ at a TAC concentration of $5\mathrm{ng / mL}$ [6.5 nmol/L] and decreases TAC results by $-12.1\%$ at $20\mathrm{ng / mL}$ [26.0 nmol/L].

Intralipid at $1500\mathrm{mg / dL}$ [16.9 mmol/L] decreases TAC results by $-13.6\%$ at a TAC concentration of $5\mathrm{ng / mL}$ [6.5 nmol/L] and decreases TAC results by $-18.6\%$ at a

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TAC concentration of 20 ng/mL [26.0 nmol/L].

Patient samples may contain heterophilic antibodies that could react in immunoassays to give falsely elevated or depressed results. Antibodies to β-galactosidase can be encountered in samples as a consequence of bacterial infection and may produce falsely elevated results which may not be consistent with clinical evaluation. The assay has been designed to minimize interference from antibodies to β-galactosidase. In very rare instances, immunoassays may produce falsely elevated or decreased results due to other patient-specific interferents. A number of these interferents are present in the plasma of affected patient samples and will be detected by the automatic rerun procedure.

Complete elimination of such interference from all patient specimens cannot be guaranteed. A test result that is inconsistent with the clinical picture and patient history should be interpreted with caution.

Confirmation of unexpected or atypical results by an alternative methodology is recommended prior to any adjustments in tacrolimus dosage. For patients with impaired liver function and patients receiving other drugs which may induce or inhibit microsomal enzyme activity, the routine use of the Dimension® Tacrolimus assay may be supported by HPLC data to assess possible changes in biotransformation and elimination.

f. Assay cut-off:

Not applicable – this is a quantitative assay.

2. Comparison studies:

a. Method comparison with predicate device:

Method comparison studies were performed at two external sites and an internal site using 3 lots of reagents (one lot/site). The collection protocol is the same across the 3 different sites, with approximately 100 patients enrolled at each site, and half from liver and half from kidney transplant patients. Each sample was tested in singlet using the candidate assay, and compared to the result of the predicate assay and the LC-MS method, respectively. The LC-MS method measures the parent drug of tacrolimus (MRM, mass transition of 821.6 m/z to 768.7 m/z). The exact number of patients tested at each site, and the Passing-Bablok regression analysis results are summarized in the below tables. The samples tested ranged from 1.2 – 25.6 ng/mL, which covered >80% of the assay range (1.0 – 30 ng/mL).

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Site 1/Lot 1

| Proposed TAC Assay versus | n | Slope | Intercept | Mean Bias | Std Dev. | R² |
| --- | --- | --- | --- | --- | --- | --- |
| LCMS | | | | | | |
| Total | 102 | 1.00 | -0.30 | -0.22 | 1.01 | 0.977 |
| Kidney only | 50 | 1.05 | -0.58 | 0.01 | 0.98 | 0.985 |
| Liver only | 52 | 0.90 | 0.14 | -0.44 | 0.99 | 0.947 |
| Abbott ARCHITECT | | | | | | |
| Total | 102 | 1.00 | -0.40 | -0.37 | 0.82 | 0.984 |
| Kidney only | 50 | 1.02 | -0.55 | -0.32 | 1.00 | 0.984 |
| Liver only | 52 | 1.00 | -0.40 | -0.43 | 0.61 | 0.975 |

Site 2/Lot 2

| Proposed TAC Assay versus | n | Slope | Intercept | Mean Bias | Std Dev. | R² |
| --- | --- | --- | --- | --- | --- | --- |
| LCMS | | | | | | |
| Total | 99 | 1.08 | -0.31 | 0.19 | 0.67 | 0.986 |
| Kidney only | 49 | 1.08 | -0.25 | 0.24 | 0.79 | 0.981 |
| Liver only | 50 | 1.07 | -0.36 | 0.14 | 0.53 | 0.990 |
| Abbott ARCHITECT | | | | | | |
| Total | 96 | 1.11 | -0.93 | -0.22 | 0.69 | 0.984 |
| Kidney only | 48 | 1.08 | -0.82 | -0.13 | 0.84 | 0.978 |
| Liver only | 48 | 1.11 | -0.95 | -0.32 | 0.50 | 0.993 |

Site3/lot3

| Proposed TAC Assay versus | n | Slope | Intercept | Mean Bias | Std Dev. | R² |
| --- | --- | --- | --- | --- | --- | --- |
| LCMS | | | | | | |
| Total | 114 | 1.05 | -0.41 | -0.33 | 1.32 | 0.945 |
| Kidney only | 59 | 1.13 | -1.34 | -0.68 | 1.53 | 0.922 |
| Liver only | 55 | 1.09 | -0.33 | 0.05 | 0.91 | 0.974 |
| Abbott ARCHITECT | | | | | | |
| Total | 110 | 0.90 | -0.05 | -0.85 | 0.90 | 0.983 |
| Kidney only | 56 | 0.95 | -0.44 | -0.86 | 0.77 | 0.982 |
| Liver only | 54 | 0.85 | 0.21 | -0.84 | 1.02 | 0.988 |

b. Matrix comparison:

Not applicable. The assay is intended for use with EDTA whole blood only.

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

4. Clinical cut-off:
Not applicable; this is a quantitative assay.

5. Expected values/Reference range:
The following is stated in the package insert:
No firm therapeutic range exists for tacrolimus in whole blood. The complexity of the clinical state, individual differences in sensitivity to immunosuppressive and nephrotoxic effects of tacrolimus, co-administration of other immunosuppressants, type of transplant, time post-transplant, and a number of other factors will cause different requirements for optimal blood levels of tacrolimus. Individual tacrolimus values cannot be used as the sole indicator for making changes in the treatment regimen. Each patient should be thoroughly evaluated clinically before treatment adjustments are made. Each assay user must establish therapeutic ranges based on clinical experience. Therapeutic ranges vary according to the commercial test method used, and therefore should be established for each commercial test. Values obtained with different assay methods cannot be used interchangeably due to differences in assay methods and cross-reactivity with metabolites, nor should correction factors be applied. Therefore, consistent use of one assay for individual patients is recommended.

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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