Which initial investigations should be performed to confirm the presence of a pleural effusion in primary care?

Initial investigations in primary care to confirm the presence of a pleural effusion include:

• Clinical examination focusing on chest signs such as reduced chest expansion, stony dull percussion note, and decreased or absent breath sounds on the affected side, which are typical findings suggestive of pleural effusion.
• Chest radiography (chest X-ray) to assess for pleural effusion and underlying lung pathology; this is the key imaging investigation recommended in primary care.
• Pulse oximetry to assess oxygen saturation, if available, as hypoxia may be present.
• Full blood count to exclude anaemia or other hematological abnormalities that may contribute to symptoms.
• Ultrasonography of the chest can be used to exclude or confirm pleural effusion, though it may be more commonly performed in secondary care or specialist settings.

Further investigations such as computed tomography (CT) of the chest may be required in secondary care for detailed assessment or if malignancy or tuberculosis is suspected.

These recommendations are based on clinical assessment and the NICE Clinical Knowledge Summaries (CKS) guidelines on dyspnoea, breathlessness, and suspected cancer recognition and referral pathways ¹,³,⁴.