4 REAGENTS Reagents contain the following substances: Mouse monoclonal antibodies reactive to quinidine (1.35 µg/mL), glucose-6-phosphate (22 mM), nicotinamide adenine dinucleotide (18 mM), quinidine labeled with glucose-6-phosphate dehydrogenase (0.41 U/mL), 0.1% sodium azide, Tris buffer, Quinidine Assay preservatives, and stabilizers Precautions • For in vitro diagnostic use. July 2012 4Q052.2D_C • Contains nonsterile mouse monoclonal antibodies. • Assay components contain sodium azide, which may react with lead and copper plumbing to See shaded sections: form highly explosive metal azides. If waste is discarded down the drain, flush it with a large Updated information from August 2010 edition. volume of water to prevent azide buildup. • Do not use the kit after the expiration date. • This kit contains streptomycin sulfate. Please dispose of appropriately. • Turbid or yellow reagents may indicate contamination or degradation and must be discarded. Safety data sheets (MSDS/SDS) available on www.siemens.com/diagnostics Catalog Quantity/ Preparation of Reagents Number Product Description Volume The Emit® 2000 Quinidine Assay reagents are provided ready to use; no preparation is OSR4Q229 Emit® 2000 Quinidine Assay necessary. OSR4Q518 R1 (Antibody/Substrate Reagent 1) 2 x 23 mL Storage of Assay Components OSR4Q548 R2 (Enzyme Reagent 2) 2 x 13 mL • 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. 4Q109UL Emit® 2000 Quinidine Calibrators* 1 x 5 mL†, 5 x 2 mL • Unopened reagents are stable until the expiration date printed on the label if stored upright at 2–8°C. *Required for calibrating the Emit ® 2000 Quinidine Assay. Sold separately. • Do not freeze reagents or expose them to temperatures above 32°C. †Additional negative calibrator is provided. Note: Reagents and calibrators are shipped ready to use in liquid form. 5 SPECIMEN COLLECTION AND PREPARATION Note: Reagents 1 and 2 are provided as a matched set. They should not be interchanged with components of kits with different lot numbers. • Each assay requires serum or plasma. Whole blood cannot be used. The anticoagulants The Emit® 2000 Quinidine Calibrators contain the following stated quinidine concentrations: heparin, citrate, oxalate, and EDTA have been tested and may be used with this assay. Some sample dilution may occur when samples are collected in tubes containing citrate Calibrator 0 0.5 1 2 4 8 anticoagulant. The amount of dilution and the possible need to correct for it should be considered when interpreting assay results for these samples. Quinidine (µg/mL) 0 0.5 1.0 2.0 4.0 8.0 • Sample volume is instrument-dependent. Refer to the appropriate Application Sheet for Quinidine (µmol/L) 0 1.5 3.1 6.2 12 25 specific volumes. • Store the serum or plasma refrigerated at 2–8°C. For transporting, maintain the sample temperature at 2–8°C. Samples can be stored refrigerated at 2–8°C for up to 7 days or stored 1 INTENDED USE frozen (-20°C) for up to 1 month. • Pharmacokinetic factors influence the correct time of sample collection after the last drug The Emit® 2000 Quinidine Assay is a homogeneous enzyme immunoassay intended for use in dose. These factors include dosage form, mode of administration, concomitant drug therapy, the quantitative analysis of quinidine in human serum or plasma. These reagents are packaged and biological variations affecting drug disposition.1–3 specifically for use on a variety of AU® Clinical Chemistry Systems. • Measure the steady-state serum concentration representing the trough level just before the next scheduled dose. 2 SUMMARY • Human serum or plasma samples should be handled and disposed of as if they were potentially infectious. Monitoring serum quinidine concentrations, along with careful clinical assessment, is the most effective means of achieving an optimum antiarrhythmic effect and reducing the risk of toxicity for the following reasons: 6 PROCEDURE • Serum quinidine concentrations correlate better with pharmacologic activity than does dosage.1,2 Materials Provided Emit® 2000 Quinidine Assay • The quinidine dosage required to control cardiac arrhythmias varies substantially in different Reagent 1 patients and in the same patient at different times. These variations are due to differences Reagent 2 inabsorption and metabolism and to the influences of disease states and coadministered drugs.1–3 Materials Required But Not Provided • Quinidine is safe and effective only in a narrow range of serum concentrations.1–3 Emit® 2000 Quinidine Calibrators Multi-level commercial controls • The symptoms of serious quinidine toxicity can mimic those of an ineffectively controlled cardiac disorder.1 Calibration Methods historically used to monitor serum quinidine concentrations include spectroscopic assay, chromatographic assay, and immunoassay.1, 2, 4 Recalibrate whenever a new lot of reagents is used or as indicated by control results (see Quality Control, below). If a new set of reagents with the same lot number is used, validate the system by assaying controls. 