A Case of Interference in Serum Creatinine Levels by Post-Operational Cefazolin Administration

Serum creatinine is a crucial surrogate marker for estimating the glomerular filtration rate.Cefazolin, a first-generation cephalosporin, is widely used intravenously for post-operational prophylaxis; however, it interferes with the Jaffe method, which is used to measure serum creatinine levels.Such interference is usually negligible at normal clinical concentrations achieved upon administration of cefazolin; thus, its effect is rarely seen in samples collected from patients.Here, we report a case with falsely increased creatinine levels caused by post-operational cefazolin administration.The serum sample from the patient was collected at the same time as intravenous cefazolin infusion seven hours post-operation.An abrupt, false increase in creatinine levels from 1.26 mg/dL to 6.65 mg/dL confused the clinician and they proceeded with evaluation for acute kidney injury.This resulted in the patient receiving unnecessary administration of furosemide and undergoing radiologic examinations including chest x-ray, abdominal x-ray, and a non-contrast kidney/bladder CT.Results of creatinine measurements using five different assays, of which the Jaffe or modified Jaffe method were used for four and the enzymatic method was used for one, revealed that only the platform using the enzymatic method did not show falsely elevated creatinine concentrations.This case emphasizes the importance of delta and limit checks, and the comprehensive management of patients through communication between clinicians and laboratory physicians.