Centers for Disease Control and Prevention (CDC), National Center for Health Statistics (NCHS).
215 Outpatient visits where patient was seen before in clinic or practice, United States, 2001–2002, by
CDC, NCHS, National Ambulatory Medical Care Survey (NAMCS) and National Hospital Ambulatory Medical Care Survey (NHAMCS)—Outpatient Departments.
Number of visits to office-based physicians and hospital outpatient departments.
Number of visits to office-based physicians and hospital outpatient departments where patient was seen before in a clinic or practice.
The NAMCS/NHAMCS question is "has patient been seen in this clinic before?" or "have you or anyone in your practice/department seen patient before?"