We report a case of a 25-year-old man with a falsely elevated serum creatinine level caused by a commonly used hospital medication. The patient presented to the hospital with necrotising soft tissue infection of his left index finger. Wound culture grew Streptococcus pyogenes , and antibiotic treatment was started. Initial laboratory data showed: CRP 273 mg/L, creatinine 105 μmol/L (eGFR 85 mL/min/1.73 m 2 ), urea 5.8 mmol/L. Creatinine was measured enzymatically on the Roche analyser. On day 6 of admission, the patient’s creatinine level suddenly increased to 214 μmol/L (a 243% rise within 2 hours). This discrepancy from the clinical presentation suggested a spurious or non-renal cause. Repeat testing with a different method produced a similar result (217 μmol/L, Jaffe method). Further investigation showed that the patient had received 4 mg/mL of intravenous dexamethasone about 5 minutes before the blood sample was taken. The lab requested a repeat sample, which reported a creatinine level of 78 μmol/L. To investigate further, we obtained dexamethasone sodium phosphate and found it contained an extremely high creatinine level (44,700 μmol/L). Our findings confirm that falsely high creatinine results can occur due to sample contamination with certain brands of intravenous dexamethasone. Some, but not all, preparations of intravenous dexamethasone contain creatinine as an excipient to improve stability, act as a buffering agent, or reduce viscosity. This case broadens our understanding and underscores the importance of recognising pre-analytical factors and raising awareness of pharmacologically induced results that are inconsistent with the clinical picture.
Suthaharen et al. (Sun,) studied this question.