CRP and susceptibility to pneumonia measurement: The variables entered into the model included age, sex, smoking status, disease severity classification (GOLD stage), comorbidities (cardiovascular diseases, osteoporosis, active cancer, asthma overlapping, pneumonia, diabetes, metabolic disease), vital signs (indication for oxygen supplementation, respiratory insufficiency), laboratory values (CRP, leukocytosis, eosinophiles), and admission urgency (ambulance transportation).