Unexpected Creatinine Values.
An 88-year-old man was admitted for acute coronary syndrome associated with renal dysfunction. Ten hours after admission, the patient was found to be hypotensive and treated with intravenous dobutamine injected via a central line. Enzymatically measured creatinine concentration (Roche Diagnostics, COBAS 8000) was significantly decreased 24 h after admission (Table 1), inconsistent with clinical features and blood urea nitrogen concentration. This unexpected decrease of creatinine was confirmed with another blood sample drawn from the central line.
QUESTIONS TO CONSIDER
1. What factor(s) account for the falsely decreased creatinine concentration in this patient?
2. What is the mechanism of the interference?
3. What strategies could be used to follow this patient's renal function?
Unexpectedly decreased creatinine concentrations have been described following catecholamine injection. These discrepancies were seen with central catheter drawn samples (1) and with enzymatic creatinine assays using phenazone substrate. Catecholamine reacts with phenazone in the presence of peroxidase, generating a less efficient chromophore and thus a negative interference (2). To avoid this interference, patient monitoring should be performed by drawing samples from peripheral veins, by measuring creatinine using Jaffe methods, and/or by following blood urea nitrogen concentrations (1,3).
Author Contributions: All authors confirmed they have contributed to the intellectual content of this paper and have met the following 3 requirements: (a) significant contributions to the conception and design, acquisition of data, or analysis and interpretation of data; (b) drafting or revising the article for intellectual content; and (c) final approval of the published article.
Authors' Disclosures or Potential Conflicts of Interest: No authors declared any potential conflicts of interest.
(1.) Saenger A, Lockwood C, Snozek C, Milz T, Karon B, Scott M, Jaffe A. Catecholamine interference in enzymatic creatinine assays. Clin Chem 2009; 55:1732-6.
(2.) Karon B, Daly T, Scott M. Mechanisms of dopamine and dobutamine interference in biochemical tests that use a peroxide and peroxidase to generate chromophore. Clin Chem 1998; 44:155-60.
(3.) PetridesA, Ness M, Judge D, Sokoll L, Marzinke M. Fluctuating creatinine inthecardiac unit. Clin ChimActa 2015; 447:52-4.
Jean-Baptiste Oudart, [1,2] * Imad Dali Braham,  and Francois-Xavier Maquart [1,2]
 CHU de Reims, Laboratoire Central de Biochimie, Hopital Robert Debre, Reims, France;
 Universite de Reims Champagne-Ardenne, UMR CNRS/URCA 7369, Faculte de Medecine, Reims, France.
* Address correspondence to this author at: Laboratoire Central de Biochimie, Hopital Robert Debre, CHU de Reims, Avenue du General Koenig, 51100 Reims, France. Fax (0)326788539; e-mail firstname.lastname@example.org.
Received July 1,2016; accepted July 26,2016.
Table 1. Laboratory test results. Reference Interval Admission Creatinine 59-104 [micro]mol/L 504 [micro]mol/L (enzymatic assay) 0.67-1.18 mg/dL 5.7 mg/dL Blood urea nitrogen 2.2-7.2 mmol/L 40.5 mmol/L 13-43 mg/dL 243 mg/dL 24 h after admission Creatinine 107 [micro]mol/L (enzymatic assay) 1.21 mg/dL Blood urea nitrogen 37.4 mmol/L 225 mg/dL
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|Title Annotation:||the Clinical Chemist: What Is Your Guess?|
|Author:||Oudart, Jean-Baptiste; Braham, Imad Dali; Maquart, Francois-Xavier|
|Date:||Dec 1, 2016|
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