Clinical reasoning exercises for pediatrics

A two-year-old child arrives with a fever that started a day ago. She is in her mother's lap, quiet, and the mother says: "she has never been like this". The exam shows nothing that draws attention. A study of nearly four thousand children seen in primary care in Belgium showed that parents' concern that the illness was different from previous ones was the context factor most linked to the doctor's intuition that something was wrong (Van den Bruel et al., 2012).

NEXO is a daily medical diagnosis game: one clinical case a day, six progressive clues, and ICD-10 proximity feedback across five levels.

Clinical reasoning in children uses the same tools as in adults, but the data arrive differently: through observation, through the account of whoever provides care and through signs that change with age. This text gathers exercises to train these differences, with commented vignettes and a checklist at the end.

Key points

• In pediatrics, much of the information comes from observing the child and from the parents' account, and both enter the reasoning as data.
• The pediatric assessment triangle organizes the first impression into appearance, work of breathing and skin circulation.
• Red flags increase the probability of serious illness, but no single sign safely rules out serious illness.
• The intuition that something is wrong has value and calls for an action, such as reassessing, asking for an opinion or investigating.
• Illness scripts organized by complaint help compare hypotheses quickly and are easy to train.

Summary

• What changes in the clinical reasoning of children
• Exercise 1: the first impression in a few seconds
• Exercise 2: weighing red flags
• Exercise 3: listening to parents and to your own intuition
• Exercise 4: illness scripts by complaint
• Commented vignettes
• How to train with short cases
• Frequently asked questions
• Checklist for clinical reasoning in pediatrics

What changes in the clinical reasoning of children

The general path is the same as always: collect data, form hypotheses, weigh the probability of each one and decide. If you want to review this base, the text on how to develop clinical reasoning in the clinical cycle explains the steps. Here the focus is on what pediatrics adds.

The history comes from another person

In a small child, the person telling the history is an adult. This brings two tasks: separating what the parents saw from what they interpreted and valuing the comparison that only they can make, that of how the child usually is. The text on signs, symptoms and history shows how to read the account as clinical data; in pediatrics, the parents' account is one of those data.

Behavior is a clinical sign

Playing, smiling, following with the gaze, crying strongly or lying limp in the lap say a lot about the child's state. In the Belgian study, the findings most linked to the doctor's intuition were the child's general response, such as drowsiness and not laughing, altered breathing, weight loss and seizures (Van den Bruel et al., 2012).

Age changes normal values and hypotheses

Respiratory rate, heart rate and the most likely illnesses change with age. The same number can be normal in an infant and altered in an older child. That is why, in the exercises below, the first question is always: what is the age, and what is expected for it?

Where the error usually appears

In a survey answered by 726 pediatricians from three tertiary institutions and 109 affiliated clinics, the diagnosis of a viral disease that was actually bacterial was the most cited diagnostic error, followed by adverse drug effect, psychiatric disorders and appendicitis (Singh et al., 2010). The most reported process failure was not collecting information through the history, the physical exam or the review of the chart (Singh et al., 2010).

More than half (54%) of the pediatricians reported making a diagnostic error at least once or twice a month, and among residents this proportion was 77% (Singh et al., 2010). The numbers come from the doctors' own perception, not from an audit, but they show where it is worth training: complete data collection and attention to the bacterial infection that looks like a viral one.

Exercise 1: the first impression in a few seconds

Before touching the child, you can learn a lot just by looking. The pediatric assessment triangle is a rapid observation tool, designed for the emergency setting and applicable whatever the complaint or the underlying diagnosis (Dieckmann et al., 2010).

The three sides of the triangle

A recent narrative review describes the three components assessed: appearance, work of breathing and skin circulation (Rath et al., 2026). According to the authors, validation studies reported good ability to identify more severe conditions, such as respiratory distress, shock and altered mental status, with limitations such as variation between observers and lower applicability in newborns (Rath et al., 2026).

Side of the triangle	What to observe	Exercise question
Appearance	Tone, interaction, gaze, consolability, speech or cry	Is this child interacting as expected for their age?
Work of breathing	Noises, retractions, position, nasal flaring	Is the child working hard to breathe?
Skin circulation	Color, pallor, mottled skin, cyanosis	Does the skin suggest that blood is arriving well?

