Response time performance for emergency calls has been used as an indicator of ambulance service quality in England since 1974. It was revised in 1996 with targets set of eight minutes for life-threatening (category A) and 19 minutes for urgent (category B) calls. Internationally, response time has been used as the benchmark for emergency medical services (EMS) performance. The evidence to support use of response times as a quality measure has been examined.

A rapid review was used to assess the evidence base for the eight minute response time target. Also, a descriptive observational study of the clinical characteristics of category B calls was performed using two months patient report form data from one English ambulance service.

Five papers were identified that have examined the relationship between response time and mortality for 911/999 emergency call populations. Four papers were from the USA, and in all cases no survival benefit was found for response times > 5 minutes even after adjustment for variables including age, sex and illness severity. This finding was replicated in one UK study. The descriptive study examined call characteristics for 26,882 category B calls. Half of the patients received no intervention other than basic vital signs measurement and 75% had assessment only. Twenty-five percent required some clinical intervention with the majority only requiring oxygen. Less than 5% received significant intervention such as drugs, intravenous cannula, or airway management.

With the exception of cardiac arrest there is consistent evidence that response time has no impact on mortality for EMS calls. Alternative indicators of quality of care should be developed that allow less focus on time targets and more effort on innovation and development of services which could better meet the needs of the majority of patients who do not have a life-threatening problem.