A regression analysis of the Waterlow score in pressure ulcer risk assessment

Objective: To explore the predictive value of the Waterlow score, and the subscores of age and gender. Design: Logistic regression analysis was conducted on the two subscores of the Waterlow score, and the residual Waterlow score with gender and age removed. Receiver operating characteristic (ROC) analysis gave a quantitative measure of the classification ability of the Waterlow score. Setting: Burton, UK. Subjects: All admissions over a five-year period to the District General Hospital, a total of 150 015 admissions of 82 691 patients. Interventions: None. Main outcome measures: Area under the ROC curve for significant (as determined by logistic regression) variables. Results: Data were inaccurate in at least 44.7% of the records, and analysis was conducted on the 43 735 records for which no errors were apparent. Nine hundred and fifty-four patients had a pressure ulcer on admission (2.1%); 277 developed a pressure ulcer (0.6%). The Waterlow score was predictive of pressure ulcers. Age was predictive, and gender was not found to be a significant predictor. Conclusions: The Waterlow score may be improved and simplified by removing gender from the scoring system.