Table source: components of the triangle according to Rath et al., 2026; the observation items and the questions are a teaching organization by the Editorial.

How to do the exercise

1. Before reading the story of a vignette, read only the description of the child.
2. Classify each side of the triangle as normal or abnormal.
3. Say which side worries you most and why.
4. Only then read the complaint and the history, and see whether your initial impression changed.

The goal is to separate two questions that often get mixed up: "how sick is this child?" and "what do they have?". The first comes before and defines the urgency; the second comes from diagnostic reasoning.

What the exercise trains

It trains structured observation and keeps the first impression from staying only at "looks well" or "looks unwell". With practice, you start to say which finding supports your impression, which makes the conversation with the preceptor more objective.

Exercise 2: weighing red flags

Red flags are findings that greatly increase the chance of serious illness. To use them well, it helps to think in terms of likelihood ratio, the number that says how much a finding shifts the probability. The text on pretest probability explains the concept; here it is applied to the child with fever.

What the systematic review showed

A systematic review gathered 30 studies on clinical signs of serious infection in children seen outside the hospital in developed countries (Van den Bruel et al., 2010). The authors considered a red flag any finding with a positive likelihood ratio above 5, and an exclusion sign any finding with a negative likelihood ratio below 0.2 (Van den Bruel et al., 2010).

Cyanosis, rapid breathing, poor peripheral perfusion and petechial spots appeared as red flags in several studies (Van den Bruel et al., 2010). The most important conclusion for reasoning was another one: no single sign had value to exclude serious infection, although some combinations helped (Van den Bruel et al., 2010).

The traffic light of the British guideline

The NICE guideline for fever in children under 5 addresses the assessment and initial management of fever without an apparent cause and aims to help recognize serious illness in primary and secondary care (NICE, NG143). It organizes the signs by color, in a traffic light system, and the red ones are the most serious (Kerkhof et al., 2014).

A study validated 16 of these red signs in seven primary care and emergency scenarios, with 6,260 children (Kerkhof et al., 2014). Almost all increased the probability of serious infection, but only four raised the chance substantially in more than one data set: not waking or not staying awake, reduced skin turgor, spots that do not fade under pressure and focal neurological signs (Kerkhof et al., 2014).

How to do the exercise

1. Take a vignette of a child with fever and list all the findings.
2. Mark which are red flags and which are only compatible with mild illness.
3. For each red flag, say whether it alone changes your management or whether it needs another finding alongside it.
4. Say what you would need to see to consider serious illness unlikely, and notice that the answer almost always involves a combination of findings and a reassessment.

Question	Why it matters
Does this finding greatly increase the chance of serious illness?	Warning signs serve to confirm suspicion, not to reassure
Does the absence of this finding reassure?	In the review, a single sign was not enough to rule out serious infection
What combination of data would make me more confident?	Some combinations helped rule out serious infection
What do I do if the impression changes?	Reassessment is part of the decision

Table source: Editorial questions based on the conclusions of Van den Bruel et al., 2010 and Kerkhof et al., 2014.

Tests come after the clinical assessment

Tests can add information to the clinical assessment. In a study of 5,517 children seen in outpatient clinics and emergency departments in Belgium, the authors developed an algorithm that combined clinical signs with C-reactive protein measured at the bedside and pointed to the need for prospective validation (Verbakel et al., 2018). For the exercise, the point is the order: first the clinical assessment, then the question about which test would change the decision. The text on clinical decision-making explores this choice further.

Exercise 3: listening to parents and to your own intuition

The feeling that "something is wrong" is often treated as unscientific. In pediatrics, there are studies that measured its value.

What the numbers say

In the systematic review, parental concern and clinician intuition appeared as strong warning signs in a primary care study, with positive likelihood ratios of 14.4 and 23.5 (Van den Bruel et al., 2010). The same review reported that pneumonia became very unlikely when the child had no shortness of breath and the parents were not concerned, with a negative likelihood ratio of 0.07 (Van den Bruel et al., 2010).

