Understanding individual participant data (IPD): what it is and why it matters

What is IPD?

Many people are often unsure what individual participant data (IPD) means in clinical trials. IPD refers to the raw, de-identified data collected from each person that takes part in a trial. This includes detailed, line-by-line information such as medical test results, health measurements, and responses to questionnaires.

When people mention “sharing IPD”, they mean sharing these data without any personal details – such as names or contact information. This is known as de-identified data.

Why are you asked about sharing IPD when registering a trial?

When registering a clinical trial on a World Health Organization (WHO)-approved registry, you need to indicate whether you plan to share de-identified IPD after the trial ends. This is required by the WHO1 and International Committee of Medical Journal Editors (ICMJE)2. Other stakeholders may also require IPD sharing:

Journals may ask for all IPD or IPD that supports published results, along with access to your trial protocol and statistical analysis plan, and
Funders may make IPD sharing a condition of grant funding.

You can update your IPD sharing decision at any time – during the trial or after it has finished.

Why does this matter?

There is growing support towards responsible sharing of de-identified IPD. Reasons for this include the potential to repurpose collected data for a variety of future research needs, and to maximise the return on investment – both in time and funding – of clinical trials.

The most common uses of shared IPD include3:

  1. Exploring new questions or hypotheses through secondary analyses
  2. Understanding how healthcare interventions work in specific groups of people through systematic reviews and meta-analysis – this may not be possible with only summarised (aggregated) data, and
  3. Understanding clinical trial methods.

Studies indicate that trial participants generally support responsible IPD sharing, provided it is done securely and ethically.

What are some of the concerns?

Concerns around sharing IPD are real4. These include its use in research that may have limited clinical relevance, poor study design, misinterpretation of data and results, and cases where IPD meta-analyses yield similar findings to aggregate data – raising questions about added value. Other concerns include significant time and costs to prepare IPD in a usable format for others.

However, these concerns are not unique to IPD sharing – they occur across research and can be addressed through good research practice and collaboration with experienced content experts so studies are well-designed and relevant to clinical or policy needs. 

How does the ANZCTR help?

The ANZCTR helps investigators:

  • Set conditions for how and when IPD can be shared, and
  • Comply with WHO and ICMJE requirements through a guided section that supports completion of the IPD sharing component.

National catalogue to request access to IPD

In Australia, the national catalogue - Health Data Australia - allows researchers to provide high-level trial information (not IPD itself) and enables other researchers to request access to IPD. The catalogue is part of the Health Studies Australia National Data Asset (HeSANDA) initiative, co-designed by the Australian Research Data Commons (ARDC) and researchers. The ANZCTR contributed to the development of this initiative. If you wish to contribute your trial’s information (free of charge), visit Health Data Australia.

1World Health Organization (WHO). WHO Trial Registration Data Set (Version 1.3.1). Item 24 – IPD sharing statement. Available at: WHO data set.
2International Committee of Medical Journal Editors (ICMJE). Publishing and editorial issues: Clinical trials – 2. Data sharing. Available at: ICMJE | Recommendations | Clinical Trials
3Coady SA et al. 2017. Use of the National Heart, Lung, and Blood Institute Data Repository. NEJM. DOI: 10.1056/NEJMsa1603542. 
4Institute of Medicine (IOM). 2015. Sharing clinical trial data: Maximizing benefits, minimizing risk. Washington, DC: The National Academies Press.