Artifactually elevated serum creatinine determination after nitromethane ingestion

• Published in: Clinical toxicology (Philadelphia, Pa.) Pa.), 2005-10, Vol.43 (6), p.660-661
• Main Authors: Mell, H K, Lintner, C P, Sztajnkrycer, MD
• Format: Article
• Language: English
• ISSN: 1556-3650

In contrast to serum electrolyte determination, which most commonly uses a direct ion-selective electrode (ISE) technique, serum creatinine is typically measured through a complex reaction with alkaline picrate, referred to as the Jaffe reaction. We present a case of apparent isolated creatinine elevation after consumption of remote control (RC) fuel, due to interference with the serum creatinine assay. One-year-old and two-year-old male siblings presented to an emergency department after each taking a "swig" of an unknown liquid from a soda can. The mother reported that liquid appeared blue in color and smelled of alcohol while an ED nurse stated it smelled more like acetone. Both children were asymptomatic upon arrival and throughout their emergency department course. Serum electrolytes, including bicarbonate, blood urea nitrogen, and anion gap, were all within normal limits when assayed approximately 90 minutes after ingestion. Serum creatinine determinations for the two siblings were 3.5 mg/dL and 3.8 mg/dL respectively. The product was subsequently identified as Blue Thunder RC racing fuel, containing nitromethane 20% and unspecified methanol. Serum methanol levels were determined to be 10 mg/dL and 12 mg/dL respectively. The patients were discharged with follow-up. Nitromethane may cause isolated dramatic elevations of serum creatinine in the absence of other evidence of nephrotoxicity and acute renal failure. This elevation is artifactual, relates to interference with the complex Jaffe reaction, and requires no further intervention. In analyzing laboratory results, clinicians should interpret unexpected isolated laboratory abnormalities cautiously, especially when not consistent with clinical circumstances and the remainder of the laboratory evaluation.