Psychometric properties of the portuguese version of the chronic urticaria quality of life questionnaire (CU-Q2oL)

Abstract

Background: Chronic urticaria is defined as the appearance of urticarial lesions and/or angioedema during a period of more than six weeks. We aimed at developing the Portuguese version of the Chronic Urticaria Quality of Life Questionnaire (CU-Q2oL) and at testing its reliability and the content, construct and criterion validity. Methods: The forward-backward approach to a linguistic equivalence was followed, after which a clinical review and a cognitive debriefing with patients were performed. The intraclass correlation coefficient checked test-retest reliability with patients filling the same questionnaire with one week apart and the Cronbach’s alpha indicator assessed the internal consistency. Construct validity was tested by an exploratory factor analysis and by hypothesis tests involving sociodemographic and clinical patient characteristics, including the urticaria control test (UCT). On the other hand, criterion validity was tested through correlations with the Short-Form Health Survey SF-36, EQ-5D-5 L, and the Dermatology Quality of Life Index (DLQI). Results: A total of 162 patients from seven hospital units were included. The mean (standard deviation) age was 42.6 (13.3) and 81.6% were female. CU-Q2oL was entirely filled by all respondents. Internal consistency was 0.947 for the overall score, ranging from 0.661 (limits) to 0.899 (sleep problems) and the corresponding reproducibility indicator was 0.910, based on 23 patients and ranging from 0.711 (swelling) and 0.957 (looks). Exploratory factor analysis in general confirmed the original structure originally obtained by the authors. All CU-Q2oL dimensions were highly correlated with DLQI Index and differentiated well between males and females, and between different levels of wheals and pruritus. In addition, moderate negative correlations were found between Cu-Q2oL scores and the dimensions from SF-36 and EQ-5D-5 L. Conclusions: The satisfactory metric properties confirmed the cultural adaptation and validity of CU-Q2oL into Portuguese population, providing the clinicians with a valid tool to evaluate the impact of chronic urticaria on patient’s QoL and therefore adjust their treatment.