Microsoft's AI diagnostic system outperformed generalist physicians by more than two-to-one in a simulation involving complex medical cases, according to a study published Thursday in Science. Mustafa Suleyman, CEO of Microsoft AI, described the outcome as progress toward "medical superintelligence."

The system, called MAI-DxO (or DxO), orchestrates multiple AI agents that function like a panel of doctors—questioning a patient, ordering tests, and deliberating over a diagnosis. In simulations drawn from complex cases published in the New England Journal of Medicine, it reached 83% accuracy. Primary care doctors and general internists, working alone with reference materials, achieved 36%. One caveat: cases of this complexity are typically handled by specialists or physician teams, who were not included in the comparison. "The biggest challenge in healthcare delivery at the moment is the growing mismatch between demand and supply of medical expertise."

With these results, Microsoft aligns itself with Google and OpenAI in asserting that its AI can rival or exceed physician performance. The study's data indicates that much of the improvement stems from more capable underlying AI models, with Microsoft's orchestration layer contributing additional gains on top. Microsoft tested MAI-DxO using models from multiple companies—OpenAI, Google, Anthropic, Meta, and DeepSeek—but achieved its strongest results with OpenAI's GPT-5 and GPT-5.5.

Microsoft evaluated DxO on cost as well as accuracy, meaning the estimated expense of running the AI on each case. Used alone with a short, basic prompt, GPT-5 scored 78.9% on complex cases at roughly $8,400 per case. DxO reduced that cost by about $3,000 while improving accuracy by only about four points. On emergency department cases, neither accuracy nor cost showed much difference between GPT-5 alone and GPT-5 with DxO's assistance. With GPT-5.5, a newer model released in April 2026, the results diverged. On complex cases, DxO lifted GPT-5.5's accuracy from 72% to nearly 87% at a slightly lower cost. Yet again, the gains failed to materialize on emergency department cases—both configurations scored about 85% at similar cost. DxO delivers its greatest benefit on complex cases and with less capable AI models. Gemini 2.5 Flash, for instance, scored 46.4% alone but nearly 69% with DxO. Even so, the gap between weaker and stronger models exceeded the boost DxO provided. Microsoft's researchers noted that accuracy gains naturally diminish as models approach the theoretical ceiling. "The DxO orchestration helps with the broader challenge of optimization both accuracy and cost," a spokesperson added. He believes this approach will allow the company to "make really enormous leaps here," and says DxO forms part of the foundational infrastructure Microsoft is building to achieve real breakthroughs in healthcare. "I really believe that in 2027, we will be on the verge of a coding style breakthrough for medical records," Suleyman said. "I think we're going to be able to stream highly accurate predictions about how a medical record might unfold, and obviously that kind of foresight for a clinician is gold dust."

Suleyman has devoted his career to applying AI to medical challenges. He was previously a co-founder of DeepMind, which Google acquired in 2014. The following year, Google DeepMind acquired King's startup Hark, a clinical task management app, and the two launched DeepMind Health together. Suleyman joined Microsoft to lead its AI unit in 2024, and King followed a few months later. "We're just true believers," Suleyman said. He noted that while generative AI in healthcare remains early-stage, he expects healthcare models to become "an order of magnitude better in capability within the next 24 to 36 months."

"As we've seen multiple times in the last five or six years, the progress happens very quickly once you have a flywheel," Suleyman said. "A flywheel means we have a model in production which we are iterating with real world usage in order to identify gaps in the model and then patch them and improve them. That's what's happened in coding. It's what happened in chat before that. And I think next year it's going to start to happen for medical records and for clinical decision support."

Through a new partnership with Beth Israel Deaconess Medical Center in Boston, Microsoft will assess DxO's clinical reasoning capabilities across various hospital settings. "This technology is ready for real world evaluations, and you can imagine the complexity and diversity of issues that come from a Boston emergency department on a Friday evening," King said. He described how the study will operate: patients will receive standard treatment, including triage, time with a specialist, treatments, investigations, and a decision on whether discharge is safe. In parallel, those who consent will also interact with DxO. Microsoft and its partners will compare DxO's recommendations against those of human doctors. Google published a clinical study with Beth Israel in The Lancet this month evaluating Google's AMIE conversational diagnostic AI during real-world urgent care visits, with human physicians monitoring interactions in real time. "We think this will be the biggest study of its kind," King said. "It will be across not just emergency settings but urgent care environments, and will give us very compelling evidence by the end of the study period around the ability for these systems to be deployed at greater scale in the future."

Microsoft's study in Science coincides with something of a manifesto outlining what it will take to build medical superintelligence, defined as "the capacity to surpass the strongest contemporary human-led health systems in medical reasoning and coordination across the full arc of care." Microsoft aims to move beyond benchmarking individual tasks—such as answering medical exam questions and generating diagnoses—toward integrating with clinicians and healthcare systems for improved outcomes. "This is the kind of technology that everybody in the world wants, and that's why we're committed to doing everything we can to accelerate its introduction to the world," Suleyman said, adding that this focus could differentiate Microsoft from other frontier labs. Microsoft already sells dictation and radiology tools to clinicians and views DxO as an expansion of those efforts. "We have to have the absolute number one state-of-the-art medical clinical decision support products over the next few years," Suleyman said.