Clinical reasoning, problem representation and differential diagnosis — formative SAQs

SAQ 1 — Infant return visit after a viral label (10 marks)

A 7-week-old was discharged yesterday with “likely viral illness.” The caregiver returns overnight saying the baby is more lethargic and “not himself.” First observations are only mildly abnormal. [4] [5]

Questions

1. Write a one-sentence problem representation for this encounter. (3 marks) [1] [2]
2. Build a threat-first differential of up to five items and state residual risks that remain open if a viral working diagnosis is still used. (4 marks) [3] [5]
3. Outline the diagnostic pause and handoff content you would use. (3 marks) [6] [7]

Model answer

Problem representation (3). Previously assessed 7-week-old with overnight return for progressive lethargy and caregiver concern that the infant is not himself after a prior viral label; mild first observations but high residual risk for evolving serious bacterial infection, cardiac or metabolic disease; requires senior review and rewrite of the working diagnosis. Must include age, return context, tempo, caregiver concern and threat posture. [1] [2] [4]

Threat-first differential (4). Immediate threats: serious bacterial infection/sepsis, congenital heart disease with evolving failure, metabolic crisis, evolving respiratory failure, non-accidental injury or other hidden threat as context requires. If a viral working diagnosis remains for action, residual risks must stay explicit: delayed serious infection, cardiac disease, metabolic disease and any safeguarding concern. Prioritise by threat, likelihood, reversibility and harm of delay. [3] [5]

Diagnostic pause and handoff (3). Pause questions: what is the sentence now, what must I not miss, what would change my mind, who else should look. Handover: provisional working diagnosis, residual risks, actions already taken, response, next discriminating step, caregiver concern and review time. Do not hand over “stable viral” alone. [6] [7]

SAQ 2 — Complex child with subtle change (10 marks)

A school-age child with medical complexity and home respiratory support presents because the usual carer says the child is “not their normal.” Staff are tempted to attribute findings to the known diagnoses. [9] [8]

Questions

1. Which elements must enter the problem representation for a technology-dependent child? (3 marks) [9] [2]
2. Name two cognitive traps in this scenario and how you would counter each. (4 marks) [7] [8]
3. How would you explain diagnostic uncertainty to the carer while agreeing a plan? (3 marks) [3] [4]

Model answer

Representation elements (3). Age/development; known baseline diagnoses and devices; what is different from usual; current physiology versus personal baseline; emergency plan or device settings; caregiver expertise and concern; data-quality limits. The sentence must not collapse to “known complex child.” [9] [2]

Traps and counters (4). Anchoring/attribution to the known diagnosis — counter by asking what is new and listing device failure and intercurrent infection as active scripts. Premature closure or diagnostic momentum from prior labels — counter with a diagnostic pause, must-not-miss list and senior review if mismatch persists. Search-satisfying after one familiar finding also deserves a forced second look. [7] [8] [9]

Communication (3). “I think the most likely problem is X. I am still protecting against Y, including device or new infection issues. Here is what we will do now, what we will watch for, and when to escalate.” Acknowledge carer expertise. Avoid false certainty and avoid unsorted rare-disease catalogues. [3] [4]