(105 days)
The ARK™ Methotrexate Assay is a homogeneous enzyme immunoassay intended for the quantitative determination of Methotrexate in human serum or automated clinical chemistry analyzers. The measurements obtained are used in monitoring levels of methotrexate to help ensure appropriate therapy.
The ARK™ Methotrexate Calibrator is intended for use in calibration of the ARK Methotrexate Assay.
The ARKTM Methotrexate Control is intended for use in quality control of the ARK Methotrexate Assay.
Specimens from patients who have received glucarpidase (carboxypeptidase G2) as a high dose methotrexate rescue therapy should not be tested with the ARK Methotrexate Assay.
The ARK Methotrexate Assay is a homogeneous immunoassay based on competition between drug in the specimen and Methotrexate labeled with the enzyme glucose-6-phosphate dehydrogenase (G6PDH) for binding to the antibody reagent. As the latter binds antibody, enzyme activity decreases. In the presence of drug from the specimen, enzyme activity increases and is directly proportional to the drug concentration. Active enzyme converts the coenzyme nicotinamide adenine dinucleotide (NAD) to NADH that is measured spectrophotometrically as a rate of change in absorbance. Endogenous serum G6PDH does not interfere with the results because the coenyzme NAD functions only with the bacterial enzyme used in the assay.
The ARK Methotrexate Assay consists of reagents R1 anti-Methotrexate polyclonal antibody with substrate and R2 Methotrexate labeled with bacterial G6PDH enzyme. The ARK Methotrexate Calibrator consists of a six-level set to calibrate the assay, and the ARK Methotrexate Control consists of a six-level set used for quality control of the assay (tri-level calibration range set and tri-level high range set). The ARK Methotrexate Dilution Buffer is equivalent to zero calibrator (Calibrator A).
Here's a breakdown of the acceptance criteria and the studies that prove the device meets them, based on the provided text:
Acceptance Criteria and Reported Device Performance
| Acceptance Criteria Category | Specific Acceptance Criteria | Reported Device Performance |
|---|---|---|
| Limit of Quantitation (LoQ) | LoB < Result < LoQ: report "analyte detected; concentration < LoQ" Result ≥ LoQ: report the result as measured | LoB: 0.01 µmol/L LoD: 0.02 µmol/L LoQ: 0.04 µmol/L (LoQ-2 SD > LoD met) |
| Accuracy (Analytical Recovery) | Not explicitly stated as a numerical criterion in the "Acceptance Criteria" section for each data point, but typically implied to be close to 100% recovery. | Mean percentage recovery: 102.1% (Individual recoveries ranged from 98.3% to 111.1%) |
| Linearity | Percent difference was ±10% between the predicted 1st and 2nd order regressed values for concentrations >0.10 µmol/L or ±0.01 µmol/L at concentrations ≤ 0.10 µmol/L. | All observed differences for concentrations >0.10 µmol/L were within ±10% (-2.3% to 4.8%).All observed differences for concentrations ≤ 0.10 µmol/L were within ±0.01 µmol/L (-0.010 µmol/L to -0.004 µmol/L). The highest theoretical concentration tested was 1.30 µmol/L. Regression of assayed methotrexate concentrations was linear throughout the range of 2 to 1200 µmol/L when proportionally diluted. |
| Assay Range | Not explicitly stated as an acceptance criterion, but the functional range. | Measurement range: 0.04 - 1.20 µmol/L |
| Method Comparison | Not explicitly stated as a numerical acceptance criterion (e.g., minimum correlation coefficient or confidence intervals for slope/intercept), but comparison to a predicate device is expected. | Range 0.04 to 1.19 µM (102 samples): Slope: 1.00 (95% CI: 1.00 to 1.02) y-intercept: 0.01 (95% CI: 0.00 to 0.01) Correlation Coefficient (r²): 0.978 (95% CI: 0.968 to 0.985)Range 0.04 to 1440 µM (147 samples, including diluted): Slope: 0.99 (95% CI: 0.96 to 1.00) y-intercept: 0.01 (95% CI: 0.01 to 0.01) Correlation Coefficient (r²): 0.998 (95% CI: 0.997 to 0.998) |
| Precision | <10% total CV at >0.10 µmol/L SD ≤0.01 at ≤0.10 µmol/L | All control and patient pool samples met the criteria: - ARK Methotrexate Control (MID, HIGH, 5, 50, 500 µmol/L): Total CVs ranged from 3.8% to 7.0%. - ARK Methotrexate Control (LOW, 0.06 µmol/L): Total SD was 0.007, which is ≤0.01. - Patient Pool (MID, HIGH, 5, 50, 500 µmol/L): Total CVs ranged from 5.3% to 7.2%. - Patient Pool (LOW, 0.07 µmol/L): Total SD was 0.008, which is ≤0.01. |
