What is it? Why is it important?

An Interim Analysis (IA) is done before all data collection is complete in order to evaluate study safety and efficacy while the study is still ongoing, such as:

  • Safety concerns (e.g. a potentially high frequency of adverse events during study treatment)
  • Efficacy concerns (e.g. treatment effect compared to placebo is highly superior or has no added benefit)

Timing and rational of an IA must be documented in the study protocol.


An IA can also be beneficial in studies lasting for long periods of time. This might facilitate data cleaning during study conduct and guarantee data quality. In addition, IAs including data publications might be an integral strategy of longitudinal studies.

In order to protect participant safety and rights the Ethics Committee (EC) might request that an IA be performed during study conduct.

What do I need to do?

As a SP-INV:

  • Describe the rational and requirement of an IA in your study
  • Plan the appropriate timing of an IA (e.g. upon inclusion of 10 study participants, after 6 month study conduct months, on a quarterly basis)
  • Frequency and rational for repeated IAs
  • Type of statistical analysis used
  • Describe implications based on analytical results (e.g. upper- lower tolerability defining study continuation, adaptations, or study stop)
  • Plan to set-up a DSMB who provides expert advice on how to proceed with the study


A Data Safety Monitoring Board (DSMB) consists of a group of experts in relevant areas, and which are independent of the study.


The DSMB board reviews the accumulated data and findings from an IA and advises the SP-INV on the continued:

  • Safety of study participants
  • Validity of the study
  • Scientific merit of the study.

Where can I get help?

Your local CTU can support you with experienced staff regarding this topic


ICH GCP E6(R2) – see in particular guidelines

  • 5.4.1 Interim report
  • 5.5 Trial Management, data handling, and record keeping
  • 6.9.1 Statistics, interim analysis


ICH E9 – Statistical Principals for Clinical Trials

  • 4 Trial conduct considerations


ISO 14155:2020 Medical devices (access liable to costs) - see in particular section

  • 6.2 Risk management
  • A.7 Statistical design and analysis
  • CTU – Clinical Trials Unit
  • DSMB - Data Safety Monitoring Board
  • EC - Ethic Committee
  • IA – Interim Analysis
  • ICH-GCP – International Council for Harmonisation - Good Clinical Practice
  • ISO – International Organization for Standardization
  • SP-INV – Sponsor-Investigator
Development ↦ Management ↦ Study Safety ↦ Interim Analysis

Provides some background knowledge and basic definitions

Basic Monitoring
Basic Drug or Device

Starts with a study idea

Ends after having assessed and evaluated study feasibility

Concept Drug or Device

Starts with confidence that the study is feasible

Ends after having received ethics and regulatory approval

Development Drug or Device

Starts with ethics and regulatory approval

Ends after successful study initiation

Set-Up Ethics and Laws
Set-Up Quality and Risk
Set-Up Drug or Device

Starts with participant recruitment

Ends after the last participant has completed the last study visit

Conduct Drug or Device

Starts with last study visit completed

Ends after study publication and archiving

Completion Statistics
Completion Drug or Device
Current Path (click to copy): Development ↦ Management ↦ Study Safety ↦ Interim Analysis

Please note: the Easy-GCS tool is currently under construction.