This systematic review aimed to measure the prevalence of inappropriate emergency department (ED) use by adults and associated factors. The review included 31 articles published in the last 12 years. Prevalence of inappropriate ED use varied from 20 to 40% and was associated with age and income. Female patients, those without co-morbidities, without a regular physician, without a regular source of care, and those not referred to the ED by a physician also showed more inappropriate ED use, with the relative risk varying from 1.12 to 2.42. Difficulties in accessing primary health care (difficulties in setting appointments, longer waiting periods, and short business hours at the primary health care service) were also associated with inappropriate ED use. Thus, primary care requires fully qualified patient reception and efficient triage to promptly attend cases that cannot wait. It is also necessary to orient the population on situations in which they should go to the ED and on the disadvantages of consulting the ED when the case is not really urgent.