| Interfering Substances | Not substantially affected by tested endogenous substances. | Measurement of methotrexate was not substantially affected by clinically high concentrations of Albumin, Bilirubin (conjugated & unconjugated), Cholesterol, Gamma-Globulin, Hemoglobin, Intralipid®, Rheumatoid Factor, Triglycerides, and Uric Acid. |
| Specificity - Crossreactivity | < 0.07% crossreactivity with 7-Hydroxymethotrexate. | 7-Hydroxymethotrexate: ≤ 0.07% crossreactivity. DAMPA: 64.3% to 100% crossreactivity (significant). Triamterene: Crossreactivity ranged from 1.85% to 3.32%. Trimethoprim: Crossreactivity ranged from 0.12% to 0.54%. Folate analogs and other compounds (e.g., Adriamycin, Cyclophosphamide): ≤ 0.01% crossreactivity at ≥ 1000 µmol/L. |
| Anticoagulants | No significant difference in recovery between serum and plasma. | No significant difference found in methotrexate recovery between serum and plasma samples. |
| Sample Stability | Acceptable stability under various storage conditions. | Stable frozen (at least 15 months), 48 hours at room temperature, refrigerated (at least 21 days), and after three (3) successive freeze/thaw cycles. |
| On-Board Stability | Acceptable stability of calibration curve and reagents on the analyzer. | Calibration curve effective up to at least 19 days. Reagents effective for up to at least 25 days in analyzer-specific containers. In-use stability of calibrator and controls also demonstrated. |
Study Details
2. Sample sizes used for the test set and the data provenance (e.g. country of origin of the data, retrospective or prospective):
- Limit of Quantitation (LoQ):
- LoB, LoD: N = 60
- LoQ: N = 40
- Data provenance: Not specified, but generally analytical studies like this are conducted with prepared samples in a laboratory setting (prospective).
- Accuracy: Concentrated methotrexate drug added into human serum negative for methotrexate. Six replicates of each sample were assayed.
- Sample size: 5 target concentrations, each with 6 replicates (30 assays).
- Data provenance: Not specified, but likely prospective, prepared samples in a lab.
- Linearity: Dilutions of a 1.30 µmol/L serum sample and proportional dilutions of samples between 2 and 1200 µmol/L in pooled human serum.
- Sample size: 13 different concentrations were tested for the initial linearity study. The second linearity study for higher concentrations (2-1200 µmol/L) stated "samples containing methotrexate... were prepared proportionally," implying multiple samples across this range.
- Data provenance: Not specified, but likely prospective, prepared samples in a lab.
- Method Comparison:
- Sample size: 102 specimens within the measurement range (0.04 to 1.19 µM) and 147 specimens including those above the measurement range requiring dilution (total range 0.04 to 1440 µM).
- Data provenance: Not specified, but these are likely clinical samples (human serum/plasma), which could be retrospective or prospective. The document does not specify country of origin.
- Precision:
- Sample size: Each of the 6 control levels and 6 patient pool levels were assayed in quadruplicate, twice a day for 20 days. This means 4 * 2 * 20 = 160 measurements per level.
- Data provenance: Not specified, but likely prospective, prepared controls and pooled patient samples in a lab.
- Interfering Substances: Multiple substances tested, each with samples at ~0.05 and ~0.50 µmol/L methotrexate.
- Sample size: Each interfering substance was tested at two methotrexate levels, likely with duplicates or triplicates, plus control samples. The specific number of individual assays is not given but implies a significant number of tests.
- Data provenance: Not specified, but likely prospective, prepared samples in a lab setting.
- Specificity (Crossreactivity):
- Sample size: Two concentrations of methotrexate (0.05 and 0.50 µmol/L) were tested with triamterene and trimethoprim. Various other compounds and folate analogs were tested at high concentrations (e.g., ≥ 1000 µmol/L), presumably just once for cross-reactivity.
- Data provenance: Not specified, but likely prospective, prepared samples in a lab setting.
- Anticoagulants:
- Sample size: "Studies were conducted," implying multiple samples, but no specific number is given.
- Data provenance: Not specified, but likely prospective, prepared samples in a lab setting.
- Sample Stability:
- Sample size: Not specified, but involved human specimens.
- Data provenance: Not specified, but likely prospective.
- On-Board Stability:
- Sample size: Not specified, but utilized a calibration curve and reagents over time.
- Data provenance: Not specified, but likely prospective, lab-based testing.
