With increasing age, the risk of frailty rises due to deterioration of several physiological systems, reducing the body’s reserve capacity. Recognising this vulnerability during care encounters is important both for understanding prognosis and recovery goals, and for planning care to reduce adverse outcomes.

Traditional emergency department (ED) risk stratification methods often fail to detect risks related to frailty, which is why interest in incorporating frailty assessment in EDs has grown. Several instruments have been developed, including the Clinical Frailty Scale (CFS). The CFS has been evaluated across many specialties and is recommended for use in the ED. However, no such research has been conducted in Swedish EDs, and studies under real clinical conditions remain limited.

Therefore, this thesis aims to examine whether the CFS is a useful tool for assessing frailty in older ED patients in Sweden. Specifically, we sought to evaluate its interrater reliability, prognostic accuracy, feasibility and the perspectives of patients.Study I was an observational study assessing IRR by collecting independent CFS assessments from the physician, registered nurse, and assistant nurse responsible for the patient. IRR was assessed in 100 patients, with 300 assessments conducted. IRR was moderate to good, with an ICC of 0.78 (95% CI 0.72–0.84).

Study II examined the prognostic value of the CFS by collecting staff-assessed CFS scores for 1840 older patients. The primary outcome was 30-day mortality, compared between patients with and without frailty. We found that 30-day mortality was significantly higher in patients with frailty compared to those considered robust (7.9% vs 0.9%). Frailty was independently associated with 30-day mortality, with an odds ratio of 6.0 (95% CI 3.0–12.2) after adjusting for confounding factors.

Study III employed a mixed methods design to examine the feasibility of the CFS in an ED setting. We collected data on 4235 ED visits and explored staff experiences through a questionnaire. The overall assessment completion rate was 47%, with more completed in older age groups. The most frequently reported barrier to assessment was high workload. Staff generally perceived the CFS to be relevant, although some questioned its benefits for patients in the ED.

Study IV had a qualitative design and included video-recorded CFS assessments and interviews with patients. A thematic analysis was conducted. Most older patients perceived frailty screening as positive or indifferent, though the experience could further benefit from a better understanding of the assessment’s purpose and consequences. Patients emphasised the importance of relationship-oriented communication, influencing their willingness to share information about their lives.

The CFS demonstrates moderate to good IRR and a strong association with mortality, supporting its usefulness in the ED. However, barriers such as high ED workload and mixed staff perceptions regarding its relevance to ED care impact routine use. Older patients generally respond positively to CFS while it is indicated that it can be further improved with clearer explanations of its purpose and potential consequences.