Most national regulations require that the data from a clinical trial be archived and available for a number of years after the trial's completion. That number of years varies by country. This means that the clinical trial needs to have an archival strategy.
When using an EDC system, it is also important to archive the meta-data used during the trial. Meta-data includes information about the eCRFs, the questions, and the validation logic. The meta-data plays a critical role in understanding how data was collected and handled during the study.
An obvious choice of format for archiving is the CDISC Operational Data Model (ODM). This is a de facto standard for representing clinical trial data in XML. The advantage of using this is that one would expect that in five or ten years' time there will be a company out there with a viewer for ODM that will allow a regulator or auditer to look at the ODM trial data in a usable way. This is the advantage of a standard - if the standard is adopted, which ODM is, a market emerges to support it.
Of course, an ODM viewer is only the starting point. What is really needed is an ODM Navigator that allows the user to query the data to extract subsets, to understand trends, and to look at data on a site by site basis.
However, ODM has important weaknesses as well that you need to be aware of. Of course, these may be addressed in future iterations of the standard.
The first is that it is not good at representing logic. Therefore any complex validation logic, calculations, and notifications will be difficult to capture in ODM format. That information can be critical for understanding what happened in a clinical trial many years from now.
Status information is also not so straight forward to represent. For example, whether a patient is withdrawn, excluded, lost to follow-up, and so on.
A second, and perhaps more critical issue, is that to be able to truly recreate a trial at any point it is necessary to maintain site specific snapshots of its meta-data and its data. Conceptually, this means that each site would need to have an ODM export before any change was made to the data.
As I mentioned in another posting, not all sites will be ready to adopt a protocol amendment at the same time: each site may be using a different version of the eCRFs at any one point.
Let's imagine we have two sites, A and B. Because they can get ethics approvals at different times, site A is able to deploy a protocol amendment before site B. We will denote the eCRFs before the amendment as v1 and those after as v2. To archive this data we will have four snapshots: site A with v1 data, site A with v2 data, site B with v1 data, and site B with v2 data. The archive must distinguish among these four snapshots.
When examining an archiving solution, make sure that it can address this issue. Such a capability will save a lot of agony later on.
Although I did not discuss it here, audit trails also need to be part of the archive. They will also have the same versioning issue discussed above.