3. Number of experts used to establish the ground truth for the test set and the qualifications of those experts (e.g. radiologist with 10 years of experience):
This device is an in vitro diagnostic assay for quantitative determination of methotrexate. The "ground truth" for such assays is typically established by:
- Reference materials: Certified reference standards for methotrexate concentration (used in Accuracy, LoQ, Linearity, Crossreactivity).
- Predicate device comparison: The "gold standard" or accepted method (Fluorescence Polarization Immunoassay - FPIA in this case, specifically the Abbott TDx®/TDxFLx® Methotrexate II assay) for method comparison.
Therefore, the concept of "experts" establishing ground truth as it applies to image interpretation (like radiologists) or pathological diagnosis is not directly relevant here. The ground truth is analytical and based on established methodology and certified materials.
4. Adjudication method (e.g., 2+1, 3+1, none) for the test set:
Not applicable. Adjudication methods like 2+1 or 3+1 are typically used in clinical studies where subjective human interpretation (e.g., reading medical images) is involved and discrepancies between readers need to be resolved to establish a consensus ground truth. For in vitro diagnostic device performance studies, the results are quantitative and compared against analytical or predicate methods, not subjective expert consensus.
5. If a multi-reader multi-case (MRMC) comparative effectiveness study was done, If so, what was the effect size of how much human readers improve with AI vs without AI assistance:
Not applicable. This device is an in vitro diagnostic assay, not an AI-powered image analysis tool or a device requiring human "readers" in the context of an MRMC study. Its performance is evaluated analytically, not by assessing human performance improvement with or without AI.
6. If a standalone (i.e. algorithm only without human-in-the-loop performance) was done:
Yes, all the performance studies described (analytical recovery, linearity, method comparison, precision, interference, specificity, stability) represent the standalone performance of the ARK Methotrexate Assay. There is no human-in-the-loop aspect described in these tests; the assay directly provides quantitative results.
7. The type of ground truth used (expert consensus, pathology, outcomes data, etc):
The ground truth used for this in vitro diagnostic assay consists of:
- Reference Standards: For accuracy, LoQ, linearity, and specificity, the ground truth was based on precisely known concentrations of methotrexate prepared using certified stock concentrates.
- Predicate Device (Monoclonal FPIA): For method comparison, the ground truth was the results obtained from the legally marketed predicate device (Abbott TDx®/TDxFLx® Methotrexate II), which is an established method for methotrexate measurement.
- Pre-defined Parameters/Conditions: For interference, specificity, and stability studies, the ground truth was the expectation of what the device should measure under specific well-defined conditions (e.g., no cross-reactivity with certain compounds, stability over a given period).
8. The sample size for the training set:
Not applicable. This document describes the validation of an immunoassay kit, not a machine learning or AI algorithm that requires a "training set." Immunoassays are based on biochemical reactions with antibodies, not pattern recognition learned from data.
9. How the ground truth for the training set was established:
Not applicable, as there is no "training set" in the context of this immunoassay device.
{0}------------------------------------------------
OCT 1 8 2011
510(k) SUMMARY
This summary of 510(k) safety and effectiveness information is being submitted in accordance with the requirements of SMDA 1990 and 21 CFR 807.92.
The assigned 510(k) number is K111904.
| 807.92 (a)(1): Name: | ARK Diagnostics, Inc. |
|---|---|
| Address: | 1190 Bordeaux DriveSunnyvale, CA 94089 |
| Owner Operator Number: | 10027663 |
| Establishment Registration: | 3005755244 |
| Phone: | (408) 747-0700 |
| FAX: | (408) 747-0783 |
| Contact: | Kenneth C. Kasper, PhD – (408) 747-0708Executive Director of Quality and Regulatory Affairs |
Date prepared: September 7, 2011
807.92 (a)(2): Device name- trade name and common name, and classification
| Trade name: | ARKTM Methotrexate AssayARKTM Methotrexate CalibratorARKTM Methotrexate Control |
|---|---|
| Common Name: | Homogeneous Enzyme Immunoassay |
| Classification: | 21 CFR 862 Clinical Chemistry Test System - ToxicologyTest Code LAO; Enzyme Immunoassay, MethotrexatePre-Amendment Device, Unclassified(21 CFR 862.3200 DLJ, 21 CFR 862.3280 LAS) |
807.92 (a)(3): Identification of the legally marketed predicate device
Abbott TDx®/TDxFLx® METHOTREXATE II (K932615)
... «
{1}------------------------------------------------
807.92 (a)(4): Device Description
The ARK Methotrexate Assay is a homogeneous immunoassay based on competition between drug in the specimen and Methotrexate labeled with the enzyme glucose-6-phosphate dehydrogenase (G6PDH) for binding to the antibody reagent. As the latter binds antibody, enzyme activity decreases. In the presence of drug from the specimen, enzyme activity increases and is directly proportional to the drug concentration. Active enzyme converts the coenzyme nicotinamide adenine dinucleotide (NAD) to NADH that is measured spectrophotometrically as a rate of change in absorbance. Endogenous serum G6PDH does not interfere with the results because the coenyzme NAD functions only with the bacterial enzyme used in the assay.
