Study management

Create a study

  1. Click on Create new study

  2. Fill in all required fields on the page:

    • Name describes the title of the study you want to create

    • Principal Investigator is the lead researcher

    • Responsible contact person is the person who can be contacted if any questions regarding the study occur

    • Phone number and E-mail-address are the contact information at which the contact person can be reached

    • Required number of subjects is the number of people you need to recruit for this study

  3. Decide on setting it up as a regular study that includes study recruitment and execution or as a one time invitation. The option Is a one time invitation should only be used when you are sure that it is sufficient to invite potential subjects anonymously via mail.

  4. Fill in any additional information (you can still do that later)


    Quick note on Consent: this allows users to upload a blueprint of the study consent. This blueprint can be obtained (and printed) later by recruiters or conductors.

  5. Click on Save to record your progress


When choosing option Is a one time invitation: Please be aware that Castellum will not track actual participations or appointments and it will not provide pseudonyms within the study.

Now you can find your study in the studies list.

Set up sessions

In the Sessions tab, you can enter as many test sessions as you like.

  • Add session

  • Set up Start of test sessions and End of test sessions

  • Define general Session instructions


In Session Instructions you can inform recruiters on conditions/requirements that may be important for or in between sessions. For example, recruiters are often asked to ensure a certain time interval between session appointments. This would be explained here.

Start and End of test sessions allows Castellum to offer an approximate overview schedule of all studies in Calendar view at Study management.

When adding a test session:

  • Always give the session a Name and specify the Duration of a session in minutes (duration will be used for appointment booking)

  • Additionally, select the Type of the session and (if applicable at your institute) select Resources

  • Additional text for reminder emails allows you to provide information to subjects prior to the actual appointment. You can send yourself a test mail to check the appearance of session reminders by using the corresponding button

  • If your institute uses the external scheduler to schedule appointments, you can enable it here (see Set up an external scheduler for appointments)

For existing sessions a Delete button allows you to delete any test session you created. Click on Update to review or edit session details.

Set up the recruitment process

Castellum offers three features to restrict which subjects are considered for your study:

  • Attribute filters

  • Excluded studies

  • Text based inclusion and exclusion criteria as part of the recruitment text

  1. Go to the Recruitment Settings tab

  2. By clicking on General the Recruitment text will be shown to you. You can:

    • edit the Recruitment text (this text will be shown to recruiters and will be used by them to recruit subjects for your study). Use this for text based inclusion and exclusion criteria when there is no data available in Castellum that you could use for an attribute filter

    • decide whether you wish to set up the Advanced filtering (this allows you to create multiple filtergroups that are not linked to each other),

    • set the function Exclusive subjects (If you select this feature, potential subjects for your study cannot be recruited for other studies. Please note that this may prevent other researchers from finding enough participants.) and

    • decide whether Complete filter matches only will be shown to the recruiters of your study or if there will be some subjects displayed, in which certain characteristics still have to be queried


    Session types may come with specific criteria that have to be checked every time before appointing subjects to a session. In this case, you’ll see a caret with a label Criteria for: <type> next to the recruitment text. Clicking on it will show you the text that is always appended. In other words: You don’t have to write this type specific text by yourself.

  3. By clicking on Filter you are able to set filter criteria

    • select the attribute that should be used for filtering

    • click Add

    • define the filter

    • click Apply

    You may set as many filters as you like.


    Please note that all filter criteria set up within this filter group have to be fulfilled. This also means that opposing filters would result in an empty set.

    Sometimes you need to define more than one mutually exclusive group of suitable subjects. For this, you have to set up advanced filtering in general recruitment settings to create various filter groups.

    Subsequently, when you click on Add new in Filters, you are able to set another filter group with specific filters. Alternatively, you could duplicate an existing filter group and edit it afterwards.


    This is necessary if you need subjects both at the age between 20-30 and 50-60. Again, note the distinction between Any of these and All of these.

  4. In Excluded studies you can select certain studies in which your subjects must not have participated

  5. To allow recruiters to send batch invitations via e-mail, proceed as follows:

    • click on Mail Settings

    • define an E-mail subject

    • add an E-mail body

    This e-mail will be sent by recruiters at study recruitment by specifying the amount of recipients. Yet, you can check the appearance of the set up mail by sending a test mail to yourself with corresponding button.


    It is not intended to send e-mail attachments via Castellum. Instead, links can be inserted as standard text.

Create a geo filter

If that feature has been activated on the server, Castellum also allows to filter by geographical properties of a subject’s address.


If the desired participants for a study should be older than 40 years and live in an area where the noise from an airport is over 40dB you would create and upload a GeoJSON file with a (multi)polygon spanning the area where this condition applies. Afterwards proceed as usual with setting the filter for age in the study filter UI. The resulting subjects in the recruitment interface match the filter condition AND their contact address is located inside the uploaded polygon.

