All 4 randomised controlled trials were done outside the UK. The clinical experts explained that because of international guidelines on preventing pressure ulcers, overall standards of care are likely to be relatively consistent across different countries. Nonetheless, there may still be differences in terms of patient selection, length of hospital stay, staff ratios and the exact composition of care bundles. The committee noted the relatively high baseline incidence rate of pressure ulcers in the control arm of the trials compared with the EAC's estimate for the incidence in the NHS. It also noted that any benefits associated with Mepilex Border dressings observed in the trial were based on a small absolute number of pressure ulcer events. Moreover, the committee was aware that assessing and grading heel and sacral pressure ulcers is subjective, and the clinical experts confirmed that this often depends on individual staff experience. Healthcare professionals will often seek a second opinion to avoid the consequence of incorrect grading, and the availability of specialist tissue viability nurses across the NHS varies. The clinical experts confirmed that NHS acute care settings include a broad range of patients at risk of pressure ulcers, and that staff across different clinical areas will have different levels of expertise in preventing and recognising early evidence of pressure ulcers. Having considered these factors, the committee concluded that there were uncertainties about the generalisability of the evidence to NHS practice.