The ARK Methotrexate Assay consists of reagents R1 anti-Methotrexate polyclonal antibody with substrate and R2 Methotrexate labeled with bacterial G6PDH enzyme. The ARK Methotrexate Calibrator consists of a six-level set to calibrate the assay, and the ARK Methotrexate Control consists of a six-level set used for quality control of the assay (tri-level calibration range set and tri-level high range set). The ARK Methotrexate Dilution Buffer is equivalent to zero calibrator (Calibrator A).
807.92 (a)(5): Intended Use / Indications for Use
The ARK Methotrexate Assay is a homogeneous enzyme immunoassay intended for the quantitative determination of methotrexate in human serum or plasma on automated clinical chemistry analyzers. The measurements obtained are used in monitoring levels of methotrexate to help ensure appropriate therapy.
The ARK Methotrexate Calibrator is intended for the ARK Methotrexate Assay.
The ARK Methotrexate Control is intended for the quality control of the ARK Methotrexate Assay.
Specimens from patients who have received glucarpidase (carboxypentidase G2) as a high dose methotrexate rescue therapy should not be tested with the ARK Methotrexate Assay.
{2}------------------------------------------------
807.92 (a)(6): Technological Similarities and Differences to the Predicate
SUBSTANTIAL EQUIVALENCE COMPARATIVE CHART
| Characteristic | Device | Predicate |
|---|---|---|
| ARK™ Methotrexate Assay | Abbott TDx®/TDxFLx® Methotrexate II (K932615) | |
| Intended Use | The ARK™ Methotrexate Assay is intended for the quantitative determination of methotrexate in human serum or plasma on automated clinical chemistry analyzers. | The TDx®/TDxFLx® Methotrexate II assay is a reagent system for the quantitative measurement of methotrexate, an antineoplastic drug, in serum or plasma. |
| Indications for Use | The measurements obtained are used in monitoring levels of methotrexate to help ensure appropriate therapy. | The measurements obtained are used in monitoring levels of methotrexate to ensure appropriate therapy. |
| Sample | Serum or plasma | Serum or plasma |
| Methodology | Homogenous enzyme immunoassay (EIA) | Fluorescence polarization immunoassay (FPIA) |
| Reagent Components | Two (2) reagent system:Anti-Methotrexate Antibody/Substrate Reagent (RI) containing rabbit polyclonal antibodies to Methotrexate, glucose-6-phosphate, nicotinamide adenine dinucleotide, bovine serum albumin, preservatives, and stabilizersEnzyme Reagent (R2) containing Methotrexate labeled with bacterial G6PDH, buffer, bovine serum albumin, preservatives, and stabilizers | Reagent Pack:W = Wash solution, solvent, sodium azideS = Methotrexate Antibody (mouse monoclonal), buffer, protein and sodium azideT = Methotrexate Fluorescein Tracer, buffer, protein, surfactant and sodium azideP = Pretreatment Solution, protein, surfactant and sodium azide |
| Platform required | Automated clinical chemistry analyzer | TDx clinical chemistry analyzer |
| Accessory reagents | Calibrators (six levels) and controls (six levels) in a synthetic matrix; Dilution Buffer | Calibrators (six levels) and controls (six levels) in human serum; Dilution Buffer |
| Testing environment | Routine clinical laboratory | Routine clinical laboratory |
| Reagent condition and storage | Liquid, 2-8° C | Liquid, 2-8° C |
Comparison between the ARK™ Methotrexate Assay and TDx®/TDxFLx® Methotrexate II Assay
{3}------------------------------------------------
807.92 (b)(1) and 807.92 (b)(2): Brief Description of Nonclinical and Clinical Data
Limit of Quantitation (LOQ)
The following characteristics were determined according to CLSI EP17-A for the ARK Methotrexate Assay. Analyzer-specific performance may vary.
