Estimated glomerular filtration rate in post COVID-19 patients at 3–6 months and 12–18 months after infection

Background: Some degree of renal impairment is common during acute COVID-19 infection. However, it remains unclear whether this impairment is temporary or persists long term. In this study we compare kidney function (via estimated glomerular filtration rate [eGFR]) during infection, 3–6 months and 12–18 months after infection; the relationship between patient characteristics and eGFR in post COVID-19 patients; and the difference in eGFR between post COVID-19 patients and controls. Methods: In total, 95 post COVID-19 patients and 94 controls were included. Post COVID-19 patients were seen 3–6 months and 12–18 months after infection for biological sample collection and questionnaire administration, with results for biological samples during acute infection sourced from medical records. Mixed model analyses were performed to study the associations between patient characteristics and eGFR and linear regression analyses to study the difference between post COVID-19 patients and controls. Results: Under a complete case analysis among post COVID-19 patients (where results available at the acute phase and both follow-up points, n = 61), the eGFR was <90 mL/min/1.73 m² in 50.8% during infection, in 68.9% at visit 1 and in 75.4% at visit 2, compared with 40.4% in the control group. The eGFR was lower among patients with a higher age, those who had been hospitalized, and those with CVD/hypertension. After adjusting for confounders, the eGFR at the 12–18 month time point was significantly lower in post COVID-19 patients than controls. Conclusions: Previous COVID-19 infection was associated with a reduced eGFR up to 18 months after infection with higher age and CVD/hypertension increasing this likelihood.