> For the complete documentation index, see [llms.txt](https://docs.coupler.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.coupler.io/sources/category/other/castor-edc/data-overview.md).

# Data Overview

Castor EDC exposes a broad set of entities covering study structure, participant activity, user management, and compliance tracking. Here's a breakdown of what's available through Coupler.io.

## Entities overview

| Entity                   | What it contains                                        |
| ------------------------ | ------------------------------------------------------- |
| Users                    | User IDs, names, email addresses, account roles         |
| Studies                  | Study IDs, names, status, configuration metadata        |
| Audit trials             | Timestamps, user actions, field changes, record IDs     |
| Countries                | Country codes and names available in the system         |
| Study surveys            | Survey IDs, names, associated study, status             |
| Study survey packages    | Package IDs, included surveys, assignment details       |
| Study sites              | Site IDs, names, countries, status, study association   |
| Study fields             | Field IDs, types, labels, form association, options     |
| Study field dependencies | Parent field, dependent field, condition logic          |
| Study field validations  | Field ID, validation type, rule parameters              |
| Study forms              | Form IDs, names, type, associated study and phase       |
| Study roles              | Role IDs, names, permission sets                        |
| Study fieldoption groups | Group IDs, option labels, values                        |
| Study statistics         | Enrollment counts, completion rates, query metrics      |
| Study users              | User-study assignments, roles, access levels            |
| Study visits             | Visit IDs, names, scheduled dates, patient associations |

## Metrics and dimensions

#### Study statistics

| Metric                | Description                                      |
| --------------------- | ------------------------------------------------ |
| Enrolled participants | Total number of participants enrolled in a study |
| Completed records     | Count of fully completed data records            |
| Open queries          | Number of unresolved data queries                |
| Completion rate       | Percentage of forms or fields completed          |

#### Audit trail dimensions

| Dimension             | Description                            |
| --------------------- | -------------------------------------- |
| Timestamp             | Date and time of the logged action     |
| User                  | Who performed the action               |
| Action type           | Create, update, delete, or view        |
| Record ID             | The affected record or field           |
| Old value / New value | Before and after state of changed data |

#### Study visit dimensions

| Dimension  | Description                           |
| ---------- | ------------------------------------- |
| Visit name | Label for the scheduled visit         |
| Visit date | Scheduled or actual date of the visit |
| Site       | Site where the visit occurs           |
| Patient ID | Associated participant identifier     |

#### Study field dimensions

| Dimension        | Description                         |
| ---------------- | ----------------------------------- |
| Field type       | Text, numeric, date, dropdown, etc. |
| Field label      | Display name of the field           |
| Form association | Which form the field belongs to     |
| Required         | Whether the field is mandatory      |

## Common entity combinations

* **Study fields + Study field validations** — Join these to see every field alongside its validation rules. Useful for auditing data quality standards across a study.
* **Study users + Study roles** — Join to understand who has what access across your studies.
* **Study visits + Study sites** — Join to map visit activity by location, helpful for multi-site trial oversight.
* **Audit trials + Users** — Join to attribute every system change to a named user for compliance reporting.
* **Study statistics** — Use Aggregate to roll up enrollment and completion metrics across multiple studies.

## Use cases by role

{% tabs %}
{% tab title="Clinical data managers" %}

* Export **study fields** and **field validations** to document your data dictionary outside Castor EDC
* Pull **audit trails** regularly to maintain a compliance-ready log of all data changes
* Use **study statistics** to track form completion rates and open queries across active studies
  {% endtab %}

{% tab title="Research coordinators" %}

* Monitor **study visits** to track upcoming and completed patient appointments
* Combine **study sites** with visit data to compare activity across locations
* Export **study surveys** and **survey packages** to report on participant engagement
  {% endtab %}

{% tab title="IT and data engineers" %}

* Load all entities into **BigQuery** to build a centralized clinical data warehouse
* Use **Join** transformations to link users, roles, and study assignments in a single table
* Send **audit trail** data to **Looker Studio** for real-time compliance dashboards
* Pipe study statistics to **ChatGPT or Claude** to generate narrative study progress summaries
  {% endtab %}
  {% endtabs %}

## Platform-specific notes

* Castor EDC has three regional instances (UK, NL, US) — data is isolated per region, so your API credentials and exports only cover the region you registered in
* The **start date** parameter filters records by creation or modification date; without it, the full history is pulled on first run
* **Audit trials** can grow very large in long-running studies — setting a meaningful start date is especially important for this entity
* Study field dependencies and validations reflect the study design at the time of export; if you redesign a form, re-export to capture the updated structure
* The `study_fieldoption_groups` entity is only relevant for studies that use dropdown or multi-select fields


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