Predictors of asthma-chronic obstructive pulmonary disease overlap syndrome in patients with chronic obstructive pulmonary disease from a tertiary care center in India

BACKGROUND: There is dearth of literature on asthma-chronic obstructive pulmonary disease overlap syndrome (ACOS) in India. The aim was to compare clinical characteristics between patients with ACOS and non-ACOS COPD and to identify clinical predictors of ACOS in patients with COPD. METHODS: We conducted a retrospective study by reviewing data collected from patients performing spirometry at our hospital. Those with postbronchodilator FEV(1)/FVC <70% were included in the study. Among them, those with significant reversibility (change in FEV(1) or FVC by 12% and 200 ml postbronchodilator) were diagnosed with ACOS and the rest were considered to have non-ACOS COPD. Data on the 2 groups were compared and statistical analysis was performed. RESULTS: Out of a total of 324 patients, 100 of them had postbronchodilator FEV(1)/FVC <70%. Of them, 45 and 55 were diagnosed with ACOS and non-ACOS COPD, respectively. Patients with ACOS had significantly higher postbronchodilator FVC volumes and FVC % predicted values (P < 0.05), had higher reported wheeze (P = 0.02) and ankle edema (P < 0.05), were more likely to be smokers (P = 0.01) with lower smoking index (P = 0.03), and had frequent (≥2) ER visits (P = 0.04). However, very frequent (≥3 per year) hospital admissions (P < 0.01) with higher rates of invasive mechanical ventilation (P = 0.02), and pulmonary hypertension diagnosed by two-dimensional echocardiography (P < 0.01) were significantly higher in the non-ACOS group. The two groups did not differ with respect to history of atopy, family history of wheeze, compliance to inhaler therapy, or blood absolute eosinophil counts. CONCLUSION: Our study highlights how the ACOS phenotype may clinically differ from their counterparts elsewhere, making it a clinical challenge to identify them in India.