Clinical Chemistry
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Clinical Chemistry 55: 1732-1736, 2009. First published July 9, 2009; 10.1373/clinchem.2009.127373
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(Clinical Chemistry. 2009;55:1732-1736.)
© 2009 American Association for Clinical Chemistry, Inc.

Brief Communications

Catecholamine Interference in Enzymatic Creatinine Assays

Amy K. Saenger1,a, Christina Lockwood2, Christine L. Snozek1, Thomas C. Milz1, Brad S. Karon1, Mitchell G. Scott2 and Allan S. Jaffe1,3

1 Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, Minnesota;2 Department of Laboratory Medicine and Pathology, Washington University School of Medicine, St. Louis, Missouri;3 Cardiovascular Division, Department of Medicine, Mayo Clinic, Rochester, Minnesota;

aaddress correspondence to this author at: Department of Laboratory Medicine and Pathology, Hilton Bldg. 370, Mayo Clinic, 200 First St. SW, Rochester, MN 55905. Fax +507-538-7060; e-mail saenger.amy{at}mayo.edu.


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.






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