We thank the Editor for the opportunity to respond to Adam et al.'s letter. In our systematic review, we state ‘Potentially relevant articles were identified by the search strategy and title screened for relevance (n = 3, 152)’. Our search terms were peer-reviewed. An independent re-run of the search, to check whether we missed the papers in question, confirmed that the two papers authored by Adam et al.[3, 4] do not appear in the results.