Impact of Chronic Kidney Disease Severity on COVID-19 Outcomes: A Retrospective Cohort Study

Background/Objectives: Chronic kidney disease (CKD) is a recognised risk factor for severe COVID-19, but comparative outcomes between conservatively managed CKD patients and those on maintenance haemodialysis (HD) remain incompletely characterised, particularly in Central Asia. This study evaluated the impact of CKD severity on clinical outcomes, inflammatory profiles, and mortality in hospitalised COVID-19 patients. Methods: This retrospective cohort study reviewed 891 patients hospitalised with COVID-19 at a tertiary infectious disease centre in Almaty, Kazakhstan, between 2020 and 2021. Patients were stratified into three groups: No CKD (n = 598), CKD without HD (n = 116), and CKD on maintenance HD (n = 177). Demographic, laboratory, treatment, and outcome data were extracted from electronic medical records. Multivariate logistic regression was used to identify independent predictors of in-hospital mortality, acute kidney injury (AKI), and intensive care unit (ICU) admission. Model 1 served as the primary prognostic model, while Model 2 explored in-hospital complications. Results: Patients with CKD exhibited significantly higher inflammatory markers, with peak C-reactive protein reaching 168.3 mg/L in the HD group compared to 44.4 mg/L in the No CKD group. In-hospital mortality was highest in the CKD without HD group (34.8%), followed by CKD on HD (21.7%) and No CKD (13.6%). AKI occurred in 35.7% of conservatively managed CKD patients. In multivariate analysis, CKD without HD independently predicted mortality (OR 3.23; 95% CI 1.38–7.63) and AKI (OR 4.12; 95% CI 1.73–10.03). Conversely, established HD status was not a significant independent predictor of mortality after adjusting for age and comorbidities. Conclusions: CKD severity strongly influences COVID-19 prognosis. Paradoxically, conservatively managed CKD patients carry a higher mortality and AKI risk than patients already on maintenance HD, which may be associated with the absence of scheduled volume and metabolic control, although causal inferences cannot be drawn from this observational data. These findings support the need for aggressive monitoring and early nephrological intervention in non-dialysis CKD patients hospitalised with severe viral respiratory infections.