MedDRA Coding of Adverse Drug Reactions (ADRs): Ensuring Accuracy in Pharmacovigilance

Introduction

Pharmacovigilance serves as a cornerstone in safeguarding public health by monitoring the safety and effectiveness of medicinal products throughout their lifecycle. Among its core activities, the collection, assessment, and reporting of adverse drug reactions (ADRs) are crucial. However, for data to be meaningful and comparable across countries, sponsors, and regulators, a standardized medical terminology is essential.

MedDRA (Medical Dictionary for Regulatory Activities) fulfills this role. Developed under the International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use (ICH), MedDRA provides a globally harmonized terminology that facilitates uniform recording, coding, and retrieval of medical information. It has become an indispensable tool for clinical trials, post-marketing surveillance, regulatory reporting, and signal detection.

This article explores the significance of MedDRA coding in pharmacovigilance, detailing its structure, principles, best practices, and impact on global drug safety.

What is MedDRA and Why is It Important for ADR Coding?

MedDRA is an internationally standardized medical terminology designed to support the entire regulatory process, from clinical development to post-marketing safety monitoring. It is widely used by pharmaceutical companies, contract research organizations (CROs), regulatory authorities, and academic institutions.

The importance of MedDRA in ADR coding cannot be overstated. Without a unified vocabulary, ADR descriptions would differ across regions and organizations, leading to data fragmentation, misinterpretation of safety signals, and regulatory non-compliance.

Using MedDRA ensures:

• Consistency and accuracy in medical term interpretation.
  
  
• Global harmonization across multiple regulatory jurisdictions such as FDA, EMA, PMDA, and NAFDAC.
  
  
• Efficient signal detection through structured data aggregation.
  
  
• Compliance with ICH guidelines, enabling seamless electronic submission of safety reports (E2B(R3) standards).
  
  

MedDRA Structure: A Five-Level Hierarchy for Precision

MedDRA uses a five-level hierarchical structure that organizes medical concepts from broad classifications to highly specific terms, making it both flexible and precise.

1. System Organ Class (SOC) – The broadest level, grouping terms by etiology, manifestation site, or purpose (e.g., Cardiac disorders, Nervous system disorders).
   
   
2. High Level Group Term (HLGT) – Organizes related High Level Terms into broader categories (e.g., Cardiac arrhythmias).
   
   
3. High Level Term (HLT) – Groups Preferred Terms with similar characteristics (e.g., Supraventricular arrhythmias).
   
   
4. Preferred Term (PT) – Represents a unique, standardized medical concept (e.g., Atrial fibrillation).
   
   
5. Lowest Level Term (LLT) – Includes synonyms, spelling variants, and lay terms (e.g., Afib, Atrial fib).
   
   

Example Scenario:

Reported ADR: “Patient experienced irregular heartbeat.”

• LLT: Irregular heartbeat
  
  
• PT: Arrhythmia
  
  
• HLT: Cardiac arrhythmias
  
  
• HLGT: Cardiac arrhythmias
  
  
• SOC: Cardiac disorders
  
  

This hierarchical design allows pharmacovigilance professionals to code at the most specific level (LLT) while still enabling aggregation at higher levels for analysis and regulatory reporting.

Principles of MedDRA Coding for ADRs

MedDRA coding requires adherence to internationally recognized guidelines, specifically the MedDRA Term Selection: Points to Consider (MTS:PTC) document. These principles include:

• Code what is reported: Do not infer or assume medical diagnoses beyond the provided information.
  
  
• Select the most specific LLT: Always code at the lowest level available to capture detailed information.
  
  
• Do not combine concepts: Each reported ADR should be coded separately.
  
  
• Capture all relevant information: Multiple ADRs in one report should each be coded individually.
  
  
• Stay neutral: Avoid making clinical judgments; coding should reflect the reporter’s words as accurately as possible.
  
  

The MedDRA Coding Workflow for ADRs

1. Review the Reporter’s Narrative
   Read the description thoroughly. For example, “Patient complained of chest pain and dizziness after taking the drug.”
   
   
2. Identify Relevant Medical Concepts
   Extract key terms from the narrative without interpretation (e.g., chest pain, dizziness).
   
   
3. Search for Matching LLTs in MedDRA
   Use a MedDRA browser or an integrated coding tool in your safety database.
   
   
4. Select Appropriate LLTs and Verify Accuracy
   Example:
   
   
5. • Chest pain → LLT: Chest pain (PT: Chest pain)
     
     
   • Dizziness → LLT: Dizziness (PT: Dizziness)
     
     
6. Apply Quality Control
   Double-check coding decisions, especially for ambiguous or complex cases.
   
   

Challenges in MedDRA Coding and How to Address Them

1. Ambiguous or Vague ADR Descriptions

Example: “Patient felt unwell.”

Solution: Use a non-specific LLT such as Feeling abnormal, but request clarification when possible.

2. Multiple ADRs in One Narrative

Reports often contain multiple symptoms or conditions.

Solution: Code each ADR separately to maintain data integrity.

3. Synonyms and Local Language Variations

In regions like Africa and Asia, reporters might use non-medical terms.

Solution: MedDRA includes synonyms in LLTs, but coders must be familiar with local expressions.

4. Keeping Up with MedDRA Updates

MedDRA is updated twice yearly (March and September).

Solution: Always use the latest version and train staff on changes.

Best Practices for Accurate MedDRA Coding

• Regular Training: Ensure coders are familiar with the current MedDRA version and MTS:PTC guidelines.
  
  
• Use Coding Software: Automated tools integrated into pharmacovigilance systems can reduce manual errors.
  
  
• Implement Quality Checks: Peer review and periodic audits help maintain consistency.
  
  
• Document Coding Decisions: Maintain a clear rationale for each coding choice for audit and compliance purposes.
  
  
• Stay Updated: Participate in MedDRA webinars and ICH training programs.
  
  

The Future of MedDRA Coding: Automation and AI

As pharmacovigilance evolves, Artificial Intelligence (AI) and Natural Language Processing (NLP) are being integrated into ADR coding systems to improve efficiency and accuracy. Automated MedDRA coding tools can scan narratives, suggest LLTs, and learn from human decisions over time.

Other trends include:

• Integration with Electronic Health Records (EHRs) for real-time safety monitoring.
  
  
• Improved multilingual support, critical for emerging markets.
  
  
• Predictive analytics for proactive signal detection.
  
  

Conclusion

MedDRA coding is a critical component of pharmacovigilance operations, ensuring that ADR data is standardized, reliable, and globally interpretable. Accurate coding not only fulfills regulatory requirements but also enhances signal detection, risk assessment, and patient safety.

As the pharmaceutical industry embraces digital transformation, the role of MedDRA will continue to expand, supported by automation, AI, and global harmonization efforts. Organizations that invest in robust coding practices, continuous training, and advanced tools will be better positioned to meet regulatory expectations and protect public health.

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