<qa>  What is the final visit of the previous istradefylline study?Group A: Patients who have completed double-blind treatment studies 6002-US-0 13, 6002- US-Ol S or 6002-EU-007 immediately prior to entering this open-label trial and may have had an interruption of study drug of 14 days or less. The screening visit for these patients will correspond to the final visit of the previous istradefylline study. 