International guideline changes and the incidence of infective endocarditis: a systematic review

The objective of this study was to determine the impact on incident infective endocarditis (IE) of guideline recommendations to restrict indications for antibiotic prophylaxis. We conducted a systematic review according to the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guideline. PubMed and EMBASE databases were searched for articles published between 2007 and 2015 using mesh terms relevant to the research question. Included were English language articles published after 2009 that provided estimates of IE incidence before-and-after major international guideline changes. Seven studies were identified: 1 conducted in France, 4 in the USA and 2 in the UK. Only 1 study reported an increase in the rate of incident IE following guideline modification, and the remainder showed no change in upward (2 studies) or downward (4 studies) incidence trends. Study quality was generally poor for answering the question posed in this review, with serious risk of bias related to diagnostic ascertainment and unavailability of population risk data to adjust the incidence estimates. Moreover, the studies were often small, and relevant bacteriological data were not always available. Only 2 reported changes in antibiotic prescriptions, but these data were not linked to health records making it impossible to determine causal relations to changes in incident IE. The studies in this review were heterogenous in their design and variably limited by study size, duration of follow-up, diagnostic ascertainment, and absence of relevant prescription and bacteriological data. The studies were inconsistent in their conclusions and it remains uncertain what, if any, has been the impact of antibiotic prophylaxis guideline changes on the incidence of IE.