OBJECTIVES Submissions to Health Technology Assessment (HTA) bodies must include the most up-to-date information on comparator technologies. This enables HTA bodies to make fully informed decisions. In order to ensure up-to-date information is obtained, all relevant data sources should be searched. At present HTA method guidelines generally specify that a core set of databases comprising EMBASE, MEDLINE, MEDLINE-in-process and the Cochrane Library are searched. However, in an attempt to manage the increasing quantity of research, journals are publishing more articles ahead of print as online e-publications. E-publications ahead of print are identifiable in PubMed but are not indexed in EMBASE, MEDLINE or Cochrane.  METHODS We selected a NICE guideline published in June 2014 for ablation techniques in atrial fibrillation which searched for randomised clinical trials (RCT) in the common databases. We updated the searches in EMBASE, MEDLINE, MEDLINE-in-process and the Cochrane Library from the date of the last search, to identify any studies published since the guideline was published. We concurrently searched PubMed using a filter to identify studies only available as e-publications ahead of print. RESULTS We identified one RCT meeting the inclusion criteria that was retrieved by the search in PubMed but was not identified by searching in EMBASE, MEDLINE or Cochrane (all searches being run on the same date). CONCLUSIONS If studies are missed from systematic reviews there can be important implications on clinical efficacy comparisons. To produce the most up-to-date systematic review, with all available full papers it is necessary to search for e-publications ahead of print in PubMed as well as for all other publications in EMBASE, MEDLINE and Cochrane.