While an increasing amount of literature is published 'open access', a substantial proportion remains behind journal paywalls. Literature reviews require access to all full-text publications that may be relevant to the research question. Failure to consider all relevant records may result in missing key evidence. Although researchers with access to university libraries can obtain many articles without fees, patients, organisations or charities face a direct cost to access these paywalled articles. This investigation aimed to estimate the proportion of literature behind paywalls to determine the burden of accessing these articles for those without journal subscriptions.
We retrospectively examined three types of literature review in a range of study areas: one systematic literature review (SLR) investigating familial hypercholesterolaemia, one rapid review (RR) in the field of reproductive health and one pragmatic literature review (PLR) investigating drug repurposing for rare diseases. We calculated the proportion of relevant articles after abstract screening that were behind paywalls and obtained the lowest cost to access these (including temporary access) from relevant journal websites.
The proportion of articles behind paywalls was similar in the SLR (24%) and the PLR (30%), but higher in the RR (52%). Total costs for accessing full texts, as calculated from the lowest price per article, were £320 in the SLR (13/54 articles) and £1322 in the PLR (46/151 articles). In the RR, the cost was £2687 to £2840 for 72/139 articles, with the higher price including the cost of four journal subscriptions where price per individual article was unavailable. Article costs were highly variable by publisher and journal. In none of the reviews was it more cost-saving to purchase a journal subscription instead of individual articles.
Up to ~50% of the articles required at the full-text screening stage were behind a paywall. The highest proportion (52%) may have resulted from the exclusion of congress abstracts from the RR, which are often freely available in journal supplements. While further investigation is required to examine the impact of excluding paywalled articles on the conclusions drawn from literature reviews, the cost of purchasing publications may be substantial and thus prohibitive to patients wishing to review all published literature.