GeoJSON format

To use this, you need to provide a valid GeoJSON file with a either a single feature or a feature collection of type “Polygon” or “MultiPolygon”. Castellum will then filter all subjects that live inside this (multi)polygon, so it should enclose all areas where the conditions for recruitment are met. Note that the Coordinate Reference System (CRS) must be WGS84 (EPSG:4326).

This is an example of a valid GeoJSON file:

  "type": "Feature",
  "properties": {},
  "geometry": {
    "type": "Polygon",
    "coordinates": [[
      [13.3517429, 52.5189382],
      [13.2908489, 52.5165476],
      [13.3463410, 52.4848593],
      [13.3512518, 52.4468630],
      [13.3964313, 52.4785787],
      [13.4627272, 52.4504546],
      [13.4308069, 52.4893448],
      [13.4730399, 52.5192370],
      [13.4141102, 52.5180417],
      [13.3821899, 52.5604549],
      [13.3517429, 52.5189382]
} is a simple tool to preview and edit GeoJSON.

How to convert a shapefile to GeoJSON

Most Geographic Information Systems (GIS) such as QGIS or ArcGIS support the conversion to GeoJSON out of the box. Desktop GIS applications should automatically reproject the shapefile to WGS84 during the export to GeoJSON format.

How to optimize GeoJSON for performance

The duration of the calculation scales roughly linearly to the number of vertices in the GeoJSON file. If the calculation takes too long, try to reduce the number of vertices in the file. This can be achieved in two ways:

  • Crop the spatial extent of your geographic data to the extent of the area where the subjects live (or at least most of them). This makes sense if most of your subjects are from the same city or state.

  • Generalize your polygon. This reduces the amount of vertices while retaining the general shape of the polygon. This makes sense of the resolution of your data is very high. Remember that Castellum derives the subjects’ geolocations from their addresses, which refer to houses. Therefore, a polygon with a resolution of 10cm has no advantage over one with a resolution of 10m, as address data is resolved to 10m at best, as determined by typical house sizes.

Manage study pseudonym lists

In the Pseudonym lists tab you can create, rename, and delete pseudonym lists.

If there are general lists, you can also define which general pseudonym lists need to be accessed in the context of this study.

Manage study members

The Member management tab allows you to give other staff members (e.g. recruiters) access to your study. Each row of the table represents a member. You can change their groups or remove them from your study. The last row allows you to add new members to the study.


Some features (e.g. recruitment) only become available once the study is started. So, some added users may not instantly notice those role changes.

Start and stop a study

After a study has been created it is still in a draft state. Only Study Approvers have the permission to start recruitment. Depending on your organization, there may be different organizational steps such as a review associated with that.

In order to start or stop a study, a Study Approver needs to follow these steps:

  1. Find the study at the Studies page, click Details next to the study you wish to start/stop

  2. You can find the button Start near to the study name. By clicking on Start you initiate the recruiting process. Started studies will offer a stop button instead to stop (or pause) recruitment.


A study can still be changed after it has been approved and started. The tab “Changes” provides an overview of all the settings for a study. Any changes that were made since the study was started are highlighted.

Finish a study

  1. Find the study at the Studies page, click Details next to the study you wish to finish/resume.

  2. You can find the button Finish study next to the study name near to other buttons.


All information related to potential subjects who were not participating in the study will be deleted when the study is finished. Hence, if you finish and then resume a study, it is possible that subjects that were already found to be unsuitable are suggested again as potential subjects.

Delete pseudonym lists

The date when a pseudonym list should be deleted (effectively anonymizing the research data) is usually defined in the ethics application and the study consent form.

Once you delete a pseudonym list from Castellum it is no longer possible to answer export or delete requests. Make sure that all relevant external data has been deleted before you delete a pseudonym list from Castellum. Then proceed as follows:

  1. Find the study at the Studies page, click Details

  2. Go to the Pseudonym lists tab.

  3. Find the relevant pseudonym list and click Delete.

  4. Follow the instructions to confirm the deletion.

Delete a study

When a whole study should be deleted depends on the rules of your specific organization. We assume that it makes sense to delete all study data after few years.

  1. Find the study at the Studies page, click Details

  2. Make sure the study is finished (see Finish a study)

  3. Click on Delete under the study name. Confirm the notice I have made sure that all external data related to this study has been destroyed by clicking on Confirm

Find your study

Click on Studies on the front page

  • In the field Search you can look for a certain study

  • By selecting Mine in Membership, you will see studies you created or are a member of. Under the field All you can see all studies that have been created.

  • By choosing a Status and / or a Study Type, you may also filter studies

Check whether the database contains enough subjects for your reasearch project

Click on Studies on the front page and then on Try filters. You can now experiment with filters just as in a regular study. The preview will show you how many subjects in the database match your filters.


By the time of writing (September 2021) the MPI for Human Development recommends its Castellum recruiters to aim for at least 10× more potential than required subjects for a smooth recruitment process. Otherwise it becomes essential to populate the database via external sources or efforts first.

If you decide you want to keep the set of filters you can go to Convert to study to convert your temporary settings to a regular study.