| Criterion | MTX Concentration ( $ $ mol/L) |
|---|---|
| Limit of Blank (LoB); N = 60 | 0.01 |
| $ $ B + 1.645 SD, where SD = 0.005 | |
| Limit of Detection (LoD); N = 60 | 0.02 |
| LoB + 1.652 SD, where SD = 0.005 | |
| Limit of Quantitation (LoQ); N = 40 | 0.04 |
| LoQ-2 SD > LoD |
Each laboratory is responsible for determining reporting criteria for methotrexate concentrations. The following suggestion from CLSI EP17-A may be appropriate:
| Result ≤ LoB | report "not detected; concentration < LoD" |
|---|---|
| LoB < Result < LoQ | report "analyte detected; concentration < LoQ" |
| Result ≥ LoQ | report the result as measured |
ARK Diagnostics, Inc. - 510(k) Summary ARK Methotrexate Assay
{4}------------------------------------------------
Accuracv
Accuracy (analytical recovery) was performed by adding concentrated methotrexate drug into human serum negative for methotrexate. A certified stock concentrate of highly pure methotrexate was added volumetrically to human serum negative for methotrexate, representing drug concentrations across the assay calibration range. Six replicates of each sample were assayed on an automated clinical chemistry analyzer. The results were averaged and compared to the target concentration and percent recovery calculated. Results are shown below.
% Recovery = 100 X Mean recovered concentration Target concentration
| TheoreticalConcentration(umol/L) | Mean RecoveredConcentration(umol/L) | PercentageRecovery |
|---|---|---|
| 0.06 | 0.07 | 111.1 |
| 0.10 | 0.10 | 100.0 |
| 0.30 | 0.30 | 98.3 |
| 0.60 | 0.61 | 102.2 |
| 1.00 | 0.99 | 98.8 |
Mean percentage recovery: 102.1
{5}------------------------------------------------
Linearity
Linearity studies were performed as suggested in CLSI/NCCLS Protocol EP6-A. A 1.30 umol/L serum sample was prepared and dilutions were made proportionally with human serum negative for methotrexate. Linearity at specific dilutions was considered acceptable if the percent difference was ±10% between the predicted 15 and 2nd order regressed values for concentrations >0:10 umol/L or ±0.01 umol/L at concentrations ≤ 0.10 µmol/L. Results are shown below.
| Theoretical(µmol/L) | ObservedResults(µmol/L) | 1st OrderPredictedResults | 2nd OrderPredictedResults | Difference(µmol/L or %) |
|---|---|---|---|---|
| 0.00 | 0.00 | 0.009 | -0.003 | na |
| 0.02 | 0.02 | 0.026 | 0.016 | -0.010 µmol/L |
| 0.04 | 0.04 | 0.042 | 0.034 | -0.008 µmol/L |
| 0.05 | 0.06 | 0.059 | 0.053 | -0.006 µmol/L |
| 0.07 | 0.08 | 0.076 | 0.072 | -0.004 µmol/L |
| 0.11 | 0.11 | 0.110 | 0.109 | -0.7 % |
| 0.18 | 0.17 | 0.178 | 0.183 | 3.1 % |
| 0.36 | 0.34 | 0.347 | 0.364 | 4.8 % |
| 0.65 | 0.63 | 0.618 | 0.639 | 3.4 % |
| 0.72 | 0.72 | 0.686 | 0.705 | 2.9 % |
| 0.86 | 0.84 | 0.821 | 0.835 | 1.7 % |
| 1.01 | 0.99 | 0.957 | 0.960 | 0.4 % |
| 1.15 | 1.06 | 1.092 | 1.082 | -1.0 % |
| 1.30* | 1.19 | 1.228 | 1.199 | -2.3 % |
*Concentration exceeds the claimed calibration range.
Samples containing methotrexate between 2 and 1200 umol/L were prepared proportionally in pooled human serum and then diluted into the calibration range with ARK Methotrexate Dilution Buffer. Regression of assayed methotrexate concentrations was linear throughout the range.
{6}------------------------------------------------
Assay Range
The measurement range of the ARK Methotrexate Assay is 0.04 - 1.20 umol/L. Specimens containing methotrexate in higher concentrations are assayed by dilution of the specimen. Report assayed values exceeding the LoD according to the information provided for LoQ. Multiply the assayed result by the dilution factor for specimens containing methotrexate above the measurement range.
Method Comparison
Correlation studies were performed using CLSI/NCCLS Protocol EP9-A2. Results from the ARK Methotrexate Assay were compared with results from Fluorescence Polarization Immunoassay method (monoclonal FPIA).
