4 Reagents
Reagents contain the following substances: Mouse monoclonal antibodies reactive to procainamide (52 µg/mL), glucose-6-phosphate (22 mM), nicotinamide adenine dinucleotide (18 mM), procainamide labeled with glucose-6-phosphate dehydrogenase (0.2 U/mL), Tris buffer, preservatives, and stabilizers. Procainamide Assay Precautions • For in vitro diagnostic use. • Contains nonsterile mouse monoclonal antibodies. September 2010 4K052.3D_B • Do not use the kit after the expiration date. • Turbid or yellow reagents may indicate contamination or degradation and must be discarded.
Preparation of Reagents The Emit® 2000 Procainamide Assay reagents are provided ready to use. No preparation is necessary.
Storage of Assay Components • Improper storage of reagents can affect assay performance. • When not in use, store reagents upright at 2–8°C and with screw caps tightly closed. Catalog Quantity/ Number Product Description Volume • Unopened reagents are stable until the expiration date printed on the label if stored upright at 2–8°C. OSR4K229 Emit® 2000 Procainamide Assay • Do not freeze reagents or expose them to temperatures above 32°C. OSR4K518 R1 (Antibody/Substrate Reagent 1) 2 x 23 mL OSR4K548 R2 (Enzyme Reagent 2) 2 x 13 mL 5 Specimen Collection and Preparation 4K109UL Emit® 2000 Procainamide Calibrators* 1 x 5 mL†, 5 x 2 mL • Each assay requires serum or plasma. Whole blood cannot be used. The anticoagulants heparin, citrate, oxalate, and EDTA have been tested and may be used with this assay. *Required for calibrating the Emit ® 2000 Procainamide Assay. Sold separately. Some sample dilution may occur when samples are collected in tubes containing citrate †Additional negative calibrator is provided. anticoagulant. The amount of dilution and the possible need to correct for it should be considered when interpreting assay results for these samples. Note: Reagents and calibrators are shipped ready to use in liquid form. • Sample volume is instrument-dependent. Refer to the appropriate Application Sheet for Note: Reagents 1 and 2 are provided as a matched set. They should not be interchanged with specific volumes. components of kits with different lot numbers. • Store the serum or plasma refrigerated at 2–8°C. For transporting, maintain the sample The Emit® 2000 Procainamide Calibrators contain the following stated Procainamide temperature at 2–8°C. Samples can be stored refrigerated at 2–8°C for up to 7 days or stored concentrations: frozen (-20°C) for up to one month. • Pharmacokinetic factors influence the correct time of sample collection after the last drug Calibrator 0 1 2 4 8 16 dose. These factors include dosage form, mode of administration, concomitant drug therapy, 1,2 Procainamide (µg/mL) 0 1.0 2.0 4.0 8.0 16 and biological variations affecting drug disposition. Procainamide (µmol/L) 0 4.3 8.5 17 34 68 • Measure the steady-state serum concentration representing the trough level just before the next scheduled dose. • Human serum or plasma samples should be handled and disposed of as if they were 1 Intended Use potentially infectious.
