# The prognostic value of admission serum uric acid for acute kidney injury: a two-center retrospective analysis

## TL;DR

This study finds that both very low and very high admission serum uric acid levels are linked to a higher risk of acute kidney injury, with kidney function affecting this relationship.

## Contribution

The study identifies a U-shaped relationship between serum uric acid and AKI risk and highlights the modifying role of kidney function.

## Key findings

- A U-shaped association was found between serum uric acid and AKI risk.
- Both very low and very high SUA levels increased AKI risk, though the effect was stronger at lower levels.
- Kidney function modified the strength of the SUA-AKI relationship, with weaker associations in patients with poor kidney function.

## Abstract

Acute kidney injury (AKI) is a serious clinical syndrome, with elevated serum uric acid (SUA) recognized as a potential modifiable risk factor. Nonetheless, the association between reduced SUA and the risk of AKI, along with the modification by kidney function on this association, is not well understood.

All adult patients from Peking University First Hospital (PKUFH) were screened. The primary outcome was AKI during hospitalization. Restricted cubic spline (RCS) was utilized to examine the hypothesized non-linearity between AKI and SUA as a continuous variable. SUA was categorized into six groups and Poisson regression was applied to evaluate the association between SUA groups and AKI with 240–360 μmol/L as reference. Subgroup analysis was conducted in terms of estimated glomerular filtration rate (eGFR).

Among 62,775 patients enrolled from PKUFH, 1,866 patients developed AKI (3.0%). The RCS plot showed a U-shaped association between SUA and AKI. Compared with reference group, SUA ≤ 180 μmol/L and >480 μmol/L exhibited a 2.17-fold and a 4.86-fold increased risk of AKI in the unadjusted model. After full adjustment, the associated risk of AKI in SUA ≤ 180 μmol/L (RR 1.92, 95% CI 1.57–2.36) and SUA > 480 μmol/L (RR 1.17, 95% CI 1.03–1.34) was weakened but still demonstrated statistical significance. When stratified by eGFR, the U-shaped risk curve was much less steep in the subgroup with eGFR ≤ 45 mL/min/1.73 m2.

This study reveals a U-shaped association between admission SUA and AKI risk. Kidney function is an important confounder for this association.