Author Affiliations: Centers for Disease Control and Prevention, National Center for Health Statistics, Hyattsville, Maryland (firstname.lastname@example.org).
To the Editor: Dr Tang and colleagues1 concluded that emergency department (ED) visit rates have been increasing most among Medicaid patients. We believe this conclusion may be unwarranted. The analysis does not appear to have incorporated changes that occurred over the years in the coding of the variable “primary expected source of payment” in the data source used by the authors, the National Hospital Ambulatory Medical Care Survey (NHAMCS) conducted by the National Center for Health Statistics (NCHS). The only information on payment sources that NHAMCS collected from 1997 through 2004 was the primary expected source of payment.2 Starting in 2005, hospital respondents could indicate multiple expected sources of payment per visit and did not designate a primary source. From 2005 through 2007, the data files included separate variables for each expected payment source plus a variable that assigned the primary expected source using a hierarchy with Medicaid first, followed by Medicare, private insurance, worker's compensation, self-payment, and no charge.
Sonnenfeld N, Decker SL, Schappert SM. Trends in Emergency Department Visits Among Medicaid Patients. JAMA. 2011;306(11):1202–1203. doi:10.1001/jama.2011.1326