Project Summary

This research project is in progress. PCORI will post the research findings on this page within 90 days after the results are final. In the meantime, results have been published in peer-reviewed journals, as listed below.

What is the research about?

Researchers can use a study design called an N-of-1 trial to learn how well a treatment works for a specific patient. These trials include only one patient and compare the time when a patient is getting treatment to the time when he or she is not.  Researchers can also combine multiple N-of-1 trials to look at treatment effects across patients.

Although N-of-1 trials show promise, researchers rarely use them. Many researchers aren’t familiar with the methods. Also, researchers don’t have an easy way to collect and analyze data from these studies.

In this study, the research team is tailoring a mobile app called Eureka and using it to conduct N-of-1 trials. Eureka allows the research team to collect and track patient data and view results from these trials. The trials focus on inflammatory bowel disease, or IBD, in children and atrial fibrillation, or AF, in adults. The team chose IBD and AF because N-of-1 studies are most useful when symptoms and response to treatment vary widely across patients, as is the case with IBD and AF.

This study has three parts:

In Part 1, the research team is using a series of N-of-1 trials to see how well the specific carbohydrate diet, or SCD, reduces symptoms and inflammation in children with IBD compared with a modified SCD.

In Part 2, the team wants to know if using an N-of-1 study design helps patients identify and avoid AF triggers and episodes compared with tracking symptoms without the structure of an N-of-1 trial.

In Part 3, the team is examining study participants’ views on the feasibility and acceptability of N-of-1 designs.

Who can this research help?

Results from this research may help patients and clinicians considering management options for IBD and AF. This study may also help researchers learn more about the feasibility of using N-of-1 trials for comparing treatments.

What is the research team doing?

The research team is recruiting 120 children with IBD and 478 adults with AF. 

In Part 1 of the study, participants with IBD are beginning the trial on their usual diet. They then alternate between the SCD and a modified SCD for 32 weeks. Using the Eureka app, patients report daily on stool frequency and weekly on pain and other symptoms. They also mail stool samples for analysis throughout the study. At the end of the N-of-1 study, patients receive results about the diet’s effects on their symptoms and inflammation. The research team is also combining results of individual N-of-1 trials to see the effects across patients.  

In Part 2, the research team is assigning patients by chance to one of two groups. All patients receive text reminders to track their AF episodes, triggers, mood, and sleep quality in the Eureka app. Patients in both groups can also see a summary of their symptoms and triggers over time. One group follows the N-of-1 design. In that group, patients choose one thing they think triggers AF, like caffeine. Then they track what happens when they have caffeine or don’t. At the end of the study, they receive a report on whether that trigger is related to their AF. In the second group, patients track symptoms in the app without this design. After 3 months, the team is comparing quality of life and AF severity for patients in the two groups.

In Part 3, the research team is interviewing patients who completed N-of-1 trials as part of the IBD or AF study to understand their experiences with N-of-1 trials.

Patients with AF and IBD, parents of children with IBD, clinicians, and researchers helped develop and prioritize the research questions. The research team also includes patients with AF and IBD and parents of children with IBD, who are helping to plan and carry out the study.

Research methods at a glance

Design Elements Description
  • Use a series of N-of-1 trials to determine the effectiveness of the SCD in reducing symptoms and inflammation in patients with IBD as compared to a modified SCD and a usual diet.
  • Compare the effectiveness of using N-of-1 designs versus data tracking alone to help patients identify and remove AF triggers and reduce AF severity.  
  • Assess the feasibility and acceptability of using the N-of-1 study design in children with IBD and adults with AF.
  • N-of-1 trials
  • Mixed methods

Project Information

Heather Kaplan, MD, MS
Cincinnati Children’s Hospital Medical Center
Using Single Subject (N-of-1) Designs to Answer Patient-Identified Research Questions

Key Dates

August 2016
June 2022

Study Registration Information


Has Results
Health Conditions Health Conditions These are the broad terms we use to categorize our funded research studies; specific diseases or conditions are included within the appropriate larger category. Note: not all of our funded projects focus on a single disease or condition; some touch on multiple diseases or conditions, research methods, or broader health system interventions. Such projects won’t be listed by a primary disease/condition and so won’t appear if you use this filter tool to find them. View Glossary
Populations Populations PCORI is interested in research that seeks to better understand how different clinical and health system options work for different people. These populations are frequently studied in our portfolio or identified as being of interest by our stakeholders. View Glossary
Intervention Strategy Intervention Strategies PCORI funds comparative clinical effectiveness research (CER) studies that compare two or more options or approaches to health care, or that compare different ways of delivering or receiving care. View Glossary
State State The state where the project originates, or where the primary institution or organization is located. View Glossary
Last updated: April 20, 2022