Stage 5: Formulation & Differential
Concept 3 of 8
E5.3

Working Diagnosis

A diagnosis that drives treatment decisions while remaining open to revision. Better than premature certainty or paralyzing uncertainty.

Encounter card
Setting
After initial assessment, when treatment must begin before all questions are resolved.
Opening move
Commit to the best current diagnosis. Document what is supporting it, what would change it, and what would prompt revisiting. Share the working diagnosis with the patient transparently.
Sample language
  • "Based on what you've told me, my best working understanding is depression — specifically a major depressive episode. I want to be honest that I'm not 100% certain — we should keep an eye on whether it might be something else, like bipolar disorder. But for now, this is what I'm treating."
  • "If you don't respond to this approach, we'll revisit the diagnosis."
Listen for
Patient's reception of the working diagnosis — alignment or disagreement is itself diagnostic information.
Common pitfalls
Refusing to commit because of uncertainty (paralyzes treatment). Committing too rigidly (closes future evidence). Not sharing the working diagnosis with the patient. Not specifying what would prompt revision.

Red flags / escalate: Working diagnosis treatment fails repeatedly — reopen the differential rather than escalating within the same framework.

Documentation
"Working diagnosis: MDD, single episode, moderate severity. Bipolar II remains on differential pending longer course observation; would revise if hypomanic episode emerges or antidepressant-induced activation occurs."

Real-world reality: Working diagnoses are sometimes frozen in charts long after the clinical picture has evolved. Update diagnostic language as evidence changes; the chart should reflect current understanding.

A working diagnosis is a commitment with humility. Commit firmly enough to treat; hold loosely enough to revise.

Warm grey-tinted clinical notebook page, deep ochre accent. The working diagnosis as commitment-with-revision — firm enough to treat, loose enough to revise. Margin clusters on the stance.

A working diagnosis is the clinical move that lets you treat in the face of uncertainty. Paralyzing yourself with diagnostic ambivalence delays needed treatment. Committing rigidly to a diagnosis closes the door on evidence that would revise it. The working diagnosis splits the difference — commit firmly enough to treat, hold loosely enough to revise.

Commit with revision in mind. "Based on what we've discussed, my best working understanding is major depressive disorder. I want to be honest that I'm not 100% certain — there are some things in your history that make me want to keep an open mind, particularly about bipolar disorder. But for now, this is what I'm treating, and here's what we're going to do." Both commitment and humility, stated explicitly.

Define what would prompt revision in advance. "If you have any periods of feeling unusually high or wired, or if the medication makes you feel that way, we'll need to revisit the diagnosis." Setting the revision criteria upfront means you're watching for them, the patient is watching for them, and revision happens when warranted rather than being postponed indefinitely.

Share the working diagnosis transparently with the patient. Patients deserve to know what you think is going on and what you're treating. Honest uncertainty is more trustworthy than false confidence. "I think this is depression. Here's what I'm not sure about. Here's what we'll watch for that would change my mind." That kind of honesty builds alliance and engages the patient in monitoring.

Working diagnoses evolve. The patient diagnosed with major depression three years ago who has had a clearer hypomanic episode is now bipolar II — the diagnosis updates with new evidence. The patient diagnosed with adjustment disorder whose symptoms persist beyond the precipitant may be MDD. The patient's longitudinal course teaches you the diagnosis better than any single cross-sectional encounter.

Document the working diagnosis with the uncertainty. "Working diagnosis: MDD, single episode, moderate severity. Bipolar II remains on differential; would revise if hypomanic episode emerges or antidepressant-induced switch occurs." The chart shows your thinking; the next reader knows what was considered and why this was chosen.

Sharing the working diagnosis transparently — what it is, what it isn't certain about, what would change it. Sample script.
The anchor

A working diagnosis commits firmly enough to treat but remains open to revision. Define in advance what would prompt rethinking.

Defining in advance what evidence would prompt diagnostic revision. Sample examples (treatment failure, new symptoms, medical findings).
Prove it

A patient asks: "Do I have bipolar disorder or depression?" The differential is genuinely uncertain. How do you respond?

This connects to
E5.2
Differential Reasoning
What the working diagnosis emerges from.
E5.6
Reformulation Over Time
How the working diagnosis evolves.

Locked concepts unlock as you reach them on the path.

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