Missed diagnoses in general practice are inevitable. No diagnostic test or clinical decision rule in general practice is 100% sensitive. This is largely because individuals, both children and adults, present at different stages in the evolution of their illness. At an early stage classic ‘red-flag’ features of serious illness may be absent; for example, half the cases of meningococcal disease in children are missed by GPs at first presentation often because the characteristic features of the illness are yet to appear.1 Similarly at first presentation, the serious complications of an usually uncomplicated illness may not have developed; for example, dehydration in gastroenteritis or sub-dural haematoma after head injury. Safety-netting is a diagnostic strategy to deal with this situation. The term ‘safety-netting’ was introduced to general practice by Roger Neighbour who considered it a core component of the general practice consultation.2 He defined safety-netting as encompassing three questions:
- If I'm right what do I expect to happen?
- How will I know if I'm wrong?
- What would I do then?
However, the evidence-base is scanty and even a brief discussion with clinical colleagues will confirm that there is little agreement on how to interpret and apply diagnostic safety-netting in practice.