title: Catecholamine interference in enzymatic creatinine assays.
abstract: BACKGROUND
  Enzymatic creatinine assays are routinely used in clinical laboratories to provide more accurate estimated glomerular filtration rates and to avoid a perceived lack of analytical specificity associated with picrate (Jaffe) methods. Negative interferences with the enzymatic creatinine assay, which we noted in several patients on dopamine or dobutamine, prompted our further investigation into interference of catecholamines with enzymatic methods.
  
  
  METHODS
  Spiked solutions of dopamine, dobutamine, epinephrine, and norepinephrine were added to pooled sera at catecholamine concentrations consistent with clinically relevant dosing. Creatinine was measured enzymatically on the Roche P-Modular, Ortho Clinical Diagnostics Vitros 350, and Abbott i-STAT. Jaffe methods were performed on the Roche P-Modular and Siemens Dimension RxL. In 10 patients receiving dopamine and/or dobutamine via a venous or arterial line we evaluated and compared the extent of in vivo creatinine interference in paired serum samples obtained by venipuncture and from indwelling catheters.
  
  
  RESULTS
  All catecholamines caused significant negative interference with the Roche enzymatic creatinine assay, most pronounced for dopamine and dobutamine. The Vitros enzymatic assay demonstrated slight negative interferences, and i-STAT enzymatic and Jaffe methods were unaffected by the presence of catecholamines. Significant (P < 0.001) differences in creatinine concentrations by Roche enzymatic vs Jaffe methods were observed in venipuncture specimens compared with arterial or venous catheter specimens, suggesting dopamine and dobutamine reversibly adhere to the catheter lumen.
  
  
  CONCLUSIONS
  Negative interferences were pronounced for Roche enzymatic results in blood samples obtained from indwelling catheters, a phenomenon not observed in peripheral draws. Physicians and laboratorians should be alert to the possibility of a falsely low creatinine result and reevaluate questionable samples using a method unaffected by catecholamines.
authors: Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, Minnesota 55905, USA.
authors: Amy K
authors: AK
authors: Saenger
authors: Christina
authors: C
authors: Lockwood
authors: Christine L
authors: CL
authors: Snozek
authors: Thomas C
authors: TC
authors: Milz
authors: Brad S
authors: BS
authors: Karon
authors: Mitchell G
authors: MG
authors: Scott
authors: Allan S
authors: AS
authors: Jaffe
mesh_terms: D000328:Adult; D001774:Blood Chemical Analysis / Q000379:methods*; D002395:Catecholamines / Q000494:pharmacology* / Q000627:therapeutic use; D003404:Creatinine / Q000097:blood* / Q000378:metabolism; D005919:Glomerular Filtration Rate; D006801:Humans; D007674:Kidney Diseases / Q000188:drug therapy / Q000503:physiopathology; D007677:Kidney Function Tests / Q000379:methods*; D008297:Male
chemical_list: D002395:Catecholamines; D003404:Creatinine