Reliability and validity of a frailty assessment tool in specialized burn care, a retrospective multicentre cohort study

Abstract

Background: Frailty is a predictor of adverse outcomes in elderly patients. The Canadian Study of Health and Aging Clinical Frailty Scale (CFS) is an often-used frailty assessment instrument. However, the CFS's reliability and validity in patients with burn injuries are unknown. This study aimed to assess the CFS's inter-rater reliability and validity (predictive validity, known group validity and convergent validity) in patients with burn injuries treated to specialized burn care.

Methods: A retrospective multicentre cohort study was conducted in all three Dutch burn centres. Patients aged ≥ 50 years with burn injuries, with a primary admission in 2015-2018, were included. Based on information in the electronic patient files, a research team member scored the CFS retrospectively. Inter-rater reliability was calculated using Krippendorff's α. Validity was assessed using logistic regression analysis. Patients with a CFS ≥ 5 were considered frail.

Results: In total, 540 patients were included, with a mean age of 65.8 years (SD 11.5) and a Total Body Surface Area (TBSA) burned of 8.5%. The CFS was used to assess frailty in 540 patients and the reliability of the CFS was scored for 212 patients. Mean CFS was 3.4(SD 2.0). Inter-rater reliability was adequate, Krippendorff's α 0.69 (95%CI 0.62-0.74). A positive frailty screening was predictive of a non-home discharge location (OR 3.57, 95%CI 2.16-5.93), a higher in-hospital mortality rate (OR 1.06-8.77), and a higher mortality rate within 12 months after discharge (OR 4.61, 95%CI 1.99-10.65) after adjustment for age, TBSA, and inhalation injury. Frail patients were more likely to be older (for<70 vs. ≥70 years odds ratio 2.88, 95%CI 1.95-4.25) and their comorbidities were more severe (ASA ≥3 vs 1-2 OR 6.43, 95%CI 4.26-9.70) (known group validity). The CFS was significantly related (r_Spearman=0.55) to the Dutch Safety Management System (DSMS) frailty screening, reflecting a fair-good correlation between the CFS and DSMS frailty screening outcomes.

Conclusion: The Clinical Frailty scale is reliable and has shown its validity, including its association with adverse outcomes in patients with burn injury admitted to specialized burn care. Early frailty assessment with the CFS must be considered, to optimize early recognition and treatment of frailty.

Keywords: Burn injury; Clinical frailty scale (CFS); Frailty; Reliability; Validity.