Validity and reliability of the Waterlow scale for assessing pressure injury risk in critical adult patients: A multi‐centre cohort study

Abstract

Aim

To evaluate the predictive validity and reliability of the Waterlow scale in critically adult hospitalised patients.

Design

A multi-centre cohort study.

Methods

This study was conducted in 72 intensive care units (ICUs) in 38 tertiary hospitals in Gansu Province, China. All adults admitted to the ICU for greater than or equal to 24 h without pressure injury (PI) on admission were screened by the Waterlow scale on admission, during ICU stay and ICU discharge from April 2021 to February 2023. Receiver operating characteristic (ROC) curves were used to determine a potential cut-off value for critical adult hospitalised patients. Cut-off values were then determined using Youden's index, and sensitivity, specificity, positive predictive value, negative predictive value and accuracy were calculated based on these cut-off values. Test–retest reliability was used to evaluate inter-rater reliability.

Results

A total of 5874 critical patients on admission were included, and 5125 of them were assessed regularly. The area under curve (AUC) was 0.623 (95% CI, 0.574–0.690), with a cut-off score of 19 showing the best balance among sensitivity of 62.7%, specificity of 57.4%, positive predictive value of 2.07% and negative predictive value of 99.08%. The test–retest reliability between the first assessment and the regular assessment was 0.447.

Conclusions

The Waterlow scale shows insufficient predictive validity and reliability in discriminating critical adults at risk of PI development. To further modify the items of the Waterlow scale, exploring specific risk factors for PI in the ICU and clarifying their impact degree was necessary. Risk predictive models or better tools are inevitable in the future.

Patient or Public Contribution

Patients or family members supported nurses with PI risk assessment, skin examination and other activities during the inquiry.