Published on 21/12/2025
Determining When to Report SUSARs in Clinical Trials
What Is a SUSAR?
A Suspected Unexpected Serious Adverse Reaction (SUSAR) is an event that meets three critical criteria: it is serious, it is related to the investigational product, and it is unexpected compared to the Investigator’s Brochure (IB) or product label. Only when all three conditions are satisfied does an SAE qualify as a SUSAR, triggering expedited regulatory reporting obligations.
Understanding when to classify and report a SUSAR is one of the most challenging areas of pharmacovigilance. Investigators may identify seriousness, but causality and expectedness assessments are often sponsor responsibilities. Misclassification can result in regulatory findings, ranging from FDA Form 483 observations to EMA inspection warnings.
For example, a patient on an immune checkpoint inhibitor who develops autoimmune encephalitis requiring hospitalization would be classified as a SUSAR if encephalitis is not listed in the IB. By contrast, febrile neutropenia, though serious and related, would not be a SUSAR if it is an expected toxicity already described in the IB.
Global Regulatory Timelines for SUSARs
Expedited SUSAR reporting timelines are broadly harmonized across regulatory agencies but must be strictly observed:
- Fatal or life-threatening SUSARs: Must be reported within 7
FDA (21 CFR 312.32), EMA (EU CTR 536/2014), MHRA (UK rules), and CDSCO (India) all follow this framework. However, India adds a layer: investigators must report all SAEs to sponsors, ethics committees, and CDSCO within 24 hours, with causality analysis submitted within 10 days. This emphasizes that SUSAR reporting is both investigator- and sponsor-driven, depending on jurisdiction.
Case Examples of SUSAR Reporting
To illustrate, consider the following scenarios:
- Case 1: Patient on a Phase II oncology drug develops myocarditis requiring ICU admission. Serious, related, unexpected. Classification: SUSAR. Reporting: 7-day expedited report.
- Case 2: Patient on cisplatin develops nephrotoxicity requiring hospitalization. Serious and related but expected (listed in IB). Classification: SAE, not SUSAR. Reporting: aggregate DSUR.
- Case 3: Subject dies due to progressive tumor growth. Serious but unrelated. Classification: SAE only, not SUSAR.
- Case 4: Patient develops Guillain-Barré Syndrome after novel vaccine. Serious, unexpected, and related. Classification: SUSAR. Reporting: expedited 7-day report.
These examples highlight how careful classification drives reporting obligations. Sponsors must document justification for causality and expectedness in narratives and ensure consistency across databases.
Decision Framework for SUSAR Reporting
Clinical teams should use a structured decision tree to determine when to report a SUSAR:
- Is the event serious? If no → AE only.
- If serious, is it related to the investigational product? If no → SAE only.
- If related, is it unexpected per IB/SmPC? If yes → SUSAR → expedited reporting.
Implementing this decision tree in electronic data capture (EDC) systems and pharmacovigilance databases helps automate classification and trigger expedited reporting workflows.
Documentation and Narrative Requirements
All SUSARs must be documented thoroughly. Narratives should include:
- Demographics and baseline characteristics of the patient.
- Dose, route, cycle/day of investigational product.
- Chronology of the event, including onset and resolution.
- Clinical findings, labs, imaging, and interventions.
- Investigator and sponsor causality assessments.
- Expectedness justification with IB/SmPC reference.
- Outcome and follow-up details.
Inspectors from FDA, EMA, or CDSCO often cross-check narratives with CRFs, safety databases, and TMF entries. Discrepancies in SUSAR documentation are one of the most common inspection findings.
Inspection Readiness and Common Pitfalls
Frequent issues identified during inspections include:
- Failure to meet 7-day reporting deadlines for fatal SUSARs.
- Inconsistent expectedness assessments between sites.
- Incomplete narratives lacking justification for causality.
- Discrepancies between CRF, narrative, and safety database entries.
To address these, sponsors should implement SOPs for SUSAR reporting, train staff on case classification, and reconcile SUSAR data monthly across all systems. Public trial registries like the Japan RCT Portal often include protocol safety sections highlighting SUSAR reporting obligations, which serve as benchmarks for global compliance.
Best Practices for SUSAR Reporting
To ensure compliance, trial teams should adopt the following:
- Implement clear SOPs defining SUSAR decision-making and timelines.
- Automate reporting triggers within safety databases.
- Provide regular training for investigators and coordinators.
- Maintain SUSAR line listings and reconciliation logs for inspection readiness.
- Update the IB promptly when new risks emerge to prevent over-reporting SUSARs.
By following these practices, sponsors and investigators ensure timely SUSAR reporting, protect trial participants, and maintain regulatory compliance across the US, EU, UK, and India.
