Designing and validating a Hereditary Spastic Paraplegia-specific Quality of Life Rating Scale (HSPQoL)

Background Patients with Hereditary Spastic Paraplegia (HSP) report reduced quality of life (QoL) compared to the general population. Generic QoL measures do not address disease-specific aspects such as spasticity, access to specialty HSP clinics, and bladder symptoms. We designed and validated an HSP-specific QoL scale (HSPQoL), intended for use in standard clinical settings and clinical trials. Methods HSP-specific items were added to the RAND 36-Item Short Form Health Survey (SF-36) to form HSPQoL. Following literature review/expert input, 23 items were presented to a panel of HSP clinicians, patients, and patient representatives (n=12) using a modified Delphi process. Items were ranked for clarity and relevance (inclusion criteria: 80% consensus). Interviews with patients (n=5) assessed suitability, comprehension, clarity, and response options to additional items. Patients completed the HSPQoL and EQ5D-5L for evaluation of construct validity (correlation, exploratory factor analysis) and test-retest reliability. Results Following the modified Delphi process, 21/23 items met the inclusion criteria. Based on cognitive interview results, items were modified (n=4), removed (n=7), or added (n=3). Sixty-one participants completed the HSPQoL and EQ5D-5L. The HSPQoL was repeated with 19 patients: 15/17 additional items moderately to strongly correlated with pre-existing SF-36 subscores (Spearman correlation 0.319-0.771, p<0.05). Exploratory factor analyses showed high percentage of variance in the first component (>45%). HSPQoL demonstrated good internal consistency (Cronbach alpha 0.94), test-retest reliability (ICC 0.957), and convergent validity with EQ5D-5L (r=0.725). Conclusions Demonstrated validity and reliability of the HSPQoL confirms consideration of its use for assessing specific QoL in individuals with HSP.