Multiple studies showed elevated NGAL concentrations in patients without serum creatinine concentration-based AKI, likely identifying patients with suspected AKI stage 1S (subclinical AKI).<h4>Limitations</h4>Imperfect harmonization of data across studies because of their original protocols.<h4>Conclusions</h4>NGAL concentration differences may facilitate identification of patients at risk of AKI or with suspected AKI stage 1S at admission. Here, LCN2 is linked to acute kidney injury.