Assessment of Acute Kidney Injury and Longitudinal Kidney Function After Hospital Discharge Among Patients With and Without COVID-19

IMPORTANCE: Acute kidney injury (AKI) occurs in up to half of patients hospitalized with coronavirus disease 2019 (COVID-19). The longitudinal effects of COVID-19–associated AKI on kidney function remain unknown. OBJECTIVE: To compare the rate of change in estimated glomerular filtration rate (eGFR) after hospital discharge between patients with and without COVID-19 who experienced in-hospital AKI. DESIGN, SETTING, AND PARTICIPANTS: A retrospective cohort study was conducted at 5 hospitals in Connecticut and Rhode Island from March 10 to August 31, 2020. Patients who were tested for COVID-19 and developed AKI were screened, and those who survived past discharge, did not require dialysis within 3 days of discharge, and had at least 1 outpatient creatinine level measurement following discharge were included. EXPOSURES: Diagnosis of COVID-19. MAIN OUTCOMES AND MEASURES: Mixed-effects models were used to assess the association between COVID-19–associated AKI and eGFR slope after discharge. The secondary outcome was the time to AKI recovery for the subgroup of patients whose kidney function had not returned to the baseline level by discharge. RESULTS: A total of 182 patients with COVID-19–associated AKI and 1430 patients with AKI not associated with COVID-19 were included. The population included 813 women (50.4%); median age was 69.7 years (interquartile range, 58.9-78.9 years). Patients with COVID-19–associated AKI were more likely to be Black (73 [40.1%] vs 225 [15.7%]) or Hispanic (40 [22%] vs 126 [8.8%]) and had fewer comorbidities than those without COVID-19 but similar rates of preexisting chronic kidney disease and hypertension. Patients with COVID-19–associated AKI had a greater decrease in eGFR in the unadjusted model (−11.3; 95% CI, –22.1 to −0.4 mL/min/1.73 m(2)/y; P = .04) and after adjusting for baseline comorbidities (−12.4; 95% CI, –23.7 to −1.2 mL/min/1.73 m(2)/y; P = .03). In the fully adjusted model controlling for comorbidities, peak creatinine level, and in-hospital dialysis requirement, the eGFR slope difference persisted (−14.0; 95% CI, –25.1 to −2.9 mL/min/1.73 m(2)/y; P = .01). In the subgroup of patients who had not achieved AKI recovery by discharge (n = 319), COVID-19–associated AKI was associated with decreased kidney recovery during outpatient follow-up (adjusted hazard ratio, 0.57; 95% CI, 0.35-0.92). CONCLUSIONS AND RELEVANCE: In this cohort study of US patients who experienced in-hospital AKI, COVID-19–associated AKI was associated with a greater rate of eGFR decrease after discharge compared with AKI in patients without COVID-19, independent of underlying comorbidities or AKI severity. This eGFR trajectory may reinforce the importance of monitoring kidney function after AKI and studying interventions to limit kidney disease after COVID-19–associated AKI.