In the Belgian observational study, the intuition that something was wrong, even with a clinical assessment of non-serious illness, greatly increased the risk of serious illness, with a likelihood ratio of 25.5 (Van den Bruel et al., 2012). Acting on this intuition could have prevented two of the six serious cases from going unnoticed, at the cost of 44 false alarms (Van den Bruel et al., 2012).

Intuition calls for action

The authors conclude that intuition should lead to action, such as seeking a second opinion or investigating further (Van den Bruel et al., 2012). They also suggest that, by reflecting on the origin of this feeling, the clinician can improve their own skills (Van den Bruel et al., 2012).

That last sentence is the exercise. Intuition has an origin, and it can almost always be named: the child did not smile even once, the breathing was different, the mother said she had never seen her like that.

How to do the exercise

1. When you finish a vignette, say whether you felt reassured or worried, before thinking about the diagnosis.
2. Write down which piece of data generated that feeling.
3. If the concern came from a parent's account, rewrite the account as an objective question: what exactly is different from other times?
4. Decide which action the concern calls for: reassess soon, call someone more experienced or investigate.

Beware the opposite side

According to the numbers from the Belgian study, acting on intuition would bring 44 false alarms for two serious cases identified (Van den Bruel et al., 2012). That is why intuition works as a trigger to look again, not as a diagnosis. It can also come from a recent memorable case, a bias that the text on differential diagnosis with clues helps to recognize.

Exercise 4: illness scripts by complaint

An illness script is how we store what we know about each disease: who usually gets it, how it starts, what appears on examination and how it evolves. In pediatrics, organizing these scripts by main complaint helps to compare hypotheses quickly.

What a curriculum with scripts found

A curriculum called CRISP used concepts of clinical reasoning and comparison of illness scripts to teach four common pediatric complaints to family medicine residents in a pediatric ward (Madduri et al., 2024). The complaints were respiratory distress, abdominal pain, acute febrile limping and febrile infant in good general condition (Madduri et al., 2024).

Residents and hospitalists preferred the format over traditional lectures, and scores before and after increased in all four sessions; in respiratory distress, for example, they went from 72% to 92% (Madduri et al., 2024). The before-and-after design, without a comparison group, limits what can be concluded about the cause of the improvement.

Another pilot curriculum, with five one-hour sessions for pediatric residents, increased self-rated competence and comfort with clinical reasoning skills (Bowen et al., 2024). Among those who attended at least one session, 97% found the sessions useful (Bowen et al., 2024). Here too the results are self-rated, not performance measured with patients.

How to build your script

Choose a complaint and build a table with three or four hypotheses side by side. Use the columns below and fill them in with what you learned in classes and reference books.

Column	What to write
Who usually has it	Age range, risk factors, context
How it starts	Time of progression, initial symptom
What stands out most	The finding that brings you closest to this hypothesis
What separates it from the others	The data point that distinguishes this hypothesis from the neighboring one in the table
What must not be missed	If this is the serious hypothesis, which sign calls for immediate action

Source of the table: teaching structure from the Editorial inspired by the comparison of scripts described by Madduri et al., 2024; the content of each script must come from your school's clinical references.

How to do the exercise

1. Choose a common complaint, such as fever, cough, abdominal pain or limping.
2. Build the table with the most likely hypotheses for the age and at least one serious one.
3. Read a vignette and mark, line by line, which script each data point favors.
4. At the end, say which data point was decisive and which was missing.

This exercise trains comparison, which is the core of differential diagnosis. The idea is the same as in the text on case-based learning, applied to one complaint at a time.

Commented vignettes

The vignettes below were written by the Editorial to train the four exercises. They are short on purpose and do not replace guidelines or the assessment of the treating clinician. Read the vignette, try to answer the questions, and only then read the comment.

Vignette 1: the infant who is too quiet

An eight-month-old infant has had a fever since yesterday. She is on her parent's lap, pale, looks little at the examiner and does not smile. Her breathing seems calm. The father reports that she is usually fussy and today "wants nothing".

Questions: how is the triangle? Which data point from the history weighs most? What action does your impression call for?

Comment: appearance is the altered side of the triangle, with little interaction and no smile, and pale skin calls for attention to circulation. The father's report brings the comparison with usual behavior, the kind of concern that studies have associated with higher risk of serious illness (Van den Bruel et al., 2012). Even without a clear focus of infection, the impression calls for careful evaluation and close reassessment, not a rushed discharge.

