Patient with severe burns for whom serum cystatin C-based assessment was performed due to suspected errors in serum creatinine-based renal function evaluation: a case report.

A 68-year-old male with severe burns was admitted for treatment. During the prolonged hospitalisation, discrepancies were observed between estimated glomerular filtration rate (eGFR) based on serum creatinine (eGFRcre) and actual renal function, as indicated by vancomycin therapeutic drug monitoring. Serum cystatin C measurement revealed a difference between eGFR based on serum cystatin C (eGFRcys) and eGFRcre. The patient experienced drug-induced liver injury, likely due to an inaccurate renal function assessment using serum creatinine. Adjusting drug doses based on eGFRcys improved clinical outcomes. Therefore, eGFRcre may overestimate renal function in patients with decreased muscle mass from prolonged hospitalisation and reduced physical activity. In emergency medicine, especially for patients with conditions affecting muscle mass, eGFRcys may be a more reliable marker for renal function evaluation than eGFRcre. Hence, alternative methods should be considered for assessing renal function in special populations to ensure appropriate drug dosing and prevent adverse effects.