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. 2018 Mar 25;8(3):e019475. doi: 10.1136/bmjopen-2017-019475

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© Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2018. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

This is an Open Access article distributed in accordance with the terms of the Creative Commons Attribution (CC BY 4.0) license, which permits others to distribute, remix, adapt and build upon this work, for commercial use, provided the original work is properly cited. See: http://creativecommons.org/licenses/by/4.0/

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Flow chart illustrating the planned selection of CPRD participants for objective 1 of the COPD real-world medicines effects study. Note in relation to step 5 (n~18 000) compared with step 1 (n~13 000): approximately 90% of the treated patients will also have been eligible as untreated patients, as they did not receive FP/SAL on their TORCH-eligibility date. This means that they will have at least one period of time during which they are untreated-eligible but then did subsequently go on to receive FP/SAL (meaning they have at least one period of time during which they are treated-eligible). If a person is included as both a treated and untreated participant, they will be contributing different periods of their person-time to each cohort (pre-FP/SAL treatment for the untreated vs post-FP/SAL treatment for treated), and this is handled in the analysis by assigning different index dates. COPD, chronic obstructive pulmonary disease; CPRD, UK Clinical Practice Research Datalink; FP/SAL, fluticasone propionate+salmeterol.