Methotrexate concentrations by FPIA ranged 0.04 to 1440 umol/L (uM). ARK Methotrexate values ranged 0.04 to 1500 umol/L. Results of the Passing-Bablok regression analysis for the study are shown below (with 95% confidence limits) for 102 specimens within the measurement range as well as for all 147 specimens including those above the measurement range requiring dilution.
| Parameter | Range 0.04 to 1.19 μM | Range 0.04 to 1440 μM | |||
|---|---|---|---|---|---|
| Slope | 1.00 | (1.00 to 1.02) | 0.99 | (0.96 to 1.00) | |
| y-intercept | 0.01 | (0.00 to 0.01) | 0.01 | (0.01 to 0.01) | |
| Correlation Coefficient (r2) | 0.978 | (0.968 to 0.985) | 0.998 | (0.997 to 0.998) | |
| Number of Samples | 102 | na | 147 | na |
{7}------------------------------------------------
Precision
Precision was determined as described in CLSI/NCCLS Protocol EP5-A2. The six-level ARK Methotrexate Control and pooled human specimens containing methotrexate were used in the study. Each level was assayed in quadruplicate twice a day for 20 days. Each of the runs per day was separated by at least two hours. The within-run, between-day, total SD, and percent CVs were calculated. Results are shown below. Acceptance criteria: <10% total CV at >0.10 µmol/L, SD ≤0.01 at ≤0.10 µmol/L.
| Sample | N | Mean(µmol/L) | Within Run | Between Day | Total | |||
|---|---|---|---|---|---|---|---|---|
| SD | %CV | SD | %CV | SD | %CV | |||
| ARK Methotrexate Control | ||||||||
| LOW | 160 | 0.06 | 0.005 | 8.1 | 0.005 | 7.1 | 0.007 | 10.6 |
| MID | 160 | 0.37 | 0.011 | 3.1 | 0.008 | 2.2 | 0.014 | 3.8 |
| HIGH | 160 | 0.76 | 0.039 | 5.1 | 0.029 | 3.8 | 0.048 | 6.4 |
| 5 | 160 | 4.8 | 0.13 | 2.8 | 0.013 | 2.8 | 0.19 | 4.1 |
| 50 | 160 | 48 | 1.40 | 2.9 | 2.13 | 4.4 | 2.71 | 5.6 |
| 500 | 160 | 470 | 15.63 | 3.3 | 27.64 | 5.8 | 33.35 | 7.0 |
| Patient Pool | ||||||||
| LOW | 160 | 0.07 | 0.006 | 9.1 | 0.005 | 7.5 | 0.008 | 11.7 |
| MID | 160 | 0.41 | 0.013 | 3.3 | 0.026 | 6.4 | 0.030 | 7.2 |
| HIGH | 160 | 0.82 | 0.037 | 4.5 | 0.042 | 5.1 | 0.057 | 6.9 |
| 5 | 160 | 4.6 | 0.14 | 3.1 | 0.18 | 4.0 | 0.24 | 5.3 |
| 50 | 160 | 45 | 1.31 | 2.9 | 2.62 | 5.9 | 2.92 | 6.5 |
| 500 | 160 | 460 | 11.55 | 2.5 | 27.21 | 5.9 | 29.63 | 6.4 |
{8}------------------------------------------------
Interfering Substances
Interference studies were conducted using CLSI/NCCLS Protocol EP7-A2 as a guideline. Clinically high concentrations of the following potentially interfering endogenous substances in serum with known levels of methotrexate (approximately 0.05 and 0.50 umol/L) were evaluated. Fach sample was assayed using the ARK Methotrexate Assay, along with a serum control of methotrexate. Measurement of methotrexate was not substantially affected at the levels of endogenous substances tested.
| Methotrexate(~ 0.05 µmol/L) | Methotrexate(~ 0.50 µmol/L) | ||||
|---|---|---|---|---|---|
| InterferingSubstance | InterferentConcentration | SerumControl | Test | SerumControl | Test(% Control) |
| Albumin | 12 g/dL | 0.05 | 0.06 | 0.48 | 0.45 ( 92.8) |
| Bilirubin - conjugated | 70 mg/dL | 0.05 | 0.06 | 0.48 | 0.51 (105.5) |
| Bilirubin - unconjugated | 70 mg/dL | 0.05 | 0.06 | 0.48 | 0.52 (106.9) |
| Cholesterol | 400 mg/dL | 0.05 | 0.06 | 0.47 | 0.49 (105.4) |
| Gamma-Globulin | 12 g/dL | 0.05 | 0.06 | 0.48 | 0.51 (105.5) |
| Hemoglobin | 1000 mg/dL | 0.04 | 0.05 | 0.49 | 0.45 ( 92.8) |
| Intralipid® | 500 mg/dL | 0.05 | 0.05 | 0.43 | 0.45 (105.1) |
| Rheumatoid Factor | 1100 IU/mL | 0.05 | 0.06 | 0.43 | 0.41 ( 96.1 ) |
| Triglycerides | 749 mg/dL | 0.04 | 0.04 | 0.49 | 0.45 ( 91.4) |
| Uric Acid | 30 mg/dL | 0.05 | 0.04 | 0.48 | 0.50 (102.8) |
Specificity - Drug Interference
Crossreactivity to 7-Hydroxymethotrexate, the major metabolite
The ARK Methotrexate Assay did not crossreact (≤ 0.07%) with the major metabolite 7-Hydroxymethotrexate.
