title: Proficiency testing and quality control programs.
mesh_terms: D006801:Humans; D013287:Illicit Drugs / Q000032:analysis; D007753:Laboratories; D011786:Quality Control; D019966:Substance-Related Disorders / Q000175:diagnosis*; D014481:United States; D014556:Urine / Q000032:analysis
chemical_list: D013287:Illicit Drugs