Disability in Italian neurosurgical patients: validity of the 12-item World Health Organization Disability Assessment Schedule.

The aim of the study was to assess factor structure, internal consistency and validity of the Italian version of the World Health Organization Disability Assessment Schedule 12-item version (WHODAS-12) in patients scheduled for neurosurgical procedures for brain tumours, cerebrovascular or spinal diseases. Disability was assessed with the WHODAS-12, quality of life with the eight-item European Health Interview Survey-Quality of Life, well-being with the Psychological General Well-Being Index-Short and general health with the Karnofsky Performance Status (KPS) scales. Factor analysis was used to confirm WHODAS-12 one-factor structure; root mean square error of approximation (RMSEA) and χ2/d.f. ratio were used to test the model fit. Internal consistency was assessed with Cronbach's α coefficient, item-total correlation and interitem correlation; convergent validity was assessed with Pearson's coefficient and discriminative validity was assessed with the t-test, dividing patients between those with KPS greater than 90 and KPS of 90 or less. The one-factor structure was confirmed (RMSEA=0.079; χ2/d.f.=2.16) and internal consistency was adequate. Correlations between the three outcome measures were significant, negative and moderate; the t-test showed disability scores to be statistically significantly higher in patients with KPS of 90 or less. Our results confirm factor structure and validity of WHODAS-12 in Italian neurosurgical inpatients; we therefore support its use in neurosurgery departments.