United States Center for Disease Control and PreventionGiven the importance of laboratory test results, CDC 's National Center for Environmental Health has vital programs to help assure the quality of these data can be accurate. CDC offers customized quality assurance and standardization programs to help laboratories improve the quality and reliability of their measurement procedures. The services CDC provides include reference materials, proficiency testing, training, guidelines, and consultations. Each CDC laboratory quality assurance and standardization program is voluntary, and most are free of charge.