Microsoft's AI beats doctors on complex diagnoses in a simulation, study finds
Microsoft's MAI-DxO system correctly diagnosed 83% of complex medical cases in a simulation, against 36% for generalist doctors. Microsoft AI CEO Mustafa Suleyman calls it a step toward "medical superintelligence".
An AI diagnostic system built by technology company Microsoft identified complex medical conditions more than twice as often as generalist physicians in a simulation. The study was published Thursday in the journal Science. Mustafa Suleyman, CEO of Microsoft AI, called the result a step toward "medical superintelligence", although the study's own data suggests much of the gain comes from more powerful underlying AI models.
How the system works
The system, named MAI-DxO (DxO for short), coordinates several AI agents that act like a panel of doctors: they question a patient, order tests and debate a diagnosis. The simulation used complex cases from the New England Journal of Medicine. DxO was correct 83% of the time, while primary care doctors and general internists working individually with reference materials were correct 36% of the time. Cases this complex are usually handled by specialists or physician teams, who were not part of the comparison.
The role of the models
Microsoft tested DxO with models from OpenAI, Google, Anthropic, Meta and DeepSeek; the best results came with OpenAI's GPT-5 and GPT-5.5. GPT-5 alone scored 78.9% with a short, basic prompt, and DxO cut the cost by about $3,000 per case while raising accuracy by only about four points. With GPT-5.5, accuracy on complex cases rose from 72% to nearly 87%. On emergency department cases there was little improvement. For the weaker Gemini 2.5 Flash, the score rose from 46.4% to nearly 69%.
What comes next
Suleyman said Microsoft is working with Mayo Clinic on a foundation model for healthcare, planned for release next year. Through a partnership with Beth Israel Deaconess Medical Center in Boston, DxO will be evaluated in real hospital settings: patients will receive standard care, and those who consent will also interact with DxO, whose recommendations will be compared with the doctors'. Google also published a clinical study of its AMIE diagnostic AI in The Lancet this month.
Microsoft already sells dictation and radiology tools to clinicians and sees DxO as an expansion of those efforts.
