Diagnostic safety-netting.

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 subdural 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: 1. If I'm right what do I expect to happen? 2. How will I know if I'm wrong? 3. 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. Ruling-out serious illness often takes precedent over ruling in a particular illness in both general practice and emergency departments. 3 Up to 50% of patients will not have a firm diagnosis at the end of a consultation with their GP and yet the need to rule out serious illness remains. 4 Safety-netting is critically important in this situation. It is also critically important if the diagnosis is known but carries a significant risk of serious complications either in itself (for example, dehydration in gastroenteritis) or because the individual characteristics of the patient put them at particularly high risk of complications (for example, they have significant comorbidity or are having treatment which reduces their immune system). Box 1 summarises the three high-risk clinical situations where effective safety-netting is mandatory. There is some published data on the second category; for example, surveys of the safety-net advice given to people discharged after head injury from emergency departments 5,6 and trials of the effectiveness of different methods of follow-up of patients with asthma. 7 In both cases the evidence highlights the range of methods employed without providing much help about how and what safety-net advice should be given. In the absence …