Response to: 'Correspondence on 'Concomitant use of oral glucocorticoids and proton pump inhibitors and risk of osteoporotic fractures among patients with rheumatoid arthritis: a population-based cohort study' by Gong and Zhang and Lin et al.

We read with much interest the two correspondences on our recently published paper by Lin et al and Gong and Zhang in the Annals of the Rheumatic Diseases .1–3 We conducted a retrospective cohort study to evaluate the association between concomitant use of two commonly used medications in patients with rheumatoid arthritis (RA), that is, oral glucocorticoids (GCs) and proton pump inhibitors (PPIs), and risk of osteoporotic (OP) fractures. We used data from one of the largest primary care databases in the world, the Clinical Practice Research Datalink (CPRD). While this database is a rich source, it does have some inherent limitations. The first question of both correspondences addresses one of these limitations of the CPRD, that is, the absence of any direct measure of RA disease activity in the database, such as the Disease Activity Score in 28 joints. The values of C reactive protein (CRP) were also not available for all patients, and if available, not for the whole follow-up period. Therefore, we decided not to include CRP in the analyses, considering our on-treatment study design and importance of having information on covariates during all person-times from patients for the entire follow-up. We were aware of this limitation and mentioned this in the paper. We also reported our strategy to overcome …