Updates to trial information: a review of activity on the ANZCTR
We do not currently know how often trial information is updated globally. Using the information on the ANZCTR, this review explored:
The number of times trial registrations are updated,
When updates occur,
What information is updated, and
What types of trials update their information.
This review uses information from clinical trials registered from 1 January 2015 to 31 May 2024 on the ANZCTR.
How often is trial information updated?
63% of trials update their information at least once during their life cycle (i.e. 8,150 updated trials out of 13,018 trials total)
On average, trials revise their records twice, with most updating one to three times – see Figure 1
Note: graph contains information for 8,150 updated trials.
Figure 1. Number of updates completed per trial.
When is information updated?
Most updates occur about 12 months after trial registration
This aligns with the ANZCTR’s automated reminder email sent at 11 months, prompting investigators to update their records – see Figure 2
Figure 2. Number of months to first update.
What information is updated?
Trial sponsors most often update recruitment-related details – see Figure 3. These include:
Recruitment dates
Sample size (how many participants they plan to recruit, or the number they actually recruit)
Recruitment status (for example, whether recruitment is ongoing, closed but still in follow-up, or completed)
Note: The ANZCTR collects information for over 130 fields. These fields were reviewed and grouped into broad categories developed and agreed by ANZCTR Staff. Graph is limited to top 15 categories.
Figure 3. Types of updates made by number of trials.
Which trials update their records?
Trials are more likely to have updated information if they were registered with the ANZCTR five or more years ago, include randomisation, or have any industry involvement (Table 1).
Table 1. General characteristics of updated trials.
Characteristic | Number of trials updated at least once (% of total trials) |
Year registered | |
2015 | 891 (74.3%) |
2016 | 1,056 (72.5%) |
2017 | 1,013 (72.5%) |
2018 | 1,198 (69.9%) |
2019 | 1,003 (67.0%) |
2020 | 656 (58.8%) |
2021 | 970 (65.4%) |
2022 | 789 (58.3%) |
2023 | 613 (43.1%) |
2024* | 61 (9.9%) |
Trial design | |
Randomised controlled trial | 5,863 (64.8%) |
Non-randomised trial | 2,287 (57.9%) |
Industry involvement** | |
Any industry involvement | 1,422 (75.0%) |
No industry involvement | 6,993 (56.9%) |
*Includes information up to 31 May 2024
**Industry involvement includes studies where a company is involved as a sponsor, funder or collaborator.
What happens next?
The ANZCTR will:
continue education on the importance of keeping trial information up to date – for example, this information is reused by public-facing websites, apps for medical doctors, and trial recruitment services,
continue encouraging updates to trial information annually through reminder emails,
consider tailoring reminders to align with key trial milestones (e.g. expected recruitment end dates), and
explore ways to simplify the update process, such as automated approvals of updated information.