Vignette 2: the boy who coughs and plays

A four-year-old boy has had a cough and runny nose for three days, with low fever. He walks into the office, plays with the toys and talks. There is no effort to breathe, and his skin color is normal. The mother is calm and just wants to know if he can go to school.

Questions: how is the triangle? Which hypotheses go into the cough script? What would change your management?

Comment: all three sides of the triangle are normal, and the combination of no shortness of breath with parents who are not concerned was associated with pneumonia being very unlikely in the systematic review (Van den Bruel et al., 2010). The cough script includes viral airway infections and other hypotheses that depend on age and history. What changes management is the course: explaining to parents which signs call for a return visit is part of the decision.

Vignette 3: fever with spots

A three-year-old girl has had a fever for a few hours and is drowsy. On the skin of her legs, small purple spots appear that do not fade when pressed with a glass cup. The mother says she was fine in the morning.

Questions: what warning signs do you find? Does any one of them, alone, already change management?

Comment: difficulty staying awake and spots that do not fade under pressure are among the red flags that most raised the probability of serious infection in the validation study (Kerkhof et al., 2014). Faced with signs like these, the priority is immediate assessment according to the service protocols. The exercise here is to quickly recognize that the question "what does she have?" comes after the question "how sick is she?".

Vignette 4: the boy who started limping

A six-year-old boy started limping yesterday. He has a low fever and does not want to put weight on one of his legs. He had a cold the previous week. His mother does not remember any fall.

Questions: which hypotheses go into the febrile limping script? Which piece of data would separate the most benign hypothesis from the most serious one?

Comment: acute febrile limping was one of the complaints used in the illness script curriculum (Madduri et al., 2024). The exercise is to build the table with the benign inflammatory and the infectious causes of joint and bone, and to write which finding and which test would help separate them from one another. The exact content of each script must be checked against the clinical references and with the preceptor.

How to train with short cases

The exercises above get stronger with volume: many decisions, each followed by feedback. Short cases with data that arrive gradually reproduce well the way information appears in a pediatric consultation.

A weekly study script

1. Choose one pediatric complaint per week and build its illness script.
2. Solve vignettes of the complaint using the triangle before reading the history.
3. In each vignette, mark the red flags and say which action your impression calls for.
4. Write down the mistakes and the missing piece of data, and review at the end of the week.

Training on NEXO

On NEXO, each case arrives in up to six clues, one at a time, and you decide when to make a guess by the diagnosis name or by the ICD-10 code. With each wrong guess, the game shows the proximity in five levels, from different chapter to exact ICD, and opens the next clue. This trains the same movement as the exercises: forming a hypothesis with incomplete information and adjusting with the next piece of data.

The Diary brings one case per day, and the Archive gathers the previous daily cases for more practice. Multimedia brings cases with image, audio and other exams, which helps train observation. Adrenaline adds time, and Continents changes the background epidemiology. How each mode is unlocked is explained on the NEXO economy page.

Saving and discussing

When a case shows a red flag that you did not value, the Anki button creates the card straight from NEXO and opens it in the Anki app. With your class, the Group tab of the ranking, which gathers invited colleagues, lets you compare at which clue each person got it right and discuss why. If you coordinate a pediatrics league, a medical school or a residency and want to use cases like these in teaching, check out NEXO Closer. Pediatricians who want to review cases in the specialty can take part through NEXO Curator, and researchers interested in clinical reasoning can propose studies through NEXO Researcher. Those who produce medical content can check out NEXO Creators.

Frequently asked questions

What changes in the clinical reasoning of a child?

The steps are the same, but the history usually comes from the parents, the child's behavior works as a clinical sign and normal values change with age. The process failure most reported by pediatricians was not collecting information through the history, the exam or the chart (Singh et al., 2010).

What is the pediatric assessment triangle?

It is a rapid observation tool that assesses appearance, work of breathing and circulation of the skin to identify children in a serious condition (Rath et al., 2026). It can be used whatever the complaint (Dieckmann et al., 2010).

Should parents' concern enter the reasoning?

