What criteria should I use to decide when to refer a patient with PUO to secondary care for further evaluation?

Criteria for referral of a patient with pyrexia of unknown origin to secondary care include:

• Presence of any 'red' features indicating serious illness or immediately life-threatening conditions, which require urgent referral to a paediatric specialist or emergency care within 2 hours ¹.
• Presence of 'amber' features without a clear diagnosis, where clinical judgement should guide the urgency of referral or arranging further assessment by a paediatric specialist ¹.
• Infants younger than 3 months with fever should be referred for observation and investigations including full blood count, blood culture, C-reactive protein, urine testing, and possibly lumbar puncture, especially if they appear unwell or have abnormal white blood cell counts ¹.
• Children with fever who are shocked, unrousable, or showing signs of meningococcal disease require urgent review by a paediatrician and consideration for intensive care referral ¹.
• If no diagnosis is reached but the child remains ill longer than expected for a self-limiting illness, or if social/family circumstances or parental anxiety are significant, referral or close follow-up should be considered ¹.
• Children with fever without apparent source but with 'red' or 'amber' features should have investigations performed and be referred for specialist assessment ¹.
• Children with 'green' features and no amber or red features can be managed at home with safety netting advice, so referral is not routinely required unless clinical condition changes ¹.