Letter to the editor: "Urine albumin-to-creatinine ratio for early diagnosis and risk stratification of acute kidney injury in high-risk critically ill ICU patients: A prospective cohort study".

We read with great interest the article by Kitisin et al. published in the Journal of Critical Care. In our letter, we focus on raising a key methodological concern: when "persistent AKI" is defined as "lasting more than 48 hours from AKI onset," and serum creatinine and urine output are only specified as "at least twice daily" assessments, the heterogeneity in monitoring intensity among different patients may influence outcome determination. Variable sampling frequencies (potentially related to disease severity or influenced by clinicians' awareness of uACR results) alter the capture of AKI onset and recovery time points, leading to outcome misclassification near the 48-h threshold and potentially weakening (underestimating) the true association between uACR and persistent AKI in the present study.