Feature Extensions

Filter by Subset of Participants

Lasso allows you to narrow your query results to only the participants you care about — whether they were part of a specific sub-study, used in a published paper, or flagged for follow-up. 

You can do this by uploading a list of participant IDs using our Participant Subset Filter tool. 

Common Use Cases

This feature is especially helpful when: 

  • You want to analyze data only for participants who were in a sub-study. 
  • You're reproducing a published analysis that used a specific cohort. 
  • You're revisiting a flagged participant list for data quality checks or outliers. 
  • You’ve received a list of participants from a collaborator and want to limit the dataset accordingly. 

How to Use the Filter

  1. ‍Look for the Button

‍On supported tools (e.g., All Study File-Based Data, Query Wizard, and Dictionary Query Tool), you’ll see a purple button labeled: FILTER FOR A SUBSET OF PARTICIPANTS. This button is only visible if you’ve completed training and have an active Data Use Certificate.

  1. ‍Click to Open the Filter Tool
    ‍    A popup will appear with two options:
    1. ‍Download the CSV Template 
      Click this to download a file in the correct format. It contains a single column: participant_id
    2. ‍Upload Your CSV‍
      Upload a CSV with the participant IDs you'd like to filter by. You can either:
      • Use the template you downloaded, or
      • Upload your own CSV as long as it has a participant_id column. ‍
  1. ‍Apply and View Results
    ‍    Once uploaded:
    A success message will confirm how many participants matched.

You’re now viewing only data for those participants — across all their visits.

  1. ‍Clear the Filter
    ‍    To remove the filter, click the ✖ on the button. Your results will return to showing all participants. 

Errors You Might See

When uploading a participant filter file, you may encounter one of the following messages. Each is designed to help you quickly identify and resolve formatting or content issues.

File Isn’t a CSV

Message:
Unsupported filetype

What it Means:
The file must be in .csv format. Other formats (like .xls, .xlsx, .txt) are not supported.

What to Do:
Download the correct template from the Upload Participant Filter dialog and ensure you're saving and uploading a .csv file.

File Is Empty or Missing IDs

Message:
File is empty

What it Means:
The file contains rows without valid data

What to Do:
Double-check that you’ve entered at least one valid participant ID under the correct header. You can always re-download the template to ensure the format is correct.

Incorrect File Structure

Message Displayed:
Missing the participant_id column.

What It Means:
The uploaded file does not contain the required column named participant_id, which is essential for filtering participants.

What to Do:

  • Make sure your CSV file includes a column header exactly labeled: participant_id (case-sensitive, no spaces or typos).
  • If you're unsure, download the template CSV using the Download Template CSV button provided in the modal.
  • Open the file in Excel, Google Sheets, or your preferred CSV editor, and double-check the header row.

Duplicate IDs Detected

Message:
Duplicate participant_ids found, only [X] participants found

What it Means:
Your file includes duplicate participant_id values. To ensure accurate filtering, the system automatically removes duplicate entries and proceeds using only unique participants.

What to Do:
No action is required unless duplicates were unintentional. You can continue filtering with the number of participants shown. If needed, remove duplicates in Excel or your CSV tool and re-upload.

What the Filter Affects

  • Applies only to the query tool or tab you’re working in. 
  • Stays active while you’re in that tab. 
  • Does not persist if you log out or refresh the page. 
  • Filtered results will reflect in downloads and exports. 

Confirmation 

  • A success message will appear upon upload, showing how many participants were recognized and filtered into your query.
  • A label or visual indicator confirms that the participant filter is active. 

Output Behavior 

  • ‍Tabular queries return only filtered results. ‍
  • File-based downloads are limited to filtered participants. 
  • A Shadow Matrix is still generated to assess missingness. 

Persistence and Scope 

  • The filter is session-specific and must be re-applied after logout. 
  • Only users with DUC approval and training completion can apply and execute filtered queries.