gms | German Medical Science

Introduction: Hereditary spastic paraplegia (HSP) is a heterogeneous group of genetic neurodegenerative diseases. The well-validated Spastic Paraplegia Rating Scale (SPRS) is being broadly used to measure disease severity and progression. However, this scale does not provide any information about health-related quality of life (HRQoL) of HSP patients. The aim is to develop a patient reported outcome specific for HSP via HRQoL questionnaires.

Methods: First, semi-structured guided interviews were conducted with 36 patients and 18 caregivers. Then, based on qualitative data analysis, two similar pilot questionnaires in German for patients and caregivers, both evaluating the patient’s HRQoL, were developed and sent to 91 HSP-households. Item validation and overall improvement was conducted by item analysis. Improved questionnaires were forwarded as online versions to larger groups to confirm validity and reliability. To discover and to confirm the underlying structure, exploratory factor analysis (EFA) and confirmatory factor analysis (CFA) were conducted. Validation was further confirmed by (Pearson’s) correlations to a generic HRQoL and to a disease severity questionnaire. Reliability was verified by Cronbach’s alpha and retest reliability.

Results: Based on the interviews, 45 items were developed for each pilot questionnaire. Item analysis could be conducted on the responses of 65 patients and 53 caregivers, leading to item modifications with 28 remaining items for the main validation. In total 234 patient’s responses and 55 caregiver’s responses were used for the main validation. Five subdomains could be detected via EFA. Based on the EFA, three additional items were deleted. Correlations with the retest are above or very close to 0.8 for all subdomains. Cronbach’s alpha is above 0.8 for three out of five subdomains. Correlations with the generic HRQoL score are all positive and with the disease severity score all negative, as expected. The correlations between the questionnaire distributed to patients and the one distributed to caregivers is above or close to 0.7 for all subdomains. CFA suggested that the model with five subdomains is acceptable.

Discussion: The five subdomains discovered by the EFA can be easily clinically interpreted. The retest and Cronbach’s alpha show the questionnaire’s reliability. Especially, the correlations between the disease severity score and the HSP HRQoL are large for subdomains concerning mainly HSP symptoms, and low for other subdomains, showing the questionnaire’s validity as well as the necessity for a HRQoL-questionnaire. The high correlations between the questionnaire for patients and for caregivers imply that the latter is reliable as a proxy questionnaire.

Conclusion: We developed a valid and reliable HRQoL-questionnaire and proxy questionnaire for patients with HSP with five clinically interpretable subdomains and 25 items. A score ranging from 0 to 100 represents the HRQoL in total and per subdomain. The high patient’s response rate of more than 70% in the pilot study shows the enormous importance of the HRQoL-assessment for HSP patients. The questionnaire can be implemented in clinical routine and studies to assess systematically HRQoL of HSP patients over the time. In a next step, the questionnaire can be translated and validated to different languages.

The authors declare that they have no competing interests.

The authors declare that a positive ethics committee vote has been obtained.