Crossreactivity to the minor, inactive metabolite 2,4-diamino-N18-methylpteroic acid (DAMPA)
The ARK Methotrexate Assay crossreacts substantially with the minor metabolite DAMPA. Tests were performed in the absence of the parent drug methotrexate. Crossreactivity to DAMPA ranged 64.3 to 100%. The assay should not be used during possible compassionate therapy with glucarpidase (carboxypeptidase G2) that rapidly converts circulating methotrexate to DAMPA.
Drugs that crossreact
The ARK Methotrexate Assay crossreacts slightly with triamterene and trimethoprim, however these drugs may be contraindicated for methotrexate cancer treatement due to additional adverse effects if co-administered. The structures of these compounds closely match the pteridine ring moiety of methotrexate.
ARK Diagnostics, Inc. - 510(k) Summary ARK Methotrexate Assay
{9}------------------------------------------------
| Methotrexate Absent | Methotrexate Present0.05 µmol/L | Methotrexate Present0.50 µmol/L | |||||
|---|---|---|---|---|---|---|---|
| Compound | Tested(µmol/L) | MTX(µmol/L) | CrossReactivity(%) | MTX(µmol/L) | CrossReactivity(%) | MTX(µmol/L) | CrossReactivity(%) |
| Triamterene | 25 | 0.46 | 1.85 | 0.89 | 3.32 | 1.04 | 2.31 |
| Trimethoprim | 100 | 0.17 | 0.17 | 0.16 | 0.12 | 0.99 | 0.54 |
Crossreactivity to folate analogs and other compounds
The ARK Methotrexate Assay did not crossreact (≤ 0.01%) with folate analogs or other compounds at ≥ 1000 umol/L as tested.
| Compound | Tested(µmol/L) |
|---|---|
| Adriamycin | 1000 |
| Cyclophosphamide | 1500 |
| Cytosine | 1000 |
| Dihydrofolic Acid | 1000 |
| DL-6-Methyl-5,6,7,8-Tetrahydropterine | 1000 |
| Folic Acid | 1000 |
| Folinic Acid (leucovorin) | 1000 |
| 5-Fluorouracil | 3000 |
| 6-Mercaptopurine | 1000 |
| 5-Methyltetrahydrofolic acid | 1000 |
| Prednisolone | 1000 |
| Pyrimethamine | 1000 |
| Sulfamethoxazole | 1600 |
| Tetrahydrofolic Acid | 1000 |
| Vinblastine | 1000 |
| Vincristine | 1000 |
Anticoagulants
Studies were conducted to determine the performance characteristics of the assay for both serum and plasma samples containing methotrexate.
The results indicate that there is no significant difference between the recovery of methotrexate in serum or plasma.
{10}------------------------------------------------
Sample Stability
Human specimens were shown to be stable frozen (at least 15 months), forty-eight (48) hours at room temperature, refrigerated (at least 21 days) and after three (3) successive freeze/thaw cycles.
On-Board Stability
Calibration Curve Stability: A stored calibration was effective up to at least 19 days based on supporting data.
Reagent on-board stability: Reagents were effective when stored after transfer to analyzer specific reagent containers for up to at least 25 days based on supporting data. In-use stability of calibrator and controls was also demonstrated.
807.92 (b)(3): Conclusions from Nonclinical Testing
As summarized above, the ARK Methotrexate Assay System, including the ARK Methotrexate Calibrator, ARK Methotrexate Control and ARK Methotrexate Dilution Buffer, is substantially equivalent to the Abbott TDx®/TDxFLx® METHOTREXATE II Assay system. The ARK Methotrexate Assay system was shown to be safe and effective for its intended use based on performance studies.
{11}------------------------------------------------
Image /page/11/Picture/0 description: The image shows the logo of the Department of Health & Human Services (HHS) of the United States. The logo consists of a circular seal with the text "DEPARTMENT OF HEALTH & HUMAN SERVICES - USA" around the perimeter. Inside the circle is an abstract symbol resembling an eagle or bird in flight, which is the official emblem of the HHS.
