1. Reprints: Steven J. Steindel, PhD, Division of Laboratory Systems, Public Health Practice Program Office, Centers for Disease Control and Prevention, 4770 Buford Hwy, MS G-23, Chamblee, GA 30341.
2. From the Division of Laboratory Systems, Public Health Practice Program Office, Centers for Disease Control and Prevention, Chamblee, Ga (Dr Steindel, Ms Simon, and Mr Handsfield); and Westat Inc, Rockville, Md (Mr Rauch).