# Early Changes in Renal Function as Predictors of In-Hospital Mortality in COVID-19 Patients

## TL;DR

This study shows that early changes in kidney function within the first 48 hours of hospitalization for COVID-19 can predict in-hospital mortality better than static kidney measures.

## Contribution

The study introduces a novel approach using dynamic early kidney function patterns to improve risk stratification in hospitalized COVID-19 patients.

## Key findings

- Early improvement in kidney function was associated with higher in-hospital mortality compared to stable function.
- Early deterioration in kidney function showed a similar trend but was not statistically significant.
- Early improvement was linked to higher AKI burden and increased need for hemodialysis.

## Abstract

Background: Acute kidney injury (AKI) is a frequent and prognostically relevant complication of COVID-19. However, reliance on static creatinine values or binary AKI definitions may overlook clinically meaningful early renal dynamics. We evaluated whether early renal function trajectories within the first 24–48 h of hospitalization provide incremental prognostic information. Methods: We conducted a retrospective, single-center cohort study of adults hospitalized with laboratory-confirmed COVID-19 between December 2020 and December 2021. Early renal function patterns were defined using KDIGO-based changes in serum creatinine between admission and 24–48 h, classifying patients as stable, early improvement, or early deterioration. The primary outcome was in-hospital mortality. Multivariable logistic regression adjusted for age, sex, chronic kidney disease, comorbidities, inflammatory burden (C-reactive protein), nutritional status (albumin), pulmonary involvement, and treatment variables. Results: Among 721 patients, 65.2% had stable renal function, 22.5% had early improvement, and 12.3% had early deterioration. In-hospital mortality differed significantly across dynamic patterns (p = 0.007). Mortality was lowest in the stable group (35.1%) and higher in both early improvement (48.1%) and early deterioration (44.9%). After multivariable adjustment, early improvement remained independently associated with higher in-hospital mortality compared with stable renal function (adjusted OR 1.53, 95% CI 1.03–2.28), while early deterioration showed a directionally similar but non-significant association. Early improvement was also associated with higher AKI burden and increased need for acute de novo hemodialysis. Conclusions: Early renal function change patterns within the first 24–48 h of hospitalization carry prognostic value beyond static creatinine measures. Apparent early creatinine improvement may reflect recovery from prior injury or systemic instability rather than true renal recovery, identifying a subgroup at heightened risk. Classification based on early renal function assessment may enhance early risk stratification in hospitalized patients with COVID-19.