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Mr Thakore and colleagues (March 2002 JRSM1) conclude that 55% of calls for emergency ambulances did not merit an immediate response. As they acknowledge, the design of the study was not ideal. The initial reason for the request was determined from ambulance crew and accident and emergency (A&E) data after the patient had been seen. This will almost inevitably introduce bias when applying the triage criteria, and the assessment should have been blinded. Also, it is much easier to make such determinations in hindsight, with additional time and clinical information, than when faced with a real call when one has to consider the consequences of the decision reached.
It is surprising that this paper makes no reference to priority-based dispatch systems, such as the Advanced Medical Priority Dispatch System (AMPDS), as these are currently used by most ambulance services in the UK. These systems have been shown to have a low risk of serious under-prioritization of life-threatening episodes2. However, work that we have undertaken in Nottingham suggests that they may not be very effective in predicting low-priority 999 calls3.
The NHS Executive has stressed the importance of developing telephone prioritization systems that will free ambulance services from having to respond to ‘patients who dialled 999 but who do not need emergency care’4. We believe this may be difficult to achieve. Appropriate and effective telephone triage on non-emergency 999 calls requires a greater understanding of the relationship between the initial telephone assessment by ambulance control and the subsequent outcome of the individual call. Without these data we will not be able to ensure that such a system could operate safely and we endorse the authors' views that prospective studies are essential to assess the feasibility of accurately identifying lower priority calls.