Each file containing the universe of eligible patients will be sent to RTI, from which 475 patients from each Center s list will be randomly selected. RTI will send a list back to each Center indicating which 475 patient IDs were selected for inclusion in the survey. The Center staff will match selected patient back to their master list using the Study ID number to identify patients included in the survey. RTI will deliver 475 pre-paid patient survey packets to each Center. The packets will include all required items except a Patient Notification Letter, which is a cover letter introducing the study and provides instructions on how to complete the survey. To protect patient privacy, Center staff will be responsible for generating the mailing labels and personalized Patient Notification Letter, and mailing the packets.