Optimizing Proteinuria Evaluation and Management after Acute Kidney Injury

Key Points. Quantifying albuminuria 3 months after AKI predicts future risk of kidney disease progression but is often not completed. In a cohort of 554 patients with CKD, urine protein-to-creatinine ratio measured within 1 year after AKI had robust prognostic value. Testing of total proteinuria beyond 3 months after AKI among patients with CKD identified those at risk of kidney disease progression. Background. Expert consensus recommends quantifying albuminuria 3 months after hospitalized AKI to identify patients at risk for kidney disease progression, but testing is often not completed in clinical practice. We evaluated the utility of testing total proteinuria (which is less expensive than albuminuria) and on a less rigid time schedule after AKI to facilitate its adoption into clinical practice. Methods. Prospective multicenter cohort study of patients with CKD who were hospitalized with AKI between 2013 and 2021. Urine protein-to-creatinine ratio (PCR) was assessed per research protocol within 1 year of hospital discharge. Cox proportional hazard models were applied with a focus on C-statistics as the primary metric regarding post-AKI PCR's ability to discriminate risk of kidney disease progression as defined by halving of eGFR or ESKD. Results. Five hundred and fifty-four Chronic Renal Insufficiency Cohort participants (43% female, 51% non-Hispanic Black, mean eGFR 43 ml/min per 1.73 m2) had PCR measurements within a year of AKI hospital discharge (82% stage 1 AKI). The median PCR, obtained 147 median (interquartile range, 79-233) days after AKI, was 0.36 mg/g (interquartile range, 0.12–1.37 mg/g). Over the mean follow-up of 2.6 years, 124 participants had kidney disease progression. Higher post-AKI PCR was associated with increased risk of kidney disease progression (hazard ratio, 2.99 for each doubling of proteinuria; 95% confidence interval, 2.54 to 3.52; C-statistic, 0.80). An adjusted model including demographic and clinical risk factors had high discrimination for kidney disease progression (C-statistic, 0.86). Renin-angiotensin system inhibitors use decreased after AKI, especially among patients with higher AKI stage and lower eGFR. Conclusions. Proteinuria evaluation by PCR within 1 year after AKI hospital discharge may be a feasible and flexible option for risk-stratifying survivors at higher risk of subsequent kidney function loss. We also identified opportunities to optimize management of proteinuria after AKI.