A definition of "on": patient diaries compared to the UPDRS

This study investigates the relationship of the Unified Parkinson's Disease Rating Scale (UPDRS) to the patient's perception that they are "on". Follo wing the first dose of medication, patients reported that they were "on" wh en their UPDRS-III reached a mean of 8 +/- 2, representing a decrease of 67 +/- 8% from their early morning rating. Patients reported that they were " off" when their UPDRS-III score increased to 20 +/- 5, representing an incr ease of 50 +/- 12% from their initial "on" score. A 67% improvement in the baseline UPDRS-III score may be useful in defining "on". (C) 1999 Elsevier Science Ltd. All rights reserved.