Applicable To Employees of Gundersen Boscobel Area Hospital Laboratory and Gundersen Palmer Lutheran Hospital and Clinics Laboratory.

Transcription

1 Subject Creatinine COBAS C311 Index Number Lab-8814 Section Laboratory Subsection Regional/Affiliates Location Category Departmental Contact Tilleraas, Betty Last Revised 1/17/2018 References Required document for Laboratory Accreditation by the College of American Pathologists (CAP), Centers for Medicare and Medicaid Services (CMS) and/or COLA. Applicable To Employees of Gundersen Boscobel Area Hospital Laboratory and Gundersen Palmer Lutheran Hospital and Clinics Laboratory. Detail PRINCIPLE: COBAS Creatinine is an In vitro test for the quantitative determination of creatinine concentration in human serum, plasma and urine on Roche/Hitachi cobas c systems. This enzymatic method is based on the conversion of creatinine with the aid of creatininase, creatinase, and sarcosine oxidase to glycine, formaldehyde and hydrogen peroxide. Catalyzed by peroxidase the liberated hydrogen peroxide reacts with 4-aminophenazone and HTIBa to form a quinone imine chromogen. The color intensity of the quinone imine chromogen formed is directly proportional to the creatinine concentration in the reaction mixture. CLINICAL SIGNIFICANCE: Creatinine is produced endogenously from creatine and creatine phosphate as a result of muscle metabolic processes. It is excreted by glomerular filtration during normal renal function. Creatinine assays are conducted for diagnostic purposes, for therapeutic monitoring of acute and chronic renal diseases, and for monitoring kidney dialysis. The urinary creatinine concentration can also be used as a reference parameter for analyte excretion. SPECIMEN: Universal Precautions apply. Plasma (preferred -Acceptable anticoagulant: Li-heparin), Serum or Urine Stability in serum/plasma: 7 days at C 7 days at 2-8 C 3 months at (-15)-(-25) C Stability in Urine (without preservative): 2 days at C Lab-8814 Creatinine COBAS C311 Page 1 of 5

2 6 days at 2-8 C 6 months at (-15)-(-25) C Stability in Urine (with preservative): 3 days at C 8 days at 2-8 C 3 weeks at (-15)-(-25) C The only acceptable urine preservatives are glacial acetic acid, hydrochloric acid and boric acid. Therefore the same collection can be used for catecholamine and creatinine. REAGENTS/MATERIALS: R1 TAPS buffer (N-Tris(hydroxymethyl)methyl-3-aminopropanesulfonic acid): 30 mmol/l, ph 8.1; creatinase (microorganisms): 332 µkat/l; sarcosine oxidase (microorganisms): 132 µkat/l; ascorbate oxidase (microorganisms): 33 µkat/l; catalase (microorganisms): 1.67 µkat/l; HTIB: 1.2 g/l; detergents; preservative R3 TAPS buffer: 50 mmol/l, ph 8.0; creatininase (microorganisms): 498 µkat/l; peroxidase (horseradish): 16.6 µkat/l; 4-aminophenazone: 0.5 g/l; potassium hexacyanoferrate (II): 60 mg/l; detergent; preservative R1 is in position B and R3 is in position C. Reagent Precautions: Exercise the normal precautions required for handling all laboratory reagents. Reagent Storage and Stability: CREP2 Shelf life at 2-8 C: On-board in use and refrigerated on the analyzer: Diluent NaCl 9 % Shelf life at 2-8 C: On-board in use and refrigerated on the analyzer: See expiration date on cobas c pack label. 8 weeks See expiration date on cobas c pack label. 12 weeks EQIUPMENT/INSTRUMENTATION: COBAS C311 Calibration: Calibrators S1: H 2 O S2: C.f.a.s. Calibration mode Linear Calibration frequency Blank calibration after 4 weeks during shelf life Lab-8814 Creatinine COBAS C311 Page 2 of 5

3 2-point calibration 1. At initial installation 2. If necessary after instrument service or repair 3. If dictated by quality control results 4. If instructed to do so by Roche support personnel 5. With each new reagent lot number QUALITY CONTROL: Quality Control Frequency: Two levels of Quality Control should be performed at a minimum: 1. Once very twenty-four hours 2. If a new cassette of reagent is put in use 3. If a calibration is performed. Implementation Refer to the C311 User s Manual located in the laboratory. PROCEDURE NOTES: Results are reported to two decimal places in mg/dl. AMR (Analytic Measurement Range): Serum or Plasma: mg/dl Extended Range Serum or plasma mg/dl with automatic 1: 4 post dilution Urine: mg/dl mg/dl with automatic post dilution CALCULATIONS: N/A INTERPRETATION: Expected Ranges: Serum/Plasma: Adult Females mg/dl Adult Males mg/dl 0 4 days mg/dl 4 days 2 years mg/dl 2-12 years mg/dl years mg/dl 24 hour urine: Females Males mg/24 h mg/24 h Lab-8814 Creatinine COBAS C311 Page 3 of 5

