MedDRA is a terminology for coding all medical information obtained during all phases of development and marketing: Excluded from MedDRA MedDRA is organized with the following hierarchy (numbers are for MEdDRA 8.1): The 26 SOC: The dictionary allows multiaxial coding: certains PT terms can be found in more than one SOC. But, in each SOC, each PT is represented by only one HLT and one HLGT. Each PT has a primary pathway that must be used for the initial analysis.
LLT may be a non-current term MedDRA also supports Special Search Categories (SSC) that contain clinical concepts relative to a similar etiology that cross SOCs. They generally group PTs relevant to a disease or a syndrome. In MedDRA 7.0: MaeDRA also contains Standardized MedDRA Queries (SMQs). They will eventually replace SSCs. The result for a COOPERATIVE effort between CIOMS and ICH (MSSO). They are groupings of MedDRA terms, ordinarily at the Preferred Term (PT) level, that relate to a defined medical condition or area of interest. Terms included in a given SMQ may relate to relevant signs, symptoms, diagnoses, syndromes, physical findings, laboratory and other physiologic test data… In Production (as of 2005-10-11) Some details The dictionary is updated twice a year. Major updates are indicated by an increment of the first digit, minor ones by an increment of the second.

If a patient experiences a recurring given AE, this one is counted only once with a severity equal to the greatest severity of all occurrences.