His research and teaching focus on patient outcomes and quality of care.
He was among the first to measure quality of life outcomes in people with HIV. He co-founded the Outcomes Committee of the AIDS Clinical Trials Group of the NIH ACTG. He developed the MOS-HIV Health Survey, a leading measure of health related quality of life for people with HIV that is used widely in international trials and research studies.
He has studied the handling of medical errors since 1988, and has published influential papers including “Do house officers learn from their mistakes” (JAMA 1991), “Medical error: the second victim” (BMJ, 2000). He was a member of the Institute of Medicine committee on Preventing Medication Errors, and Senior Adviser to the World Health Organization Patient Safety program in Geneva from 2007-2009. He leads the Armstrong Institute center for meaningful measures
He was director of the AHRQ-funded Hopkins DEcIDE center for comparative effectiveness research from 2005-2013. He is Director of the Center for Health Services and Outcomes Research (CHSOR), the online Masters of Applied Science in Patient Safety and Healthcare Quality, and is Editor in Chief of Journal of Patient Safety and Risk Management (Sage)