2. Reagent Store at 2-8ºC. 3. Standard - - Store at 2-30ºC.

Transcription

1 UREA UV - Liquiform Insert Ref.:104 Intended use. Enzymatic system for urea determination in serum, plasma and urine by photometry in ultraviolet using two-point, fixed-time kinetic method. Professional use. [For in vitro diagnostic only] Test principle. Urea determination involves the following reaction: Urease Urea + H O 2NH + Co Ammonia reacts with 2-ketoglutarate and NADH in a reaction catalyzed by glutamate dehydrogenase (GLDH), promoting oxidation of NADH to NAD. The consequent reduction of absorbance measured at 340 nm is proportional to the urea concentration in the sample. 2-ketoglutarate + NH + NADH 3 GLDH L-Glutamate + NAD Summary. There are several methods for urea determination, but the methods using coupling-reaction are more convenient and extensively used in clinical laboratory. The system presents linearity up to 300 mg/dl reducing drastically the tests repetition in high values. Labtest product does not suffer interference by slightly increased values of bilirubin, hemoglobin, and triglycerides. The substances for this reaction are distributed properly in two reagents in order to get more stability in the original liquid form and keep the optimum operational conditions, allowing the direct use of the reagents in automatic systems. The monoreagent method can be applied by using one Work Reagent, 28 days stable if stored at 2-8ºC, reaching appropriated performance even in low requests of the test. The system also allows preparing the volume of the Work Reagent needed to one measure of urea concentration. This method is easily applied to most automated and semi-automated systems which are able to measure the absorbance at 340 nm. Methodology. Enzymatic UV. Reagents 1. Reagent Store at 2-8ºC. Reagent label bears expiration date. Buffer ph 10.0 ( mmol/l); 2-ketoglutarate (16 mmol/l); NADH (300 mol/l); sodium azide (30.8 mmol/l) and surfactant. 2. Reagent Store at 2-8ºC. Reagent label bears expiration date. Buffer ph 8.0 (380 mmol/l); urease ( U/L); GLDH ( 3750 U/L); sodium azide (14.6 mmol/l) and surfactant. 3. Standard - - Store at 2-30ºC. Reagent label bears expiration date. Urea 70 mg/dl and sodium azide (7.7 mmol/l). Precautions and warnings Disposal of all waste material should be in accordance with local guidelines. The usual security cares should be applied on the reagent handling. The reagents and the standard contain sodium azide as preservative. Avoid ingestion. In case of eyes contact, immediately flush eyes with plenty of water and get medical assistance. Sodium azide may react with lead and copper plumbing to form highly explosive metal azides. On disposal, flush with a large volume of water to prevent azide accumulation. Storage and stability. Unopened reagents, when stored at indicated temperature, are stable up to expiration date shown on the label. In order to avoid evaporation of the Standard, keep the bottle tightly closed. Deterioration. Microbial or chemical contamination may decrease reagents stability. Urea UV Liquiform is not suitable for use if Working Reagent has an absorbance 1.0 at 340 nm when measured versus water as reference, in case of contaminations signs or if it develops turbidity. Sample Use serum or plasma (fluoride, heparin, EDTA) and urine. Fluoride concentration should not be over 3 mg/dl because high fluoride concentration is urease inhibitor. 01 English - Ref.: 104

2 The use of the anticoagulant Glistab (Labtest Ref.: 29) allows the collection of only one sample to the urea, glucose and creatinine measurements. Urea is reportedly stable in serum or plasma for about 12 hours at 15-25ºC and 3 days at 2-8ºC. Do not use the samples with microbial contaminations signs. The 24 hours urine must be collected in a flask containing 2.0 ml of 50% (v/v) HCl (6M) and centrifuge before using. No known test method can offer complete assurance that human blood samples will not transmit infectious diseases. Therefore, all blood derivatives should be considered potentially infectious. Interference Bilirubin up to mg/dl, hemoglobin up to 300 mg/dl and triglycerides up to 1800 mg/dl do not interfere significantly. Ammonia contamination from water, bottles and environment may yield false increased results. Avoid smoking near to the laboratory where the measurement is done. Materials required not provided 1. Photometer capable of keeping the cuvette temperature at 37ºC, and meansuring absorbance at 340 nm. 2. Pipettes to measure reagents and samples. 3. Timer. Preparing the working reagent. Use one bottle of Reagent 1 and Reagent 2 for preparing Working Reagent. Transfer all the contents of one Reagent 2 bottle to one Reagent 1 bottle and mix by inversion. The Working Reagent is stable 2 days at 15-25ºC and 28 days at 2-8ºC when no chemical or microbial contamination occurs. Optionally, a lower volume of the Working Reagent may be prepared by using the volume proportion 4:1 of the Reagent 1 and Reagent 2, respectively. Procedure In order to measuring urea in urine sample, dilute the sample 1:50 (0.1 ml of urine ml distilled or deionized water). Multiply the result by Adjust the temperature of photometer to ºC and the wavelength at 340 nm. Zero the equipment with deionized water. 2. Into one tube labeled "Unknown" or "Standard" add 1.0 ml of Working Reagent and incubate at working temperature for 1 minute. 3. Add 0.01 ml of Sample or Standard, mix and transfer immediately to a cuvette at ºC. 5. Use the difference of the absorbance ( A) between both times (A30-A 90) for calculating the results. Calibration System Traceability The Standard is traceable to 912 Standard Reference Material (SRM) of the National Institute of Standards and Technology (NIST). Manual calibrations Obtain a new calibration factor weekly. Obtain a new calibration factor when the internal control indicates or after reagent lot change. Automatic Systems Blank of reagents: water or 0.85% NaCl; Standards: Calibra Series (Labtest calibrator for automated systems), which are traceable to NIST SRM 912. Calibration frequency Two or three point calibration after reagent lot change; Two or three point calibration when the internal quality control indicates. Quality control For quality control use Qualitrol H Level 1 and Qualitrol H Level 2 or other suitable control material. The limits and control interval must be adapted to the laboratory requirements. Each laboratory should establish corrective actions to be taken if values fall outside the control limits. Calculations A unknown Urea (mg/dl) = x 70 A standard Due the great reproductive results of the assay system, it is possible to use the factor method: Calibration factor = 70 A standard Urea (mg/dl) = A Unknown x Factor Urine - Urea (mg/24 hours) = Conversion to g/24 hours unit: Urea (g/24 hours) = mg/dl x Urine volume (ml) Urea (mg/24 hours) Start the timer and measure the absorbance at 30 and 90 seconds. 02 English - Ref.: 104

