Long-term effects of COVID-19 on kidney function

Chaolin Huang and colleagues¹ have highlighted the putative renal consequences of COVID-19 at 6 months from discharge. A decreased estimated glomerular filtration rate (eGFR) was defined as less than 90 mL/min per 1·73 m² and was observed in 35% of participants during follow-up. The term decreased eGFR is ambiguous. According to the mean age of the cohort, chronic kidney disease should be defined as an eGFR of less than 60 mL/min per 1·73 m².² The usual prevalence of eGFR less than 90 mL/min per 1·73 m² in the Chinese general population of similar ages to those in Huang and colleagues' cohort ranges between 35% and 50%.3, 4 In other words, the prevalence of eGFR of less than 90 mL/min per 1·73 m² in COVID-19 survivors might not differ from the general population. Furthermore, the majority of patients with eGFR less than 90 mL/min per 1·73 m² during follow-up did not show acute kidney injury during the acute phase, which suggests that the eGFR of these patients was already less than 90 mL/min per 1·73 m² before COVID-19. Therefore, the prevalence of patients with eGFR less than 60 mL/min per 1·73 m² at 6 months from discharge is required to factually assess the long-term effect of COVID-19 on renal function. The pathological relevance of an eGFR between 60 and 90 mL/min per 1·73 m² is questionable in the absence of proteinuria.² Proteinuria has been frequently described in patients with COVID-19. Our follow-up observations suggest a spontaneous remission within a few weeks after discharge.⁵ The available data of Huang and colleagues do not support their alarming conclusions about the poor renal prognosis at 6 months after COVID-19.