A patient-reported pressure ulcer health-related quality of life instrument for use in prevention trials (PU-QOL-P): psychometric evaluation

INTRODUCTION: Pressure ulcer-specific patient-reported outcome (PRO) instruments should be used to inform patient care and provide a strong evidence base for interventions aimed at preventing pressure ulcers. The aim was to carry out a comprehensive evaluation of the psychometric properties of a PRO instrument designed to assess symptoms and functional outcomes in patients at high-risk of developing pressure ulcers, the PU-QOL-P instrument. METHODS: We modified the original PU-QOL instrument to be suitable for patients at high risk of pressure ulcer development based on feedback from patients, specialist nurses and PRO methodologists. The modified PU-QOL-P instrument was administered to a sub-set of patients participating in the PRESSURE 2 trial. Patients completed PU-QOL-P and SF12 instruments at baseline, weeks 1 and 3, and 30 days post-treatment. We undertook psychometric evaluation of the modified PU-QOL-P to test scale targeting, scaling assumptions, reliability, validity and responsiveness. RESULTS: The analysis sample consisted of 617 patients that completed both instruments at baseline. We found that the PU-QOL-P instrument, consisting of nine PU-specific outcomes: three symptom and six function scales, meets established criteria for reliability, construct validity, and responsiveness. Internal consistency reliability was high with all scale Cronbach alpha > 0.795 (range 0.795–0.970). The factor analysis mostly supported the six-function scale structure. Scaling assumptions were satisfied; all item-total correlations above 0.30. Convergent validity was confirmed by significant correlations between hypothesized scales as expected. PU-QOL-P scales were responsive to change: mean scale scores from baseline to 30 days post-treatment were statistically significant for all scales apart the daily activities scale (effect sizes ranged from moderate to high). As expected, worse symptoms and functioning was observed in patients who had a category 1 or 2 PU compared to patients who did not have a PU. CONCLUSIONS: The PU-QOL-P provides a standardised method for assessing pressure ulcer-specific symptoms and functional outcomes for quantifying the benefits of associated interventions from the patient’s perspective. It can be used in research with adults at risk of pressure ulcer development in all UK healthcare settings. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1186/s12955-018-1049-x) contains supplementary material, which is available to authorized users.