3 Measurement/reportable range Up to 300 mg/dl. If urea concentration exceeds 300 mg/dl, the sample must be diluted with 0.85% NaCl. Multiply the result by the appropriate dilution factor. Expected range. Each laboratory should evaluate the transferability of the expected values to its own patient population and, if necessary, estimate its own reference interval. Serum or Plasma Children and Teenagers 6 Age 1 day - 12 months 1-13 years mg/dl The total error (random error + systematic error) estimated at a decision level of 56 mg/dl is 2.5 mg/dl or 4.2% and at a decision level of 107 mg/dl is 5.0 mg/dl or 4.7%. The result indicates that the method meets the specification for total error (15.7%) based on the componentes of the biological variation. Analytical sensitivity. Detection limit: 0.94 mg/dl. The detection limit represents the lowest measurable urea concentration that can be distinguished from zero. It is calculated as two standard deviations of replicates of one sample without urea. Effects of matrix dilution. Two samples with values equal to 355 and 360 mg/dl were used to evaluate the system response in the matrix dilutions with NaCl 150 mmol /L (0.85%). Using dilution factors ranging from 2 to 4, recoveries between and 111.4% were found. The systematic errors found are significantly smaller than the total error of the specification based on the componentes of the biological variation. Serum or Plasma Age Adults mg/dl Notes 1. The material cleaning and drying are fundamental factors to the reagent stability and to obtain correct results. Urine (all ages): g/24 hours Conversion: Conventional Unit (mg/dl) x = Unit IS (mmol/l). Performance characteristics 7 Recovery studies. In two samples with urea concentrations of 37 mg/dl were added different quantities of the analyte. Subsequent analyses provided recoveries ranging from 95 to 98%. The mean proportional systematic error at 56 mg/dl and mg/dl decision level was 1.9 mg/dl and 3.6 mg/dl, respectively. Method comparison. A group of samples were assayed by the proposed method and a similar technique. Samples urea values ranged from mg/dl. The comparisons yielded a correlation coefficient of and regression equation was y = 0.975x Imprecision - Within run 2. The deionized or distilled water in the laboratory to prepare reagents, use in the measurements and for final glass washing must have resistivity 1 megaohm.cm, or conductivity 1 microsiems/cm and silicates concentration must be 0.1mg/L. 3. It is suggested to consult < in order to review physiopathological source and drugs interference in results and methodology. References rd 1. Bergmeyer HU. Methods of Enzymatic Analysis, v. 8, 3 ed, Deerfield Beach: Verlag Chemie, 1985; Hallet CJ, Cook JGM. Clin Chim Acta 1971; 35: Tonks DB. Quality Control in Clinical Laboratories, Warner-Chilcott Laboratories, Diagnostics Reagents Division, Scarborough, Canada, Sample 1 Sample 2 N Mean SD %CV Sociedad Española de Bioquímica Clínica y Patología Molecular, Base de Datos de Variación Biológica. Disponível em:< (accessed on 05/08). Imprecision - Run-to-run 5. Westgard JO, Barry PL, Hunt MR, Groth T. Clin Chem. 1981, 27: Sample 1 Sample 2 N Mean SD %CV Soldin SJ, Brugnara C, Wong EC: Pediatric Reference Ranges, 5a. edição, Washington: AACC Press, 05: Labtest: data on file. 03 English - Ref.: 104

4 Presentation Product Referencia Contents Ureia UV Liquiform 104-4/ / x 40 ml 4 x 10 ml 1 x 5 ml 2 x 0 ml 2 x 50 ml Labtest Diagnóstica S.A. CNPJ: / Av. Paulo Ferreira da Costa, Vista Alegre - CEP Lagoa Santa. Minas Gerais Brasil - Customer Service customerservice@labtest.com.br 1 x 5 ml Ureia UV Liquiform Labmax 560/ / x 35 ml 4 x 9 ml 1 x 5 ml Revision: July, 14 Ref.: Copyright by Labtest Diagnóstica S.A. Reproduction under previous autorization Application procedures using Urea UV systems are available for various automated systems. The number of tests in automated systems depends of the programmed parameters. Customer information [Warranty conditions] Labtest Diagnóstica warrants the performance of this product under the specifications until the expiration date shown in the label since the application procedures and storage conditions, indicated on the label and in this insert, have been followed correctly. 04 English - Ref.: 104

5 05 English - Ref.: 104

6 06 English - Ref.: 104