The challenge of opt-outs from NHS data: a small-area perspective.

[First paragraph] One of the founding principles of the NHS is that it offers comprehensive, universal and free public health services at the point of delivery. As a result, NHS data provide a huge and invaluable resource of routinely collected primary (e.g. visits to GP practices) and secondary (e.g. hospital admissions, outpatient appointments, A&E attendances) healthcare data covering near-100% of the population of England. NHS Digital has the responsibility for collecting and publishing data and information from across the health and social care system in England and controls the dissemination of these data. Detailed analysis of NHS data by public health and research institutions has the potential to considerably improve health and social care in England.