Which patients are included in the estimate of 90-day mortality in the 2018 report?

All patients aged 18 or over diagnosed between 1 April 2016 and 31 March 2017 who, according to NBOCA, underwent a major resection on or before 31st October 2017 (regardless of surgical urgency or curative intent).
Patients with cancer of the appendix and patients missing date of surgery or whose date of surgery is reported to be after their date of death will be excluded. Patients for whom ONS date of death is unavailable are excluded, and this will include patients who have a national data opt-out.

Further details about national data opt-out which replaced Type 2 objections from May 2018 is available from https://digital.nhs.uk/services/national-data-opt-out-programme