Microalbuminuria as a Marker of Chronic Obstructive Pulmonary Disease Severity: Association with GOLD Stage, Dyspnea and CAT Score

Abstract Background Chronic obstructive pulmonary disease (COPD) has important systemic manifestations in addition to persistent airflow limitation. Microalbuminuria, assessed using the urinary albumin-to-creatinine ratio (UACR), may reflect generalized endothelial and microvascular dysfunction. This study evaluated the association of microalbuminuria with COPD severity assessed by GOLD spirometric stage, Modified Medical Research Council (mMRC) dyspnea grade and COPD Assessment Test (CAT) score. Methods A prospective observational study was conducted from March 2024 to March 2026 in the Department of Respiratory Medicine, Ramaiah Medical College and Hospital, Bengaluru. Adults with COPD diagnosed according to GOLD criteria, a documented CAT score and at least 10 smoking pack-years were enrolled. Patients with heart failure, chronic kidney disease, liver cirrhosis, ischemic heart disease, HIV infection or urinary tract infection were excluded, as were pregnant or menstruating participants at urine collection. Clinical assessment, post-bronchodilator spirometry, CAT scoring and a single midstream morning UACR measurement were performed. Associations were evaluated using chi-square/Fisher exact tests, independent-samples t-test, Pearson correlation and ANOVA as applicable. Results Among 166 participants, the mean age was 62.48 ± 7.83 years and 65.7% were men. Mean FEV1 was 1.45 ± 0.71 L and mean FEV1% predicted was 51.33 ± 22.42%. Microalbuminuria was present in 82 participants (49.4%), with a mean UACR of 85.77 ± 81.26 mg/g. Its prevalence increased from 16.7% in GOLD stage I to 33.3% in stage II, 62.5% in stage III and 78.1% in stage IV (p < 0.001). Prevalence also increased across mMRC grades, from 22.2% in grade 0 and 20.0% in grade 1 to 51.5%, 64.3% and 85.7% in grades 2, 3 and 4, respectively (p < 0.001). Participants with microalbuminuria had higher mean CAT scores than those without microalbuminuria (27.23 ± 9.31 vs 18.75 ± 9.05; p < 0.001). UACR showed a strong positive correlation with CAT score (r = 0.655, p < 0.001). Conclusion Microalbuminuria was common in this COPD cohort and was strongly associated with increasing airflow limitation, dyspnea and symptom burden. UACR may have potential as a simple, non-invasive marker of systemic involvement and disease severity in COPD. Larger longitudinal studies with repeated UACR measurements and adjustment for vascular and metabolic confounders are required before routine clinical use can be recommended.