Variation in inpatient investigations and treatment practices for COPD exacerbations between respiratory and internal medicine specialties: a retrospective cohort study

Introduction Chronic obstructive pulmonary disease (COPD) exacerbations are a major cause of hospitalization and healthcare utilization. The impact of inpatient specialty allocation on management practices remains unclear. This study examined variation in investigations and treatment practices among COPD patients admitted under respiratory medicine (RM) compared with internal medicine (IM), and evaluated clinical characteristics associated with RM admission. Methods We conducted a retrospective cohort study of adults aged ≥40 years admitted for COPD exacerbations between January 2017 and March 2025. Patients were identified using ICD-10 COPD codes, excluding those admitted directly to ICUs or with asthma or bronchiectasis. Demographics, comorbidities, investigations, treatments, and hospitalization outcomes were analyzed. The primary outcome was variation in investigations and treatment practices between RM and IM admissions. The secondary outcome was identification of clinical characteristics associated with RM admission using multivariable logistic regression. Results Among 6,277 COPD admissions, 3,211 (51.2%) were under RM and 3,066 (48.8%) under IM. Patients admitted under RM were younger (73.2 ± 10.7 vs. 75.6 ± 10.8 years, p  < 0.001) and had fewer comorbidities, including ischemic heart disease (IHD), diabetes (DM), stroke, and chronic kidney disease (CKD). RM admissions underwent more respiratory-focused investigations, including chest radiography (54.2% vs. 43.5%), chest CT (8.4% vs. 5.6%), and ABG testing (23.1% vs. 8.2%). Non-invasive ventilation (17.7% vs. 4.2%) and invasive mechanical ventilation (18.2% vs. 4.3%) were more frequently used in RM admissions. Use of intravenous antibiotics, routine laboratory testing, allied health involvement, and palliative care services were more frequent in IM admissions. Descriptive differences in hospital outcomes were also observed, with RM admissions demonstrating lower in-hospital mortality (3.9% vs. 6.5%, p  < 0.001) and shorter hospitalization duration (5.85 vs. 6.93 days, p  < 0.001), while 30-day readmissions were similar. In multivariable analysis, older age (OR 0.97, 95% CI 0.96–0.99), male sex (OR 0.49), IHD (OR 1.60), stroke (OR 1.70), and CKD (OR 1.94 were associated with RM admission). Conclusion Variation in investigations and treatment practices was observed between RM and IM admissions for COPD exacerbations. These differences likely reflect variation in patient characteristics, illness severity, and clinical workflows rather than differences in quality of care attributable to specialty alone.