4 Creatinine Clearance: Females (0-40 yrs.)* Males (0-40 yrs.)* ml/min/1.73m ml/min/1.73m2 *NOTE: Clearance rate drops 6 ml/min for each decade over 40 years. For diagnostic purposes, the test findings should always be assessed in conjunction with the patient s medical history, clinical examination and other findings. LIMITATIONS: Criterion: Recovery within ± 10 % of initial values at creatinine concentrations of 80 µmol/l (0.9 mg/dl) in serum and 2500 µmol/l (28.3 mg/dl) in urine. Serum/plasma Icterus: No significant interference up to an I index of 15 for conjugated bilirubin and 20 for unconjugated bilirubin (approximate conjugated bilirubin concentration: 257 µmol/l or 15 mg/dl; approximate unconjugated bilirubin concentration: 342 µmol/l or 20 mg/dl). Hemolysis: No significant interference up to an H index of 800 (approximate hemoglobin concentration: 497 µmol/l or 800 mg/dl). Lipemia (Intralipid): No significant interference up to an L index of There is a poor correlation between the L index (corresponds to turbidity) and triglycerides concentration. Ascorbic acid: < 1.70 mmol/l or < 300 mg/l does not interfere. Drugs: No interference was found at therapeutic concentrations using common drug panels. Exceptions: Rifampicin, Levodopa and Calcium dobesilate (e.g. Dexium) cause artificially low creatinine results. Dicynone (Etamsylate) at therapeutic concentrations may lead to false-low results. N-ethylglycine at therapeutic concentrations and DL-proline at concentrations * 1 mmol/l (* 115 mg/l) give falsely high results. No significant interference up to a creatine level of 4 mmol/l (524 mg/l). Hemolyzed samples from neonates, infants or adults with HbF values * 600 mg/dl interfere with the test. 2-Phenyl-1,3-indandion (Phenindion) at therapeutic concentrations interferes with the assay. In very rare cases, gammopathy, in particular type IgM (Waldenström's macroglobulinemia), may cause unreliable results. Estimation of the glomerular filtration rate (GFR) on the basis of the Schwartz formula can lead to an overestimation. For diagnostic purposes, the results should always be assessed in conjunction with the patient's medical history, clinical examination and other findings. Lab-8814 Creatinine COBAS C311 Page 4 of 5

5 Urine Icterus: No significant interference up to an approximate conjugated bilirubin concentration of 1197 µmol/l (70 mg/dl). Hemolysis: No significant interference up to an approximate hemoglobin concentration of 621 µmol/l (1000 mg/dl). Ascorbic acid < 22.7 mmol/l (< 4000 mg/l), glucose < 120 mmol/l (< 2162 mg/dl) and urobilinogen < 676 µmol/l (< 40 mg/dl) do not interfere. Drugs: No interference was found at therapeutic concentrations using common drug panels. Exceptions: Calcium dobesilate (e.g. Dexium), Levodopa and *-methyldopa cause artificially low creatinine results. Dicynone (Etamsylate) at therapeutic concentrations may lead to false-low results. High homogentisic acid concentrations in urine samples lead to false results. Special Wash Programming: The use of special wash steps is mandatory when certain test combinations are run together on Roche/Hitachi cobas c systems. The latest version of the carry-over evasion list can be found with the NaOHD/SMS/Multiclean/SCCS or the NaOHD/SMS/SmpCln1+2/SCCS Method Sheets. For further instructions refer to the operator's manual. Where required, special wash/carry-over evasion programming must be implemented prior to reporting results with this test. REVIEW AND CHANGES: This document and all attached forms should be reviewed optimally on an annual basis, with two years as the maximum review date. Review will be done by the Technical Leader, Supervisor, Manager, Medical Director or other designated person. Changes require retyping the document, and review by the Medical Director. REFERENCES: 1. COBAS C311 User s manual 2. COBAS C311 Creatinine Method Sheet 3. COBAS C311 Method Manual Lab-8814 Creatinine COBAS C311 Page 5 of 5