QUAlity of Life Assessment in Spina bifida for Adults (QUALAS-A): development and international validation of a novel health-related quality of life instrument

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Abstract
Health-related quality of life (HRQOL) is important in spina bifida (SB) management. No clinically useful, comprehensive instrument incorporating bladder/bowel domains exists. We aimed to develop and validate a self-reported QUAlity of Life Assessment in Spina bifida for Adults (QUALAS-A). We drafted the 53-question pilot instrument using a comprehensive item generation/refinement process. It was administered to an international convenience sample of adults with SB and controls recruited online via social media and in person at outpatient SB clinics (January 2013–September 2014). Final questions were determined by: clinical relevance, high factor loadings and domain psychometrics in an Internal Validation Sample randomly selected from United States participants (n = 250). External validity was evaluated in United States and International External Validation Samples (n = 165 and n = 117, respectively). Adults with SB completed the validated general WHOQOL-BREF and International Consultation on Incontinence Questionnaire (ICIQ). Mean age of 532 participants was 32 years (32.7 % males, 85.0 % Caucasian), similar to 116 controls (p ≥ 0.08). There were 474 online and 58 clinical participants (61.1 % eligible). Face validity and content validity of the 3-domain, 15-question QUALAS-A were established by patients, families and experts. Internal consistency and test–retest reliability were high for all domains (Cronbach’s alpha ≥ 0.70, ICC ≥ 0.77). Correlations between QUALAS-A and WHOQOL-BREF were low (r ≤ 0.60), except for high correlations with Health and Relationships domain (0.63 ≤ r ≤ 0.71). Bladder and Bowel domain had a high correlation with ICIQ (r = −0.70). QUALAS-A scores were lower among adults with SB than without (p < 0.0001). QUALAS-A had good statistical properties in both External Validation Samples (Cronbach’s alpha 0.68–0.77). QUALAS-A is a short, valid HRQOL tool for adults with SB.

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