The psychometric properties of the Parkinson's Impact Scale (PIMS) as a measure of quality of life in Parkinson's disease

We have previously designed and validated a 10-item bilingual questionnaire, the Parkinson's Impact Scale (PIMS), as a disease-specific instrument to measure the impact of Parkinson's disease (PD) on the quality of life of patients with PD. In this paper we extend the psychometric assessment of PIMS to a new set of patients, in the context of a cross-over trial by Hoffman-La Roche Ltd, comparing two doses of tolcapone in 116 PD patients who had developed wearing off effect on levodopa. Using data from this trial, we evaluate PIMS' test retest reliability, construct validity, sensitivity and responsiveness to change. Validation is carried out by correlating the PIMS scores with corresponding UPDRS subscales and with the Schwab and England scale. We show that PIMS has excellent psychometric properties, and can therefore be used not only in clinical trials but also to identify quickly potential problems in major subjective areas of PD patients' lives, in order to refer them effectively to appropriate providers of assistance. (C) 2003 Elsevier Science Ltd. All rights reserved.