Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.
Cocaine urine toxicology
Percent of urine samples obtained at each follow-up that were positive for cocaine. Missing samples prior to dropout from follow-up were imputed as positive for use, whereas those missing after final follow-up obtained were considered missing.
