Which red flag symptoms should prompt immediate referral for a patient presenting with a new-onset headache?

Immediate referral should be considered for a patient presenting with a new-onset headache if any of the following red flag symptoms are present:

• Sudden-onset headache reaching maximum intensity within 5 minutes (thunderclap headache)
• Worsening headache with fever
• New-onset neurological deficit
• New-onset cognitive dysfunction or change in personality
• Impaired level of consciousness
• Recent head trauma (typically within the past 3 months)
• Headache triggered by cough, Valsalva manoeuvre, sneeze, or exercise
• Orthostatic headache (headache that changes with posture)
• Symptoms suggestive of giant cell arteritis
• Symptoms and signs of acute narrow angle glaucoma
• A substantial change in the characteristics of their headache
• Compromised immunity (e.g., HIV or immunosuppressive drugs)
• Age under 20 years with a history of malignancy or a history of malignancy known to metastasise to the brain
• Vomiting without other obvious cause

Additionally, symptoms suggestive of subarachnoid haemorrhage warrant immediate emergency referral, including thunderclap headache, neck pain or stiffness, photophobia, nausea and vomiting, new altered brain function (such as reduced consciousness, seizure, or focal neurological deficit), and limited or painful neck flexion on examination.

Signs suggestive of bacterial meningitis, such as fever, headache, neck stiffness, and altered level of consciousness or cognition, also require urgent hospital transfer.

These red flags indicate potentially serious underlying pathology and necessitate urgent further investigation and specialist assessment.

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