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. 2022 Jul 27;78(7):706–712. doi: 10.1136/thoraxjnl-2021-217858

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© Author(s) (or their employer(s)) 2023. Re-use permitted under CC BY. Published by BMJ.

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Study flow diagram. The Northwest London (NWL) Discover database contains all Secondary Uses Service (SUS) spells meeting either of the following criteria: (i) the patient is registered with a general practitioner in NWL or (ii) the SUS spell is for a hospital in NWL.