The Emit® 2000 Procainamide Assay is a homogeneous enzyme immunoassay intended for 6 Procedure use in the quantitative analysis of procainamide in human serum or plasma. These reagents are packaged specifically for use on a variety of AU® Clinical Chemistry Systems. Materials Provided Emit® 2000 Procainamide Assay 2 Summary Reagent 1 Reagent 2 Antiarrhythmic activity of procainamide correlates better with the drug’s concentration in serum Materials Required But Not Provided than with dosage. Therefore, monitoring serum procainamide concentrations helps to achieve an Emit® 2000 Procainamide Calibrators optimum antiarrhythmic effect and reduce the risk of toxicity. Multi-level commercial controls Serum procainamide monitoring is particularly important because the range of procainamide serum concentrations required to achieve an effective and safe antiarrhythmic response is narrow. In addition, patient-to-patient variations in absorption, distribution, metabolism, and Calibration elimination of procainamide make it difficult to predict serum levels from the administered Recalibrate whenever a new lot of reagents is used or as indicated by control results (see Quality dosage, particularly in patients with renal impairment.1,2 Control, below). If a new set of reagents with the same lot number is used, validate the system by assaying controls. The presence of procainamide’s pharmacologically active metabolite, N-acetylprocainamide, complicates the definition of a range of effective serum procainamide concentrations. Since Quality Control patients receiving procainamide for longer than 24 hours are in effect receiving two drugs, plasma N-acetylprocainamide levels should be measured along with procainamide levels.1,2 • Validate the calibration by assaying multi-level (eg, low, medium, and high) controls in every run. Commercial controls are available for this purpose. Ensure that control results fall within Methods historically used to monitor serum procainamide and N-acetylprocainamide acceptable limits as defined by your own laboratory. Once the calibration is validated, run concentrations include immunoassay, gas-liquid chromatography (GLC) assay, and samples. high‑performance liquid chromatography (HPLC) assay.1–3 • Refer to the instrument User’s Guide for appropriate instrument checks and maintenance instructions. 3 Methodology Diluting High Concentration Samples The Emit® 2000 Procainamide Assay is a homogeneous enzyme immunoassay technique To estimate procainamide concentrations above the assay range, patient samples containing used for the analysis of specific compounds in biological fluids.4,5 The assay is based on more than 12 µg/mL (51 µmol/L) procainamide may be diluted with one or two parts distilled or competition between drug in the sample and drug labeled with the enzyme glucose-6-phosphate deionized water or Emit® 2000 Procainamide Calibrator 0. After diluting the sample, repeat the dehydrogenase (G6PDH) for antibody binding sites. Enzyme activity decreases upon binding entire assay sequence and multiply the results by the dilution factor. Some analyzers dilute and to the antibody, so the drug concentration in the sample can be measured in terms of enzyme retest high concentration samples automatically. See the User’s Guide or appropriate Application activity. Active enzyme converts oxidized nicotinamide adenine dinucleotide (NAD) to NADH, Sheet for instructions. resulting in an absorbance change that is measured spectrophotometrically. Endogenous serum G6PDH does not interfere because the coenzyme functions only with the bacterial (Leuconostoc mesenteroides) enzyme employed in the assay. Evaluation and Interpretation of Results Specificity • This assay uses Math Model No. 1. The Emit® 2000 Procainamide Assay measures the total (protein-bound plus unbound) procainamide concentration in serum or plasma. Compounds whose chemical structure or • Results are calculated automatically by the analyzers. No additional manipulation of data is concurrent therapeutic use would suggest possible cross-reactivity have been tested. Only required. procaine cross-reacts with the assay. • The factors that can influence the relationship between procainamide serum or plasma The compounds listed in Table 3 do not interfere with the Emit® 2000 Procainamide Assay when concentrations and clinical response include renal and circulatory function, rate of tested in the presence of 4.0 µg/mL procainamide. Levels tested were at or above maximum acetylation, the severity and type of cardiac arrhythmia, general state of health, and use of physiological or pharmacological concentrations. other drugs. • The concentration of procainamide in serum or plasma depends on the time of the last Table 3 — Compounds That Do Not Interfere drug dose; mode of administration; concomitant