creatinine in body fluid
Principle
The Kodak Ektachem Clinical Chemistry Slide (CREA) quantitatively measures creatinine in serum, plasma, or urine. The Single Slide Method (SSM) is a Two-Point Rate Test.
The Kodak Ektachem Clinical Chemistry Slide (CREA) is a dry, multilayered analytical element coated on a clear polyester support.
A 10 uL drop of patient sample is deposited on the slide & is evenly distributed by the spreading layer. Creatinine diffuses to the gel layers where it is hydrolyzed to creatine in the rate- determining step. The creatine thus formed is converted to sarcosine & urea by creatine amidinohydrolase. The sarcosine, in the presence of sarcosine oxidase, is oxidized to glycine, formaldehyde, & hydrogen peroxide. The final reaction involves the peroxidase catalyzed oxidation of a triarylimidazole leuco dye to produce a colored product. Following addition of the sample, the slide is incubated at 37 degrees C. During the initial reaction phase, endogenous creatine in the sample is oxidized. Rate determinations are then made at 3.85 & 5 minutes. The rate of change between the two readings is proportional to the creatinine concentration in the sample. If the endogenous creatine concentration is so high that it cannot be oxidized completely before the first kinetic read time, the result is flagged with a DP error code. The true creatinine concentration can be determined after dilution & reanalysis. The assay wavelength is 670 nm. The assay time is approximately 5 minutes.
Clinical significance
Specimen
The recommended specimen is 10 uL of serum, plasma, or diluted urine. Serum or Plasma Specimens: Collect by standard venipuncture technique. No special patient preparation is necessary. Lithium or sodium heparin may be used as an anticoagulant for plasma specimens. Special Precautions: Potassium oxalate/sodium fluoride, citrate, & EDTA should not be used as anticoagulants. Remove serum or plasma promptly from the clot or cells. Refrigerate specimens at 2-8 degrees C if not analyzed within 4 hours, or freeze specimens at -18 degrees C if analysis is delayed beyond 48 hours. Do not use specimens obtained through catheters used to infuse hyperalimentation fluid. Urine Specimens: Collect specimens by standard laboratory procedure. Keep specimens refrigerated until analysis. Dilute each specimen 40-fold with reagent grade water (1 mL patient plus 19mL of water, then take 1 mL of this dilution & add 1 mL of water) before analysis. Multiply results by 40 to obtain the creatinine value. Dynamic range for urine CREA is 0.1 - 16.5 mg/dL.
Sample Dilution: Dilute samples with creatinine values above the analyzer's dynamic range or that give a 'DP' error code. A 'DP' error code indicates a high background density, usually due to an elevated creatine level. Dilute samples with Kodak Ektachem Solution (7% BSA)/Bovine Serum Albumin. Multiply results by the dilution factor to obtain the original sample's CREA value. Dynamic range for serum or plasma CREA is 0.1 - 14.0 mg/dL.
Minimum sample size is 0.5 milliliter; with an optimum size of 1.0 milliliter or larger.
Interferences
- Preliminary data indicated that hemolysis, icterus and lipemia do not interfere with this method.
- At a creatinine concentration of 1.5 mg/dL, creatine greater than 8 mg/dL will be flagged with a 'DP' error code since highly elevated creatine concentrations may cause excessive background density. Residual bias for unflagged samples due to creatine will be less than 0.15 mg/dL.
- Lidocaine: Patients on long-term lidocaine therapy may show an increase of up to 1.0 mg/dL. Most patients receiving intravenous lidocaine will show an increase of 0.3 mg/dL or less.
- Proline: Patients receiving hyperalimentation fluids containing proline may show an increase of 0.2 mg/dL or less. Do not collect specimens form lines contaminated with hyperalimentation fluid.
- N-acetylcysteine: Patients receiving N-acetylcysteine (Fluimucil, Mucomyst) intravenously have been reported to show a large negative bias. Urine: The following preservatives have been tested & demonstrated an effect of less than 2% on creatinine results: thymol, toluene, boric acid, urine preservative tablets, 12N HCL, NH4OH, bromide, iodide, 5% NaOH, glacial acetic acid.
More general terms
More specific terms
- creatinine in amniotic fluid
- creatinine in blood
- creatinine in CSF
- creatinine in dialysis fluid
- creatinine in gastric fluid
- creatinine in peritoneal fluid
- creatinine in pleural fluid
- creatinine in serum/plasma
- creatinine in serum/plasma postdialysis
- creatinine in serum/plasma predialysis
- creatinine in serum/plasma/blood
- creatinine in stool
- creatinine in synovial fluid
- creatinine in urine
- creatinine in vitreous fluid
Additional terms
Component of
References
- ↑ Kodak Ektachem 700 Analyzer Operator's Manual, Kodak Clinical Products, Rochester, New York.
- ↑ Kodak Ektachem Slide Package Inserts, Kodak Clinical Products Rochester, New York.
- ↑ Kodak Ektachem Training Manual, Kodak Clinical Products, Rochester, New York.
- ↑ Mayo Internal Medicine Board Review, 1998-99, Prakash UBS (ed) Lippincott-Raven, Philadelphia, 1998, pg 620.
- ↑ Medical Knowledge Self Assessment Program (MKSAP) 11, American College of Physicians, Philadelphia 1998.
- ↑ Clinical Diagnosis & Management by Laboratory Methods, 19th edition, J.B. Henry (ed), W.B. Saunders Co., Philadelphia, PA. 1996, pg 11.
- ↑ Prescriber's Letter 9(5):28 2002
- ↑ Creatinine, Body Fluid Laboratory Test Directory ARUP: http://www.aruplab.com/guides/ug/tests/0020509.jsp