Published on 21/12/2025
How to Code Ambiguous Verbiage in MedDRA for Clinical Trials
Introduction to Ambiguous Verbiage in Adverse Event Reporting
In clinical trials, adverse events (AEs) are initially reported by investigators in verbatim language, often reflecting patient statements or clinical notes. These terms are not always precise. Ambiguous expressions such as “feeling unwell,” “stomach upset,” or “heart problem” pose significant challenges during MedDRA coding. Unlike clear terms like “myocardial infarction” or “rash,” ambiguous terms require coder interpretation, which increases the risk of misclassification and regulatory non-compliance.
Regulators including the FDA, EMA, and CDSCO emphasize that accurate and consistent MedDRA coding is critical for pharmacovigilance and safety signal detection. Incorrect coding due to ambiguity can distort safety analyses and undermine the validity of DSURs, PSURs, and IND safety reports. To address this challenge, sponsors must implement SOPs, coding conventions, and training programs that guide coders in interpreting and coding ambiguous terms consistently.
Examples of Ambiguous Verbiage in Clinical Trials
Ambiguity often arises because investigators record patient experiences in lay language. Below are common examples and potential MedDRA interpretations:
| Investigator Term | Possible Interpretations | Preferred PT Options | Challenges |
|---|---|---|---|
| Stomach upset | Dyspepsia, abdominal pain, nausea | Dyspepsia / Abdominal discomfort | Vague term, may reflect multiple GI conditions |
| Heart problem | Arrhythmia, angina, heart failure | Requires clarification before coding | Non-specific; could map to several SOCs |
| Feeling unwell | Malaise, fatigue, dizziness | Malaise (generalized term) | Lacks clinical context |
| Fits | Seizure, convulsion, epilepsy | Convulsion | Must distinguish between acute and chronic condition |
These examples highlight the complexity of coding ambiguous terms. Without adequate conventions, coders may apply different PTs across trials, leading to inconsistent datasets.
Risks of Incorrect Coding Due to Ambiguity
Ambiguous coding errors can have serious consequences:
- Signal distortion: Misclassification of AEs can mask or exaggerate safety signals.
- Regulatory findings: Inspectors often flag inconsistencies in coding of ambiguous terms.
- Data fragmentation: Similar events coded differently across trials prevent accurate pooling of safety data.
- Audit deficiencies: Lack of documentation on coding decisions may be cited as a GCP non-compliance.
For instance, if “fainting” is coded as “Loss of consciousness” in one trial and “Syncope” in another, regulators may question the reliability of cross-study safety analyses. Consistency is therefore paramount in ambiguous coding cases.
Strategies for Handling Ambiguous Verbiage
Sponsors and CROs can manage ambiguity by applying structured strategies:
- Request clarification: Where possible, query the investigator for more detail before final coding.
- Use general PTs: When specifics are lacking, coders may assign broader PTs such as “Malaise.”
- Follow SOP conventions: Coding conventions should define how ambiguous terms are consistently coded.
- Flag for review: Ambiguous cases should undergo medical review by safety physicians.
- Document rationale: Coders should record the reasoning for selected PTs in audit trails.
For example, a sponsor SOP may state: “All reports of ‘feeling unwell’ should be coded as PT ‘Malaise’ unless additional clinical details are available.” Such conventions reduce variability and inspection risks.
Regulatory Expectations and Inspections
Regulators expect coders to demonstrate traceability in coding decisions for ambiguous terms. Common inspection findings include:
- Inconsistent PT selection across similar events.
- Failure to query investigators for clarification.
- Lack of documentation explaining coding rationale.
- Use of auto-coding without manual review of ambiguous terms.
To meet expectations, sponsors should establish coding conventions, maintain training records, and conduct routine audits. Inspection readiness requires evidence that ambiguous coding decisions were consistent, justified, and traceable. Public registries such as the NIHR Be Part of Research platform highlight the importance of standardized terminology for global safety data consistency.
Best Practices for Coders
Best practices for handling ambiguous terms include:
- Maintain detailed coding conventions with common ambiguous terms and assigned PTs.
- Provide refresher training to coders on how to handle vague or incomplete terms.
- Ensure coders escalate complex cases to medical safety officers.
- Review ambiguous terms in coding quality audits.
- Update conventions after each MedDRA version release.
These practices ensure that ambiguous terms are consistently coded and that datasets remain reliable across trials and submissions.
Key Takeaways
Coding ambiguous terms in MedDRA requires coders to balance accuracy, consistency, and regulatory compliance. To achieve this, clinical teams must:
- Recognize common sources of ambiguity in investigator-reported terms.
- Develop SOPs and conventions for standardizing ambiguous coding decisions.
- Document rationale and maintain audit trails for inspection readiness.
- Train coders and escalate complex cases to medical experts.
- Perform quality reviews to ensure consistency across trials.
By following structured strategies, sponsors and CROs can minimize the risks of misclassification, ensure reliable pharmacovigilance data, and meet global regulatory expectations.