Food and Drug Administration 10903 New Hampshire Avenue Silver Spring, MD 20993
ARK Diagnostics, Inc c/o Kenneth C. Kasper, PhD 1190 Bordeaux Dr. Sunnyvale, CA 94089
OCT 1 8 2011
Re: K111904
Trade/Device Name: ARK™ Methotrexate Assay, ARK™ Methotrexate Calibrator, ARK™ Methotrexate Control Regulatory Class: Unclassified, 510(k) required Product Code: LAO, DLJ, LAS Dated: September 7, 2011 Received: September 8, 2011
Dear Dr. Kasper:
We have reviewed your Section 510(k) premarket notification of intent to market the device referenced above and have determined the device is substantially equivalent (for the indications for use stated in the enclosure) to legally marketed predicate devices marketed in interstate commerce prior to May 28, 1976, the enactment date of the Medical Device Amendments, or to devices that have been reclassified in accordance with the provisions of the Federal Food, Drug, and Cosmetic Act (Act) that do not require approval of a premarket approval application (PMA). You may, therefore, market the device, subject to the general controls provisions of the Act. The general controls provisions of the Act include requirements for annual registration, listing of devices, good manufacturing practice, labeling, and prohibitions against misbranding and adulteration.
If your device is classified (see above) into class II (Special Controls), it may be subject to such additional controls. Existing major regulations affecting your device can be found in Title 21, Code of Federal Regulations (CFR), Parts 800 to 895. In addition, FDA may publish further announcements concerning your device in the Federal Register.
Please be advised that FDA's issuance of a substantial equivalence determination does not mean that FDA has made a determination that your device complies with other requirements of the Act or any Federal statutes and regulations administered by other Federal agencies. You must comply with all the Act's requirements, including, but not limited to: registration and listing (21 CFR Part 807); labeling (21 CFR Parts 801 and 809); medical device reporting (reporting of medical device-related adverse events) (21 CFR 803); and good manufacturing practice requirements as set forth in the quality systems (QS) regulation (21 CFR Part 820). This letter will allow you to begin marketing your device as described in your Section 510(k) premarket notification. The FDA finding of substantial equivalence of your device to a legally marketed predicate device results in a classification for your device and thus, permits your device to proceed to the market.
{12}------------------------------------------------
Page 2 -
If you desire specific advice for your device on our labeling regulation (21 CFR Part 801), please contact the Office of In Vitro Diagnostic Device Evaluation and Safety at (301) 796-5450. Also, please note the regulation entitled, "Misbranding by reference to premarket notification" (21 CFR Part 807.97). For questions regarding postmarket surveillance, please contact CDRH's Office of Surveillance and Biometric's (OSB's) Division of Postmarket Surveillance at (301) 796-5760. For questions regarding the reporting of adverse events under the MDR regulation (21 CFR Part 803), please go to http://www.fda.gov/MedicalDevices/Safety/ReportaProblem/default.htm for the CDRH's Office of Surveillance and Biometrics/Division of Postmarket Surveillance.
You may obtain other general information on your responsibilities under the Act from the Division of Small Manufacturers, International and Consumer Assistance at its toll-free number (800) 638-2041 or ( 301 ) 796-5680 or at its Internet address http://www.fda.gov/MedicalDevicesforYou/Industry/default.htm.
Sincerely yours,
jz
Courtney H. Lias, Ph.D. Director Division of Chemistry and Toxicology Office of In Vitro Diagnostic Device Evaluation and Safety Center for Devices and Radiological Health
Enclosure
{13}------------------------------------------------
Indication for Use
510(K) Number (if known): K111904
Device Name:
ARKTM Methotrexate Assay ARKTM Methotrexate Calibrator ARKTM Methotrexate Control
Indications for Use:
The ARK™ Methotrexate Assay is a homogeneous enzyme immunoassay intended for the quantitative determination of Methotrexate in human serum or automated clinical chemistry analyzers. The measurements obtained are used in monitoring levels of methotrexate to help ensure appropriate therapy.
The ARK™ Methotrexate Calibrator is intended for use in calibration of the ARK Methotrexate Assay.
The ARKTM Methotrexate Control is intended for use in quality control of the ARK Methotrexate Assay.
Specimens from patients who have received glucarpidase (carboxypeptidase G2) as a high dose methotrexate rescue therapy should not be tested with the ARK Methotrexate Assay.
Prescription Use ____X (21 CFR Part 801 Subpart D) Over the Counter Use (21 CFR Part 801 Subpart C)
(PLEASE DO NOT WRITE BELOW THIS LINE; CONTINUE ON ANOTHER PAGE IF NEEDED)
And/Or
Concurrence of CDRH, Office of In Vitro Diagnostic Device Evaluation and Safety (OIVD)
Ritte charles
Division Sign-Off Office of In Vitro Diagnostic Device Evaluation and Safety
111904 510(k)
ARK Methotrexate Assay - Indications/Intended Use ARK Diagnostics, Inc.
Page 1 of 1
N/A