Project Summary

PCORI has identified the need for large studies that look at real-life questions facing diverse patients, caregivers, and clinicians. In 2014, PCORI launched the Pragmatic Clinical Studies initiative to support large-scale comparative effectiveness studies focusing on everyday care for a wide range of patients. The Pragmatic Clinical Studies initiative funded this research project.

This research project is in progress. PCORI will post the research findings on this page within 90 days after the results are final.

What is the research about?

Mycobacterium avium complex, or MAC, is a type of bacteria that exists in water, soil, and dust. Most people don’t get sick from MAC bacteria. But older adults, people with immune systems that don’t work well, and those with lung disease have an increased risk of MAC infections. MAC infections most commonly affect the lungs, and symptoms include shortness of breath, fever, and fatigue. Treatment involves taking multiple types of antibiotics for 18 to 24 months. These antibiotics can have side effects such as nausea and diarrhea. The infection’s symptoms and treatment side effects can decrease patients’ quality of life.

In this study, the research team is comparing the effects of treating MAC infection with two versus three different antibiotics. The team wants to know whether treatment with two different antibiotics is as effective as and better tolerated than treatment with three.

Who can this research help?

Results may help patients and doctors when considering how to treat MAC lung infections.

What is the research team doing?

The research team is enrolling 500 adults with MAC lung infections at 26 U.S. and Canadian sites in the study and assigning them by chance to receive treatment with either two or three different antibiotics. All patients receive standard care from their doctors.

The research team is reviewing health records and collecting clinical data for the first 12 months of treatment to see how many patients

  • No longer have an infection
  • Finish 12 months of treatment
  • Develop resistance to the antibiotics

Five times during the study period, the research team is surveying patients about their symptoms, treatment side effects, and quality of life. The team is comparing outcomes between patients who take two antibiotics and those who take three.

Patients, patient advocates, and clinicians are providing input on the design, outcomes, and recruitment for the study.

Research methods at a glance

Design Elements Description
Design Randomized controlled trial
Population 500 adults ages 18 and older with pulmonary MAC disease
  • 2-drug regimen (azithromycin and ethambutol)
  • 3-drug regimen (azithromycin, ethambutol, and rifampin)

Primary: acid-fast bacilli culture negativity, therapy completion with satisfactory adherence (defined as taking 80% of prescribed doses or not missing more than 75 days of treatment taken three times per week)

Secondary: respiratory symptoms, quality of life, fatigue, gastrointestinal symptoms, liver function, macrolide resistance

Timeframe 1-year follow-up for primary outcomes

Project Information

Kevin Winthrop, MD, MPH
Oregon Health & Science University
Multicenter Randomized Pragmatic Clinical Trial Comparing Two- versus Three-Antibiotic Therapy for Pulmonary Mycobacterium Avium Complex Disease

Key Dates

April 2018
September 2026

Study Registration Information


Award Type
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: January 20, 2023