Clinical Impression of Severity Index for Parkinson's Disease and Its Association to Health-Related Quality of Life.

Background: Clinical Impression of Severity Index for Parkinson's Disease (CISI-PD) is a simple tool that can easily be used in clinical practice. Few studies have investigated the relationship between health-related quality of life and the CISI-PD.

Objective: To analyze the association of CISI-PD scores with those of generic (EQ-5D-5L) and Parkinson's disease (PD) disease-specific (Parkinson's Disease Questionnaire-8 [PDQ-8]) health-related quality of life assessments.

Methods: Persons with idiopathic PD in the Swedish Parkinson's Disease registry with simultaneous registrations of CISI-PD and EQ-5D-5L and/or PDQ-8 were included. Correlations with EQ-5D dimensions were analyzed. The relationships between the CISI-PD, EQ-5D-5L, and PDQ-8 were estimated by linear mixed models with random intercept.

Results: In the Swedish Parkinson's Disease registry, 3511 registrations, among 2168 persons, fulfilled the inclusion criteria. The dimensions self-care, mobility, and usual activities correlated moderately with the CISI-PD (  = 0.60,  = 0.54,  = 0.57). Weak correlations were found for anxiety/depression and pain/discomfort (  = 0.39,  = 0.29) ( values < 0.001). The fitted model included the CISI-PD, age, sex, and time since diagnosis. The CISI-PD had a statistically significant impact on the EQ-5D and PDQ-8 ( values < 0.001).

Conclusions: The CISI-PD provides a moderate correlation with the EQ-5D and could possibly be useful as a basis for defining health states in future health economic models and serving as outcomes in managed entry agreements. Nonetheless, the limitation of capturing nonmotor symptoms of the disease remains a shortcoming of clinical instruments, including the CISI-PD.