# Association between the C-reactive protein to albumin ratio and unplanned readmission in ulcerative colitis: insights from a cohort study

## TL;DR

This study found that higher C-reactive protein to albumin ratio (CAR) is linked to more unplanned hospital readmissions in ulcerative colitis patients, suggesting CAR could help predict readmission risk.

## Contribution

The study introduces CAR as a novel predictive biomarker for unplanned readmissions in ulcerative colitis patients.

## Key findings

- Each 1-unit increase in CAR was associated with a 126.9% higher risk of unplanned readmission.
- CAR showed good predictive performance across multiple follow-up periods with AUC values above 0.77.
- A non-linear relationship and threshold effect were identified between CAR and readmission risk.

## Abstract

This study aimed to investigate the association between the C-reactive protein to albumin ratio (CAR) and unplanned readmissions in patients with ulcerative colitis (UC) and to evaluate its potential value as a predictive indicator.

This study included 412 patients with UC who were hospitalized at the Affiliated Hospital of Shandong University of Traditional Chinese Medicine between June 2017 and June 2024. Cox proportional hazards models were used to evaluate the relationship between CAR, C-reactive protein (CRP), albumin (ALB), and unplanned readmission in patients with UC. Kaplan-Meier survival curves were plotted to analyze the differences in unplanned readmission rates across different value ranges. Restricted Cubic Splines (RCS) were employed to explore the dose-response relationship between these three variables and unplanned readmissions. Additionally, a subgroup analysis was conducted to evaluate the applicability of the model across different populations. The predictive performance of CAR was assessed using Receiver Operating Characteristic analysis.

During the 1-year follow-up, the unplanned readmission rate among patients with UC was 27.43%. After adjusting for potential confounders, each 1-unit increase in CAR was associated with a 126.9% higher risk of unplanned readmission. Kaplan-Meier survival curves demonstrated significant differences in unplanned readmission rates among UC patients stratified by CAR, CRP, and ALB quartiles (log-rank test, P < 0.001). The RCS curves revealed a positive correlation (P for overall < 0.001) and a non-linear relationship (P for non-linear < 0.001) between CAR and unplanned readmission rates in patients with UC. Threshold effect analysis identified an inflection point for unplanned readmissions in the regression model (W = 0.654). Subgroup analysis suggested a potential interaction between hypertension and CAR in relation to unplanned readmission in patients with UC. Finally, the CAR demonstrated good predictive performance at the 1-month, 3-month, 6-month, and 1-year follow-up periods, with the area under the receiver operating characteristic curve values of 0.813, 0.779, 0.778, and 0.799, respectively.

Elevated CAR levels were significantly correlated with increased rates of unplanned readmissions, suggesting its potential as an independent prognostic indicator for patients with UC.