Inclusion and exclusion criteria for index procedure
We identified ESS using the Office of Populations Censuses and Surveys
Classification of Interventions and Procedures version 4 (OPCS-4) codes:
E081, E132, E133, E142, E143 or E148 were used in the first position in
the procedural record together with the code Y761 (for functional ESS)
anywhere in the procedural record. Descriptions of the definitions of
these codes are given in Supplementary material Table S1.Patients were only included if the clinical specialty listed was ENT.
Patients were also excluded where:
- The procedure was non-elective
- The patient was aged <17 years.
- Patients with a diagnosis of any of the following conditions anywhere
in the diagnostic record for the index admission: malignant neoplasm,
vasculitis, granulomatosis intracranial and intraspinal abscess and
granuloma, granuloma and granuloma-like lesions of oral mucosa, cystic
fibrosis, diseases of bronchus and cerebrospinal fluid leak without
diagnosis of sinusitis or nasal polyp. Patients undergoing
trans-sphenoidal pituitary surgery were also excluded. The OPCS-4 and
International Statistical Classification of Diseases and Related
Health Problems, tenth revision (ICD-10) codes used to define these
procedures are given in Supplementary material Table S1 .
Patients with malignant neoplasm and with the other conditions described
would not routinely be considered for day-case surgery, although some
are likely to be suitable for, and undergo day-case surgery.
To ensure all datapoints were independent of one another at a patient
level, only the chronologically first recorded index procedure for
anyone who had more than one procedure during the study period was
included in the dataset. The data extraction process is summarised inSupplementary material Figure S1 .