Detailed Explanation
MedDRA provides the standardized terminology that enables consistent coding of adverse events, medical history, and other clinical observations across clinical trials, post-marketing surveillance, and regulatory submissions worldwide. Developed under the auspices of ICH and maintained by the MedDRA Maintenance and Support Services Organization, this hierarchical dictionary ensures that safety data can be aggregated, compared, and analyzed across different studies, sponsors, and regulatory jurisdictions using a common vocabulary.
The MedDRA hierarchy comprises five levels of increasing specificity. System Organ Classes represent the highest level, grouping terms by etiology, manifestation site, or purpose. High Level Group Terms and High Level Terms provide intermediate groupings that facilitate data retrieval and review. Preferred Terms represent distinct medical concepts used for clinical data entry and analysis, while Lowest Level Terms provide the most specific terminology available. This hierarchical structure allows safety data to be analyzed at multiple levels of granularity, from broad system organ class comparisons to specific preferred term frequencies.