Affiliations: [a] Serviço de Neurologia, Centro Hospitalar do Porto, Porto, Portugal
| [b] Unidade Multidisciplinar de Investigação Biomédica, Instituto Ciências Biomédicas Abel Salazar, Universidade do Porto, Porto, Portugal
Faculdade de Medicina da Universidade do Porto, Porto, Portugal
CINTESIS, Faculdade de Medicina da Universidade do Porto, Porto, Portugal
| [e] Sydney School of Public Health, University of Sydney, Sydney, Australia
| [f] Department of Clinical Neurosciences, Clinic of Neurology, Geneva University Hospital, Geneva, Switzerland
| [g] Department of Basic Neurosciences, Medical Faculty, University of Geneva, Geneva, Switzerland
Correspondence to: Alexandre Mendes, Serviço de Neurologia, Hospital de Santo António, Centro Hospitalar do Porto, Largo Prof. Abel Salazar, 4099-001 Porto, Portugal. Tel.: +351 936350136; E-mail: [email protected].
Abstract: Background: The rate of Parkinson’s disease (PD) progression varies widely between patients. Current knowledge does not allow to accurately predict the evolution of symptoms in a given individual over time. Objectives: To develop regression-based models of PD progression and to explore its predictive value in a three-year follow-up. Methods: At baseline, 300 consecutive PD patients were assessed using the Unified Parkinson’s Disease Rating Scale (UPDRS) - subscales II and III, Hoehn & Yahr (H&Y) and Schwab and England Independence Scale (S&E); and the Freezing of Gait Questionnaire (FOG-Q). UPDRS-III and H&Y were applied in OFF and ON medication conditions. An axial index was derived from the UPDRS-III. Based on multiple linear regression coefficients, algorithms were developed to adjust test scores to the characteristics of each individual. Sixty-eight patients were reevaluated three years later. Results: In the construction of the models, disease duration, age ≥70, age at disease onset ≥55, tremor as the first symptom alone, and medication description explained between 35% (UPDRS-III in ON) and 57% (axial index in ON) of the variance of test scores. The predictive r2 of the models in a 10-fold cross-validation ranged between 33% (UPDRS-III in ON) and 55% (axial index in ON and S&E in OFF). All measures, except UPDRS-III OFF, H&Y ON, and S&E ON, had moderate/good absolute agreement (intraclass correlation coefficient between 0.60 and 0.72) between baseline and follow-up. Conclusions: A cross-sectional assessment of a PD population allowed the development of models of disease progression, whose predictive value was validated on a three-year longitudinal study.
Keywords: Parkinson disease, disease progression, statistical models, validity of results