August 1984

Artifactual Elevation of Serum Creatinine Level due to Fasting

Author Affiliations

From the Divisions of General Internal Medicine (Drs Mascioli and Bantle) and Endocrinology and Metabolism (Dr Hoogwerf), the Department of Medicine and the Department of Laboratory Medicine and Pathology (Prof Freier), University of Minnesota, Minneapolis.

Arch Intern Med. 1984;144(8):1575-1576. doi:10.1001/archinte.1984.00350200067009

• Abnormal serum creatinine (1.6 mg/dL) and creatinine clearance (33 mL/min) levels found in a 50-year-old woman during fasting were corrected with refeeding. Five healthy subjects who fasted for 96 hours demonstrated an increase in their mean serum creatinine level from 1.0±0.08 to 1.7±0.11 mg/dL as determined by Jaffé's method. This increase was probably an artifact caused by the rise in the serum acetoacetate level during fasting. The serum creatinine level determined by an enzymatic method and serum urea nitrogen level did not change substantially during the fast. We conclude that fasting may cause an artifactual increase in the serum creatinine level determined by Jaffé's method, the method used by most clinical laboratories.

(Arch Intern Med 1984;144:1575-1576)