Differentiating True Nephrotoxicity From Pseudo-nephrotoxicity: A Prospective Comparative Study of Vancomycin Plus Piperacillin-Tazobactam vs. Meropenem Using Serum Creatinine and Cystatin-C

This prospective comparative observational study will compare the incidence of true nephrotoxicity in adult patients receiving vancomycin in combination with either piperacillin-tazobactam or meropenem. Vancomycin plus piperacillin-tazobactam has been associated with a higher incidence of kidney injury based mainly on increases in serum creatinine. However, it remains uncertain whether these increases represent true kidney injury or pseudo-nephrotoxicity, in which serum creatinine increases without a corresponding decline in kidney function. To address this uncertainty, the study will prospectively assess kidney function using both serum creatinine and cystatin C. True nephrotoxicity will be identified when changes in both biomarkers meet the study criteria for acute kidney injury, while an increase in serum creatinine without a corresponding cystatin C increase will be considered pseudo-nephrotoxicity. The study will compare true nephrotoxicity between patients receiving vancomycin plus piperacillin-tazobactam and those receiving vancomycin plus meropenem. It will also evaluate the timing, persistence, severity, and recovery of kidney injury. The results may help clarify whether the higher rates of nephrotoxicity reported with vancomycin plus piperacillin-tazobactam represent true renal injury and may help guide antibiotic selection when balancing antimicrobial coverage and kidney safety.