Excluding serious illness in feverish children in primary care: restricted rule-out method for diagnosis

Case scenarios

Consider two common scenarios in primary care.

Child 1: A mother calls the out of hours service in the early evening about her 3 year old son. He was seen earlier in the week with cough and runny nose, and the general practitioner (GP) diagnosed an upper respiratory tract infection. He has been getting more miserable and irritable, is lying on the sofa reluctant to move, looks “washed out,” and has a fever. His mother is worried: “Could it be meningitis, doctor?”

Child 2: A 2 year old girl is brought to your morning surgery with a history of a fever that started during the night. You have already seen several children this morning with a non-specific but seemingly mild viral illness.

The diagnostic dilemma

The list of possible diagnoses for febrile children seen in primary care is long. Identifying children who may have a serious illness can be difficult and is at the heart of decisions to prescribe, investigate, and refer to hospital. Serious infections (including pneumonia, meningitis, septicaemia, appendicitis) account for less than 1% of children presenting to primary care,1 2 yet they are leading causes of morbidity and mortality in children. One of the key challenges for primary care practitioners is trying to balance the risk of missing a serious disease against unnecessary investigation or referral. The diagnostic process hinges on the need to rule out (exclude) serious illnesses.

The diagnostic approach: the restricted rule-out

Many doctors come to use some variant of the restricted rule-out method, which recognises that we cannot rule out all of the alternative diagnoses for each presenting complaint, but that there is a short list of serious ones …