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

Purpose: 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).

Methods: 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).

Results: 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).

Conclusions: QUALAS-A is a short, valid HRQOL tool for adults with SB.