WHO Collaborating Centre for Drug Statistics Methodology

The WHO Collaborating Centre for Drug Statistics Methodology is an integral part of the World Health Organization (WHO) network, dedicated to the development and maintenance of the Anatomical Therapeutic Chemical (ATC) classification system and the Defined Daily Dose (DDD) system. These systems are crucial for the standardization of drug usage statistics and for facilitating international comparisons in drug utilization research.

Photograph of the WHO headquarters building in Geneva, Switzerland.

History

The WHO Collaborating Centre for Drug Statistics Methodology was established in 1982 in Oslo, Norway. It was created to address the growing need for a standardized system to classify drugs and measure drug consumption. The Centre's primary mission is to develop and maintain the ATC/DDD system, which is used globally by healthcare professionals, researchers, and policymakers.

Anatomical Therapeutic Chemical (ATC) Classification System

The ATC classification system is a tool for classifying drugs and other medical products according to the organ or system on which they act and their therapeutic, pharmacological, and chemical properties. The system is hierarchical, with drugs classified into five levels:

First level: The anatomical main group (e.g., cardiovascular system).
Second level: The therapeutic main group (e.g., antihypertensives).
Third level: The pharmacological subgroup (e.g., beta-blocking agents).
Fourth level: The chemical subgroup (e.g., selective beta-blocking agents).
Fifth level: The chemical substance (e.g., metoprolol).

The ATC system is continuously updated to reflect new scientific knowledge and changes in drug usage patterns.

Defined Daily Dose (DDD) System

The Defined Daily Dose (DDD) system is a statistical measure of drug consumption, defined as the assumed average maintenance dose per day for a drug used for its main indication in adults. The DDD system is used to standardize the comparison of drug usage between different drugs or between different health care environments. It provides a fixed unit of measurement independent of price, dosage form, and strength, allowing for the aggregation and analysis of drug consumption data.

Functions and Activities

The WHO Collaborating Centre for Drug Statistics Methodology performs several key functions:

**Development and Maintenance of ATC/DDD:** The Centre is responsible for the continuous updating and revision of the ATC/DDD system to ensure its relevance and accuracy.
**Training and Education:** The Centre provides training and educational resources to healthcare professionals and researchers on the use of the ATC/DDD system.
**Research and Development:** The Centre conducts research to improve the ATC/DDD system and to explore new methodologies for drug utilization studies.
**International Collaboration:** The Centre collaborates with other WHO collaborating centres, national and international organizations, and academic institutions to promote the use of the ATC/DDD system and to support drug utilization research globally.

Impact and Applications

The ATC/DDD system developed by the WHO Collaborating Centre for Drug Statistics Methodology has had a significant impact on drug utilization research and public health policy. Some of the key applications include:

**Drug Utilization Studies:** The ATC/DDD system is widely used in drug utilization studies to analyze patterns of drug use, identify trends, and evaluate the effectiveness of interventions.
**Public Health Surveillance:** The system is used in public health surveillance to monitor drug consumption and to detect potential issues related to drug safety and efficacy.
**Health Policy and Planning:** Policymakers use the ATC/DDD system to inform decisions on drug pricing, reimbursement, and formulary management.
**Clinical Practice:** Healthcare professionals use the system to guide prescribing practices and to ensure the rational use of medicines.

Challenges and Future Directions

Despite its widespread use and success, the ATC/DDD system faces several challenges:

**Complexity of Drug Classification:** The classification of new and complex drugs can be challenging, requiring continuous updates and expert input.
**Global Variability:** Differences in drug availability, prescribing practices, and healthcare systems across countries can complicate the application of the ATC/DDD system.
**Technological Advancements:** Advances in technology and the development of new therapeutic agents necessitate ongoing revisions to the system.

The future directions for the WHO Collaborating Centre for Drug Statistics Methodology include:

**Enhancing Global Collaboration:** Strengthening partnerships with international organizations and countries to promote the use of the ATC/DDD system.
**Improving Data Quality:** Developing new methodologies and tools to improve the accuracy and reliability of drug utilization data.
**Expanding Educational Outreach:** Increasing efforts to educate healthcare professionals and researchers on the use of the ATC/DDD system.