drug therapy; sample condition; time of Compound ConcentrationTested (µg/mL) sample collection; and individual variations in absorption, biotransformation, distribution, and excretion. These parameters must be considered when interpreting results.1,2 Acetaminophen 100 Desethyl-N-acetylprocainamide (DENAPA) 100 7 Limitations of the procedure Digoxin 0.1 Diphenylhydantoin 100 Procaine cross-reacts with the assay (See Section 9, Specific Performance Characteristics). Disopyramide 100 Ephedrine 100 8 Expected Values Furosemide 100 The Emit® 2000 Procainamide Assay accurately quantitates procainamide concentrations Glycinexylidide (GX) 100 in human serum or plasma containing 1.0–12 µg/mL (4.3–51 µmol/L) procainamide. Hydrochlorothiazide 100 The desired therapeutic effect is usually achieved in the serum concentration range of 4.0–10 µg/mL (17–43 µmol/L) and the sum of procainamide and N-acetylprocainamide Isoproterenol 100 concentrations is 10–30 µg/mL.1,2 Further, peak concentrations of procainamide above 12 µg/mL Lidocaine 100 (51 µmol/L) are often associated with toxicity.1 Monoethylglycinexylidide (MEGX) 100 Note: To convert from µg/mL to µmol/L procainamide, multiply by 4.25. N-Acetylprocainamide 40 For effective treatment, some patients may require serum levels outside this range. Therefore, the expected range is provided only as a guide, and individual patient results should be N-(2-Diethylaminoethyl) isonicotinamide 100 interpreted in light of other clinical signs and symptoms (see Section 6, Procedure, Evaluation p-Acetamidobenzoic acid 100 and Interpretation of Results). p-Aminobenzoic acid 100 Propranolol 100 9 Specific Performance Characteristics Quinidine 100
The information presented in this section is based on Emit® 2000 Procainamide Assay studies Tocainide 100 performed on the AU400®/AU600® Clinical Chemistry System. Refer to the Application Sheets for other AU Clinical Chemistry Systems and for additional information. Results may vary due Sensitivity to analyzer-to-analyzer differences. The following performance characteristics represent total The sensitivity level of the Emit® 2000 Procainamide Assay is 0.25 µg/mL. This level represents system performance and should not be interpreted to pertain only to reagents. the lowest measurable concentration of procainamide that can be distinguished from 0 µg/mL Endogenous Substances with a confidence level of 95%. No clinically significant interference has been found in samples to which 800 mg/dL hemoglobin, Calibration Stability 1000 mg/dL triglycerides, or 30 mg/dL bilirubin were added to simulate hemolytic, lipemic, or Studies have shown calibration stability of more than two weeks. When proper reagent handling, icteric samples. instrument maintenance, and operating procedures are followed, the calibration should remain Precision stable for at least two weeks. Within-run precision was determined by assaying 20 replicates of each level of a tri-level control. Table 1 summarizes the results. 10 References Table 1 — Within-run Precision 1. Lima JJ, Lewis RP. Procainamide: Therapeutic use and serum concentration monitoring. In: Level 1 Level 2 Level 3 Taylor WJ, Finn AL, eds. Individualizing Drug Therapy: Practical Applications of Drug Monitoring. New York: Gross, Townsend, Frank, Inc; 1981, vol 3, pp 69–88. Mean (µg/mL) 2.47 6.91 12.25 2. Coyle JD, Lima JJ. Procainamide. In: Evans WE, Schentag JJ, Jusko WJ, eds. Applied %CV 1.3 1.7 4.8 Pharmacokinetics: Principles of Therapeutic Drug Monitoring. Washington: Applied Therapeutics, Inc: 1986, pp 682–711. Total precision was calculated according to NCCLS guideline EP5-T2 using data collected from 3. Bauer LA, Black D, Gensler A, et al. Influence of age, renal function, and heart failure controls run in duplicate twice daily over 20 days. Table 2 summarizes the data. on procainamide clearance and n-acetyl-procainamide serum concentrations. Int J Clin Pharmacol Ther Tox. 1989;27(5):213–216. Table 2 — Total Precision 4. Pincus MR, Abraham NZ Jr. Toxicology and therapeutic drug monitoring. In: Henry JB, ed. Level 1 Level 2 Level 3 Clinical Diagnosis and Management by Laboratory Methods, ed 18. Philadelphia: WB Saunders Co; 1991, pp 349–384. Mean (µg/mL) 2.41 6.74 11.13 5. Lam X, Hefner A. Syva® Emit® 2000 Procainamide Assay. Clin Chem 1992;38(6):337. %CV 3.7 3.6 7.9 Abstract.
Comparative Analysis In this study, patient samples were analyzed on the TDx analyzer and on the AU600 Clinical Chemistry System. A summary of the results is as follows:
Slope 1.00 Intercept 0.02 Mean TDx 4.67 AU600 4.71 Correlation Coefficient 0.995 Number 54
2 4K052.3D_B Notes Symbols Key
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Contents
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Level 2010-07_BC
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