Ada Health Clinical AI Turns Symptom Uncertainty Into Appropriate Action, Finds NEJM AI Study Conducted with CUF in Portugal

Real-world study at CUF, Portugal's largest private healthcare network: Ada's accurate, medical-grade assessment changed the behavior of 3 in 5 patients — and more than doubled the proportion receiving clinically appropriate care

BERLIN, April 22, 2026 /PRNewswire/ -- Ada Health, a leading clinical AI company that helps people understand their symptoms and navigate care safely and efficiently, today announced the publication of a landmark study in NEJM AI, the AI journal of the New England Journal of Medicine, demonstrating that CUF Hospitais & Clínicas patients who use Ada make measurably better decisions about where and how to seek care.

When people experience unexplained symptoms, navigating to the right care is rarely straightforward. Uncertainty about whether to see a primary care physician, a specialist, or seek emergency care can lead to delays, missed diagnoses, and in some cases years spent in the wrong part of the health system. AI-powered tools have increasingly been deployed to help address this problem, but most evaluations have focused narrowly on vignettes, algorithm accuracy, or stated patient intent, offering little insight into whether patients actually change their behavior, or whether the care they receive is clinically appropriate.

The ESSENCE study, conducted in partnership with CUF, Portugal's largest private healthcare network, was designed to close that gap. Prospective in design, with electronic health record linkage, follow-up surveys, and an independent physician panel rating the appropriateness of both intended and observed care, it goes beyond curated test sets and hypothetical cases to capture what actual patients do in the real world. When Ada's behavior-changing clinical intelligence is made available to patients, it allows them to act immediately, driving measurable improvements in the quality of care-seeking decisions.

"For too long, the conversation about AI in healthcare has focused only on accuracy scores and theoretical potential. This study changes that. It shows that when Ada is embedded into a real patient care journey it doesn't just inform them, it transforms how they navigate care. That's the standard we should hold digital health tools to."

— Dr. Fabienne Cotte, First Author and Ada Health Clinical Studies Advisor

From Intent to Appropriate Action: What the Data Shows

The study enrolled 1,470 adults through myCUF, CUF's patient app combining symptom assessment with direct care booking. Among those, the study found:

• Changes in what patients intended to do: 1 in 3 revised their intended care level immediately after their Ada assessment, with the proportion reporting "I'm not sure what to do" falling from 12.6% to 5%.
• What patients actually did: When care was tracked through electronic health records and follow-up surveys in the weeks that followed, nearly 3 in 5 attended a different care setting than originally planned.
• Whether it was the right care: Appropriate care more than doubled — from 29.8% to 64.4% — with physician review confirming that patients sought the most appropriate level of care after using Ada to support their decision-making. Among patients who had originally planned to visit an emergency department, nearly 40% ultimately chose a lower acuity setting rated as appropriate by the physician panel. Subsequent emergency visits and hospitalisations were tracked through electronic health records, with no concerning safety signals identified.

"Innovation in healthcare must go beyond promise and demonstrate real-world value. This study does that. When patients receive accurate, clinical guidance at the moment of uncertainty and can act on it immediately, the evidence is clear: they navigate to the right care. That has real consequences for real people."

— Dr. Micaela Seemann Monteiro, MD, Chief Medical Officer for Digital Transformation, CUF

Activating Appropriate Action

The central finding of this study is that patients changed their behavior, rather than just their intentions. Additionally, patients were activated and connected to the right services and bookable actions upon completing an Ada assessment. Instead of simply reducing demand, patients were redirected to the appropriate care setting. For too long, digital health has been measured by engagement. This study sets a new bar for what AI in healthcare should be held to: not accuracy scores and not stated intent, but outcomes.

About the Study

"From Advice to Action: Real-World Behavior of Patients Using an Integrated Diagnostic Decision Support System for Navigating the Healthcare System" by Cotte et al. is published in NEJM AI (April 2026 issue). The study is observational in design; observed associations reflect the combined effect of Ada's assessment and the availability of bookable services within CUF's myCUF platform.

About Ada Health

Ada Health combines clinical expertise and advanced AI to help people and health organizations act on insights earlier. Built by doctors, scientists, and engineers, Ada applies probabilistic reasoning technology to a medical expert-curated knowledge base that transforms real-world data into actionable guidance, empowering individuals to understand their symptoms and helping partners across healthcare and life sciences deliver more timely, personalized care. As a Class IIa medical device under the EU's Medical Device Regulation (MDR) with over 40 million assessments completed and 50+ independent and peer reviewed publications, Ada's technology is trusted by leading health systems, insurers, and pharmaceutical companies to improve outcomes, streamline care pathways, and build a smarter, more connected future of health. Learn more at about.ada.com.

About CUF

With more than eight decades of experience, CUF leads private healthcare in Portugal, with an integrated network of 66 hospitals, clinics and health centres, as well as homecare services and digital channels. Through the daily dedication of more than 16,000 employees, CUF is recognized for its clinical excellence, innovation, and strong values that support the delivery of high-quality healthcare.

For 40 years dedicated to the diagnosis and treatment of cancer, it is today the largest private provider of oncology diagnostics in Portugal and the third-largest diagnostic provider nationwide. CUF Oncologia ensures a close and compassionate approach to the prevention, diagnosis and treatment of cancer, as well as follow-up care after oncological treatments.

CUF is the most trusted and recognized healthcare brand in Portugal, serving more than 14% of the Portuguese population across the country. CUF acts consistently to create positive impact, contributing to the building of a sustainable and innovative future. Learn more at cuf.pt   

Media Contact

Shireen Saxena
VP External Affairs and Chief of Staff, Ada Health
[email protected]

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SOURCE Ada Health