# Urine Albumin-Creatinine Ratio (ACR) of Patients With Chronic Obstructive Pulmonary Disease (COPD): A Cross-Sectional Study

## TL;DR

This study found that COPD patients have higher urine albumin-creatinine ratios, which are linked to disease severity and age-related lung function decline.

## Contribution

The study explores the relationship between urine ACR and COPD severity markers like GOLD stage and CAT score for the first time in this population.

## Key findings

- Urine ACR was positively correlated with COPD severity (GOLD stage and CAT score).
- FEV1 decreased with age and was negatively associated with urine ACR.
- Most COPD patients had mild to moderate disease (GOLD stages 2 and 3).

## Abstract

Background and objectives

Chronic obstructive pulmonary disease (COPD) and chronic kidney disease (CKD) may coexist. Their co-occurrence and impacts on renal and pulmonary functions have not been explored in detail. We planned this study to evaluate urine albumin-creatinine ratio (ACR) levels among patients with COPD. We also assessed the correlation among age, urine ACR, forced expiratory volume in 1 second (FEV1), Global Initiative for Chronic Obstructive Lung Disease (GOLD) stage, and COPD Assessment Test (CAT) score of the participants.

Methods

This cross-sectional study was conducted at Kalinga Institute of Medical Sciences (KIMS), Bhubaneswar, India, from March 2023 to April 2025. The following parameters were noted from the case sheets after admission: age, serum creatinine, urine albumin, urine creatinine, urine ACR, FEV1, forced vital capacity (FVC), FEV1/FVC, GOLD stage, and CAT score. We correlated all these values. We used R software (version 4.4.3; R Foundation for Statistical Computing, Vienna, Austria) for data analysis.

Results

Three hundred fifty-seven patients were recruited for the study. The median age of the participants was 61.0 years (54.0-69.0 years). 233 (65.3%) participants were males. The median serum creatinine was 1.97 mg/dL (0.81-2.48 mg/dL). The study population's median urine ACR was 24.59 mg/g (10.83-50.13 mg/g). The median FEV1 was 46.79% (39.78-60.72%) of the predicted value. The median FEV1/FVC was 0.57 (0.53-0.60). According to the GOLD staging, most individuals fell into stages 2 (134, 37.5%) and 3 (156, 43.7%). The median CAT score was 18.0 (14.0-21.0). There were positive associations between GOLD stage and CAT score (r = 0.767, p < 0.001), age and GOLD stage (r = 0.673, p < 0.001), and age and CAT score (r = 0.622, p < 0.001). There were negative associations between GOLD stage and FEV1 (r = -0.945, p < 0.001), age and FEV1/FVC (r = -0.851, p < 0.001), FEV1 and CAT score (r = -0.755, p < 0.001), and age and FEV1 (r = -0.736, p < 0.001). The significant correlations with urine ACR were found with GOLD stage (r = 0.409, p < 0.001), CAT score (r = 0.310, p < 0.001), FEV1 (r = -0.357, p < 0.001), and FEV1/FVC (r = -0.229, p < 0.001).

Conclusion

Urine ACR and CAT scores were higher among the elderly population. With aging, FEV1 readings decreased. Our study showed weak correlations between the lung parameters and urine ACR.