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]}