MedDRA Coding & Term Selection · Section 4.2
~7 min read · The Drug Safety Coach — Global PV Career Course
Key points
Full text
Every MedDRA code a coder selects sits inside a governance structure most people never see. ICH owns MedDRA outright; the Maintenance and Support Services Organization (MSSO) is contracted by the ICH MedDRA Steering Committee to maintain it day to day, and describes itself deliberately as a "custodian," not an owner. The Steering Committee—drawn from regulators including the FDA, EMA, MHRA, PMDA, Health Canada, and, since May 2025, China’s NMPA and Saudi Arabia’s SFDA—sets subscription rates, approves developmental plans, and meets with the MSSO regularly. The Japanese Maintenance Organisation (JMO) is a separate partner specifically for the Japanese-language version. None of this is trivia: it’s the reason MedDRA coded data is comparable across every regulator and every company that uses it.
Structurally, MedDRA is a five-level hierarchy: System Organ Class (27, e.g. Cardiac disorders) sits above High Level Group Term (>330), High Level Term (~1,700), Preferred Term (~27,000), and finally Lowest Level Term (~90,000) — currently around v29.0. Coding is always performed at the LLT, the level closest to how a case is actually reported, and only current LLTs may be selected for new coding; non-current terms (vague, ambiguous, outdated, truncated, or misspelled) are retained purely to preserve historical data for retrieval and trend analysis, never for fresh entries.
Three SOCs—Investigations, Surgical and medical procedures, and Social circumstances—are non multi-axial: PTs there only ever appear in that one SOC. Everywhere else, a PT can be represented in more than one SOC (a multi-axial terminology), which is what lets a term like Obesity cardiomyopathy or Influenza be retrieved correctly whether a reviewer is searching by cardiac disorder or by metabolic disorder, by infection or by respiratory disease. To stop that flexibility from causing double-counting in cumulative outputs, every PT is still assigned exactly one Primary SOC, following a defined rule set: PTs found in only one SOC are automatically primary there; disease/sign/symptom PTs go to their prime manifestation site; and congenital, neoplasm, and infection PTs default to their own dedicated SOC — in that priority order when more than one exception applies.
For a working PV professional, the practical takeaway is less about memorising counts and more about discipline: MedDRA’s structure is standardised precisely so that a case coded in Mumbai and a case coded in Basel land in the same place in a cumulative safety database. That only holds if nobody quietly reassigns a Primary SOC or invents a private "fix" for a term that looks wrong — which is exactly why the formal Change Request process exists, covered next alongside how term selection itself is meant to work.
Important
Do Not Alter MedDRA: users must never make ad hoc structural changes, including reassigning a term’s Primary SOC, even when a term looks incorrectly placed. If a term genuinely belongs somewhere else, the correct path is a Change Request to the MSSO via WebCR — not a private workaround that breaks consistency with every other organisation’s coded data.
Quick check
Test yourself before moving on — no pressure, just click an answer.
1. At which level of the MedDRA hierarchy does coding always take place?
2. Why is every PT assigned exactly one Primary SOC, even when it is represented in multiple SOCs?
MedDRA Five-Level Hierarchy (v29.0) — click a term
Every reported symptom gets coded from broad to specific: System Organ Class → High Level Group Term → High Level Term → Preferred Term → Lowest Level Term — the exact wording a patient or doctor used maps down to one PT.