Coding and classification in drug statistics – From national to global application

SUMMARYThe Anatomical Therapeutic Chemical (ATC) classification system and the defined daily dose (DDD)was developed in Norway in the early seventies. The creation of the ATC/DDD methodology was animportant basis for presenting drug utilisation statistics in a sensible way. Norway was in 1977 also thefirst country to publish national drug utilisation statistics from wholesalers on an annual basis. Thecombination of these activities in Norway in the seventies made us a pioneer country in the area of drugutilisation research. Over the years, the use of the ATC/DDD methodology has gradually increased incountries outside Norway. Since 1996, the methodology has been recommended by WHO for use ininternational drug utilisation studies. The WHO Collaborating Centre for Drug Statistics Methodologyin Oslo handles the maintenance and development of the ATC/DDD system. The Centre is now responsiblefor the global co-ordination. After nearly 30 years of experience with ATC/DDD, the methodologyhas demonstrated its suitability in drug use research. The main challenge in the coming years is toeducate the users worldwide in how to use the methodology properly.