Diagnosis of an exacerbation is usually made clinically. In patients who have their exacerbation managed in primary care: (1,2)
- sending sputum samples for culture is not recommended in routine practice
 - pulse oximetry is of value if there are clinical features of a severe exacerbation
 
In all patients with an exacerbation referred to hospital
- a chest radiograph should be obtained
 - arterial blood gas tensions should be measured and the inspired oxygen concentration should be recorded
 - an ECG should be recorded (to exclude comorbidities)
 - a full blood count should be performed and urea and electrolyte concentrations should be measured
 - measure theophylline level on admission in people who are taking theophylline therapy
 - if sputum is purulent, a sample should be sent for microscopy and culture
 - blood cultures should be taken if the patient has pyrexia (1)
 
Reference:
- National Institute for Health and Care Excellence. Chronic obstructive pulmonary disease in over 16s: diagnosis and management. Jul 2019 [internet publication].
 - Global Initiative for Chronic Obstructive Lung Disease (GOLD). Global strategy for the diagnosis, management, and prevention of chronic obstructive pulmonary disease: 2025 report. 2025 [internet publication].