TF and acute kidney injury: In the present study, the urinary NAG levels in the SMPP group were significantly higher than those in the non-SMPP group, and the AKI group had higher urinary NAG, α1-microglobulin, β2-microglobulin, urinary microalbumin, urinary transferrin and retinol-binding protein levels than the non-AKI group, with NAG levels being the most likely marker to be elevated.