Hospital activity and cost incurred because of unregistered patients in England: considerations for current and new commissioners.

Background: Commissioners are responsible for providing health care for defined geographical areas. A lack of comprehensive national and local information on health needs of unregistered populations makes health service planning difficult.

Methods: A cross-sectional study using Hospital Episode Statistics to quantify the level of inpatient and outpatient activity, and associated cost by patients not registered in primary care in English NHS hospitals. Unregistered patients were defined as those without a valid GP registration, prisoners, military personnel, asylum seekers/immigrants and the homeless.

Results: Unregistered patients accounted for 99 615 inpatient admissions and 370 504 outpatient attendances in 2009/10, at a total cost of £242 m. Mental health accounted for 30% of all inpatient costs. The majority of unregistered patients were male and aged 20-39 years. There were high levels of activity and cost in urban local authorities (LAs) (Birmingham and London) and LAs with links to military services (Salisbury, Richmondshire, Southampton). A high total inpatient cost was attributed to trauma, general medicine and mental health specialties. A high total outpatient cost was attributed to genitourinary medicine and trauma specialties.

Conclusions: Health care use by unregistered populations is an important consideration for resource allocation and planning health care services at national and local levels.