3 METHODOLOGY Quality Control The Emit® 2000 Quinidine Assay is a homogeneous enzyme immunoassay technique used for 1. Validate the calibration by assaying multi-level controls. Commercial controls are available for the analysis of specific compounds in biological fluids.4,5 The assay is based on competition this purpose. Ensure that control results fall within acceptable limits as defined by your own between drug in the sample and drug labeled with the enzyme glucose-6-phosphate laboratory. Once the calibration is validated, run samples. dehydrogenase (G6PDH) for antibody binding sites. Enzyme activity decreases upon binding 2. Follow government regulations or accreditation requirements for quality control frequency. to the antibody, so the drug concentration in the sample can be measured in terms of enzyme At least once each day of use, analyze two levels of Quality Control (QC) material with known activity. Active enzyme converts oxidized nicotinamide adenine dinucleotide (NAD) to NADH, Quinidine concentrations. Follow your laboratory internal QC procedures if the results resulting in an absorbance change that is measured spectrophotometrically. Endogenous serum obtained are outside acceptable limits. G6PDH does not interfere because the coenzyme functions only with the bacterial (Leuconostoc mesenteroides) enzyme employed in the assay. 3. Refer to the instrument operator’s manual for appropriate instrument checks. Diluting High Concentration Samples Comparative Analysis To estimate quinidine concentrations above the assay range, patient samples containing more In this study, samples from patients were analyzed on the TDx analyzer and on the AU600 Clinical than 8.0 µg/mL (25 µmol/L) quinidine may be diluted with one or two parts distilled or deionized Chemistry System. A summary of the results is as follows: water or Emit® 2000 Quinidine Calibrator 0. After diluting the sample, repeat the entire assay sequence and multiply the results by the dilution factor. Some analyzers dilute and retest high Table 3 — Comparative Analysis Results concentration samples automatically. See the analyzer User’s Guide or appropriate Application Sheet for instructions. Slope 1.02 Intercept -0.06 Evaluation and Interpretation of Results Mean TDx 2.85 • This assay uses Math Model No. 1. AU600 2.86 • The factors that can influence the relationship between quinidine serum or plasma concentrations and clinical response include the type and severity of arrhythmia, liver Correlation Coefficient 0.98 1–3 function, kidney function, general state of health, and use of other drugs. Number 53 • The concentration of quinidine in serum or plasma depends on the time of the last drug dose; mode of administration; concomitant drug therapy; sample condition; time of sample collection; and individual variations of absorption, distribution, biotransformation, and Specificity excretion. These parameters must be considered when interpreting results.1–3 The Emit® 2000 Quinidine Assay measures the total (protein-bound plus unbound) quinidine concentration in serum or plasma. In addition, dihydroquinidine (DHQ) makes a small, but • Results of this test should always be interpreted in conjunction with the patient’s medical measurable, contribution to the assayed value (see Section 8, Expected Values). history, clinical presentation and other findings. Compounds whose chemical structure or concurrent therapeutic use would suggest possible cross-reactivity have been tested. o-Desmethylquinidine (DMQ), a minor metabolite of quinidine, 7 LIMITATIONS OF THE PROCEDURE cross-reacts with this assay. The compounds listed in Table 4 do not interfere with the Emit® 2000 Quinidine Assay when o-Desmethylquinidine (DMQ), a minor metabolite of quinidine, cross-reacts with this assay (see tested in the presence of 2.0 µg/mL quinidine. Levels tested were at or above maximum Section 9, Specific Performance Characteristics, Specificity). physiological or pharmacological concentrations. Table 4 — Compounds That Do Not Interfere 8 EXPECTED VALUES Concentration Tested Concentration Tested Compound (µg/mL) Compound (µg/mL) The Emit® 2000 Quinidine Assay accurately quantitates quinidine concentrations in human serum or plasma containing 0.5–8.0 µg/mL (1.5–25 µmol/L) quinidine. Dihydroquinidine Structurally Related Compounds Structurally Unrelated Compounds 6,7 (DHQ), a constituent of pharmaceutical quinidine preparations, has antiarrhythmic activity