From differential to targeted questions
This exemplar demonstrates how problem-based clinical reasoning translates a defined diagnosis into a focused differential and a deliberate set of questions. Rather than cataloging symptoms exhaustively, it shows how expert clinicians decide what to ask, why those questions matter, and how overlapping symptoms are handled efficiently.
Why this case exists
This exemplar is not meant to be a comprehensive tutorial on iron deficiency anemia.
It is meant to show how clinicians translate a defined problem into purposeful questioning, including symptoms, without becoming exhaustive or repetitive.
Iron deficiency is a useful teaching example because it forces clinicians to ask many symptom questions, only some of which help identify the cause. Without structure, these questions easily collapse into a long, unfocused list.
The goal here is to show how symptoms can be gathered deliberately, each serving a different purpose, then woven into a coherent history of presenting problems.
Step 0: What “unstructured” often looks like
When learners do not have a cognitive map, symptom gathering becomes a scattershot sequence.
It may sound like this:
“Any fatigue, dizziness, shortness of breath, chest pain, palpitations, headaches, cold intolerance, hair loss, nail changes, cravings, restless legs, abdominal pain, reflux, diarrhea, constipation, black stools, blood in stool, heavy periods, easy bruising, bleeding, weight loss, fevers, night sweats, and are you vegetarian?”
Many of these are reasonable questions.
The problem is that they are asked without a clear ordering principle.
The listener cannot tell what is being tested: severity, biology, or cause.
The clinician cannot easily stop, because the questioning was never prioritized.
Why this matters:
This approach helps clinicians ask fewer, higher-yield questions, avoid repetitive symptom checklists, and enter the encounter with a clear plan for how the history will narrow the differential.
Step 1: Name the problem and the three questions it creates
Problem: iron deficiency anemia
This is not a symptom. It is a diagnostic state, supported by data.
Once the problem is named, the history should be organized around three questions:
- How sick is the patient because of anemia?
- Is iron deficiency clinically meaningful beyond anemia alone?
- Why is the patient iron deficient?
Symptoms help answer all three, but not in the same way.
Two different numbers are driving the reasoning in this case, and they play different roles.
The hemoglobin level functions as a physiologic signal, guiding questions about symptoms, severity, and urgency.
The ferritin level functions as a diagnostic signal, directing attention toward etiology, including blood loss and impaired absorption.
Treating these numbers as interchangeable would obscure both severity assessment and cause.
Step 2: Build a simple differential model and turn it into questions
A mechanism-based model organizes iron deficiency efficiently:
- loss (most commonly blood loss)
- absorption (malabsorption, gastric acid suppression, surgery)
- intake (dietary restriction or low iron intake)
Now translate each branch into questions.
Loss:
menstrual volume and change over time, GI bleeding symptoms, blood donation, other bleeding
Absorption:
bariatric or gastric surgery, celiac-type symptoms, chronic diarrhea, PPI use
Intake:
vegetarian or vegan diet, restricted diet, low iron intake
Notice overlap. Some questions inform multiple branches and are asked once (for example, dietary pattern informs intake and also helps interpret the plausibility of absorption failure).
Disease scripts in practice:
Disease scripts are not lists to recite. In problem-based reasoning, they are used to generate a focused set of questions, then set aside once their job is done.
Step 3: History of presenting problems (HPP)
Scope note
The history of presenting problems is a subsection of the record. Past medical history, family history, social history, medications, allergies, and review of systems are still obtained and documented separately.
The HPP integrates relevant elements from across the full history into a problem-centered narrative. Redundancy is intentional.
History of presenting problems: iron deficiency anemia
The patient is referred for evaluation of iron deficiency anemia identified on recent laboratory testing, with hemoglobin of 9.8 g/dL, mean corpuscular volume of 72 fL, ferritin of 6 ng/mL, and transferrin saturation of 5%.
She reports progressive fatigue over several months, with reduced exercise tolerance and shortness of breath when climbing stairs. She denies chest pain, syncope, or palpitations.
In addition, she describes symptoms consistent with systemic iron depletion, including restless legs at night, increased hair shedding, and brittle nails. She has not noticed pica or other unusual cravings.
In considering potential causes, she reports regular menstrual periods that have become heavier over the past year, with passage of clots and the need to change protection frequently on the first two days. She denies melena, hematochezia, epistaxis, or other bleeding and has no history of blood donation.
Her diet includes meat and iron-containing foods, and she is not vegetarian or vegan. She has not undergone bariatric or gastric surgery and denies chronic diarrhea, bloating, or weight loss suggestive of malabsorption. She takes a proton pump inhibitor daily for gastroesophageal reflux disease.
There is no family history of anemia, thalassemia, or other inherited blood disorders.
Step 4: What to notice, the three symptom roles in action
This history is not organized by systems or chart subsections.
It is organized by the work the information is doing.
Symptoms of anemia
These establish severity and physiologic impact: fatigue, dyspnea on exertion, reduced exercise tolerance. They help determine urgency and treatment intensity. They do not distinguish among causes of iron deficiency, and they are not meant to.
Symptoms of iron deficiency independent of anemia
These reflect the biology of iron depletion itself: restless legs, hair loss, brittle nails, pica. They validate the disease state and explain patient distress, even when anemia is modest. They still do not identify why the patient is iron deficient.
Symptoms and history that discriminate cause
These are embedded in the etiologic narrative: heavy menstrual bleeding, absence of GI bleeding, diet pattern, surgical history, malabsorption symptoms, proton pump inhibitor use, blood donation history. This is where the differential is narrowed.
No symptom was ignored.
No symptom was asked without a reason.
Step 5: Assessment as judgment, not summary
A strong assessment mirrors the same three roles: severity, biology, etiology.
Assessment: iron deficiency anemia with symptomatic iron depletion. Symptoms suggest clinically meaningful iron deficiency beyond hemoglobin level alone. The pattern of heavy menstrual bleeding is the most likely cause, with possible contribution from chronic proton pump inhibitor use. There is no evidence of gastrointestinal bleeding, dietary restriction, malabsorption, or inherited anemia.
This assessment:
- names what matters clinically
- commits to a leading cause
- explains what was considered and excluded
- closes the loop between data, symptoms, and mechanism
This is judgment, not summary.
Quick self-check for learners
- Which symptom questions assessed severity rather than cause?
- Which symptoms supported iron depletion biology even if they did not identify etiology?
- Which historical elements most strongly narrowed the cause?
- If heavy menses were absent, which branch would rise in priority next, and what questions would you ask first?
Final takeaway
Problem-based clinical reasoning is the translation step between knowing a differential and taking a history.
It helps clinicians ask fewer, better questions.
It prevents symptoms from becoming a noisy checklist.
It produces a history that naturally supports a clear assessment and an effective presentation.
The payoff is not less thoroughness.
It is more deliberate thinking.