How do you know if your child's infection is serious?

In the commentary on a study just published in the prestigious medical journal The Lancet, the author states:

"In developed countries, every child will present to a primary health-care practitioner more than once every year with symptoms of an acute infection. Primary care physicians faced with such a child know that the likelihood of serious disease is about 1%, but what has not been clear is the evidence-based approach that clinicians should take in investigating such children. In The Lancet today, Ann Van den Bruel and colleagues address this uncertainty..."

In other words, if your child has an acute infection, there is a 99% chance that it is not serious. But to catch the 1% that need a more aggressive intervention, the study identified these red flags:

"Cyanosis [bluish discoloration of skin, mucous membranes, nail beds, etc.], rapid breathing, poor peripheral perfusion [poor delivery of arterial blood to the capillaries—check the nail beds], and petechial rash were identified as red flags in several studies. Parental concern and clinician instinct were identified as strong red flags in one primary care study. Temperature of 40°C [104°F] or more has value as a red flag in settings with a low prevalence of serious infection. No single clinical feature has rule-out value but some combinations can be used to exclude the possibility of serious infection—for example, pneumonia is very unlikely if the child is not short of breath and there is no parental concern."

Though this is not a fool-proof checklist, it is still worth bearing in mind:

1. Cyanosis (bluish discoloration)
2. Rapid breathing
3. Poor perfusion of blood in the extremities
4. Petechial rash (red-purple spots 1-2 mm in diameter)
5. Your instinct that something is seriously wrong
6. Persistent fever over 104°F (particularly with the above; remember that fever is a necessary part of the immune response).