Tools for the diagnostic problem we can't solve alone.

We've known for decades that educating patients and sharing decisions improves outcomes. We've also known it eats time. That tension is old.

What's new is generative AI. Patients now arrive misinformed and anxious, with details in hand that make us look uninformed — and that often force unwise use of resources and treatments.

I built TerrainDx as a doctor living the same experience, wondering if we could regain control of the narrative. Could we give patients an understanding of their diagnostic possibilities in a way that actually helps us take care of them?

For many patients, I think the answer is yes.

Sharing the 70 diagnoses that could explain their symptoms gives the patient a sense of the overwhelming probability that those symptoms are benign — and that we have the time to work through options sensibly. More importantly, in our testing the AI surfaces details of the history that help point the patient in the right direction and help us reach a diagnosis. It does surface zebras, but it explains the risk factors and time patterns that lead there, past the many more common alternatives. For the few scary diagnoses, or ones that progress rapidly, it points out the signs of progression that signal the need for quicker evaluation. This may be especially useful for the patient who previously would have come to us demanding specific testing well before their pretest probability made that testing meaningful.

One of the design journeys I most valued was the question that produced "the wider view" lake — the unknown node on every map.

Even with 70 diagnoses on the list, what's the chance the real one isn't?

Clinically, I know I typically underestimated it, and I'd never have put it on the table with a patient. I found some guidance in the ecology literature. The math used to estimate species in a forest after a brief survey by ten grad students turns out to share many properties with estimating how many diagnoses ten AI agents missed in a patient history. Most of the unknown comes from parts of the story that are wrong or left out. Some comes from misunderstood science. Some isn't yet known to science.

Having the unknown on the table — 10%, 30%, 50% — takes the pressure off. It also emphasizes what we're actually good at: looking at a well-organized array of diagnoses and intuiting which need immediate attention, which need exploration, and which to keep an eye on.

I've found myself changing the way I present myself to my patients. I'm no longer racing to find the answer right away — though sometimes I still do. TerrainDx helps me show off what I'm best at, which is helping the individual in front of me find a way forward. I think most of you will find the same.

A few honest limits. The tool will sometimes waste time or open Pandora's box. It is not a genius diagnostic engine. It has far less subjectivity and far fewer hallucinations than most AI tools, but it can be incorrect or misled. It is evidence-based, and every decision is traceable — every diagnosis points to external references for further perspective.

The full analysis takes a while, so it may be best to have your patient enter the case ahead of time. We're working with partners on quicker ways to capture data while you're doing other things.

The four tools are designed so you can use TerrainDx in just the amount that's helpful:

• TerrainDx Chat — for quick answers, dose checks, evidence verification
• Key Questions — quick and compulsive use as you close your notes, to think briefly about how you might have gotten it wrong
• The Condensed Case — for sharing with colleagues
• The Terrain Map — for brainstorming a case where you feel you might be missing something

Take some time with the demo, or register and enter a case of your own. If you have knowledge-hungry patients, or complex patients where something feels missing, have them go home and explore. I think you'll find it well worth the time.