It should. In the systematic review, parents' concern appeared as a strong red flag in a primary care study (Van den Bruel et al., 2010). It is worth translating the concern into objective questions about what changed.

Does a missing red flag reassure?

Only in combination with other data. The systematic review concluded that no single sign had value to rule out serious infection, although some combinations helped (Van den Bruel et al., 2010).

Is clinical intuition worth anything?

Studies indicate yes, as a trigger to act. The intuition that something was wrong increased the risk of serious illness even when the clinical assessment seemed calm, and the authors recommend that it lead to an action, such as asking for an opinion or investigating (Van den Bruel et al., 2012).

How do you build illness scripts for pediatrics?

Organize by chief complaint and compare hypotheses side by side: who usually has it, how it starts, what draws attention and what separates one from the other. A curriculum with this format increased residents' scores in four common complaints (Madduri et al., 2024).

How does NEXO help train clinical reasoning?

In NEXO, you receive the case in up to six clues and see the proximity of your guess in ICD-10 with each attempt, which trains you to form and adjust hypotheses with incomplete information. To learn about the game, read what NEXO is.

Clinical reasoning checklist in pediatrics

1. Start with age and with what is expected for it.
2. Look before you touch: appearance, breathing effort and skin circulation.
3. Separate severity from diagnosis: first how sick, then what.
4. Treat the parents' report as data and ask what changed.
5. Look for warning signs and remember that the absence of a sign does not rule out serious illness.
6. Name the origin of your intuition and decide what action it calls for.
7. Compare illness scripts side by side for the chief complaint.
8. Keep the serious hypothesis on the list until you rule it out.
9. Choose tests by the question they answer.
10. Set up the reassessment and explain to the parents when to return.

Want to train hypotheses with incomplete information today? Play the case of the day on NEXO.

References

1. Van den Bruel A, Haj-Hassan T, Thompson M, Buntinx F, Mant D. Diagnostic value of clinical features at presentation to identify serious infection in children in developed countries: a systematic review. Lancet. 2010. https://pubmed.ncbi.nlm.nih.gov/20132979/
2. Van den Bruel A, Thompson M, Buntinx F, Mant D. Clinicians' gut feeling about serious infections in children: observational study. BMJ. 2012. https://pubmed.ncbi.nlm.nih.gov/23015034/
3. Kerkhof E, Lakhanpaul M, Ray S, et al. The predictive value of the NICE "red traffic lights" in acutely ill children. PLoS One. 2014. https://pubmed.ncbi.nlm.nih.gov/24633015/
4. National Institute for Health and Care Excellence. Fever in under 5s: assessment and initial management (NG143). https://www.nice.org.uk/guidance/ng143
5. Verbakel JY, Lemiengre MB, De Burghgraeve T, et al. Point-of-care C reactive protein to identify serious infection in acutely ill children presenting to hospital: prospective cohort study. Arch Dis Child. 2018. https://pubmed.ncbi.nlm.nih.gov/29269559/
6. Singh H, Thomas EJ, Wilson L, et al. Errors of diagnosis in pediatric practice: a multisite survey. Pediatrics. 2010. https://pubmed.ncbi.nlm.nih.gov/20566604/
7. Dieckmann RA, Brownstein D, Gausche-Hill M. The pediatric assessment triangle: a novel approach for the rapid evaluation of children. Pediatr Emerg Care. 2010. https://pubmed.ncbi.nlm.nih.gov/20386420/
8. Rath S, Alsabri M, Alhaddad J, et al. Clinical accuracy and applications of the Pediatric Assessment Triangle in emergency care: a narrative review. Int J Emerg Med. 2026. https://pubmed.ncbi.nlm.nih.gov/41975271/
9. Madduri GB, Torwekar EL, Demirel S, et al. CRISP: An Inpatient Pediatric Curriculum for Family Medicine Residents Using Clinical Reasoning and Illness Scripts. MedEdPORTAL. 2024. https://pubmed.ncbi.nlm.nih.gov/38524942/
10. Bowen J, Polak C, Thomson J, Herrmann L. A Pilot Longitudinal Clinical Reasoning Curriculum for Pediatric Residents. MedEdPORTAL. 2024. https://pubmed.ncbi.nlm.nih.gov/39323975/