Abstract: Explores and identifies factors associated with nurse concern when patient deterioration is recognised in the absence of an emergency activation score such as early warning scoring (EWS) or the physiologically-unstable patient (PUP) tool. Describes the two phases of the multi-site and mixed-methods study: retrospective chart review of 19,326 referrals for emergency assistance; and seven focus group discussions with 29 nurses about what they do when concerned about patient deterioration in the absence of an EWS. Highlights the role of nurse expertise, knowledge and skill in identifying patient deterioration prior to the activation score on an EWS.