Two case-control studies will be conducted involving patients recruited from general and acute wards (Study B.1) and ICU (Study B.2). Each study will run in two sites, i.e. the Royal Infirmary of Edinburgh (RIE) and the Glasgow Royal Infirmary (GRI). The performance of the DelApp (index test) against reference standard diagnosis will be independently assessed by two trained raters, with one pair of raters on each site. As in our prior case-control studies, convenience samples will be used, where clinicians are asked to identify patients in the target groups.