Microsoft’s AI diagnostic system, MAI-DxO, correctly diagnosed complex medical cases 83% of the time in a simulation, compared to 36% for generalist physicians, according to a study published in Science. The system uses several AI agents working together, and its best results came with OpenAI’s GPT-5 and GPT-5.5 models. Microsoft claims DxO is most effective on complex cases and with less capable models, but gains are smaller as models improve.
The study measured both accuracy and estimated cost per case. DxO improved accuracy and reduced costs when paired with certain models, but showed little benefit in emergency department cases. Microsoft is now working with the Mayo Clinic to train a healthcare foundation model, aiming for release next year, and will evaluate DxO’s clinical reasoning at Beth Israel Deaconess Medical Center. Google is running a similar trial with its AMIE diagnostic AI.
For healthcare and pharma leaders, this signals accelerating AI capability in diagnostics and clinical support. Real-world hospital trials will test whether these systems can deliver reliable results outside simulations. The results may influence future investment and regulatory scrutiny in digital health.
