Yale Observation Scale Calculator
Yale Observation Scale Calculator
Six observations weighted 1, 3 or 5, total 6 to 30, derived in febrile children aged 3 to 36 months in 1982. In 4,591 febrile infants aged 60 days or under, a normal score of 10 or less had a sensitivity for serious bacterial infection of 11.6% — which is the most important thing on this page.
Yale Observation Scale
6 items, 6 to 30Strong normal cry (1); cries off and on with parent (3); stays awake (1); pink (1); moist mucous membranes (1); smiles briefly (3)
Scoring, and where the score fails
each item 1 (normal), 3 (moderate impairment) or 5 (severe impairment) · minimum 6 · maximum 30 · 10 or less normal · 11–15 · 16 or more
- the minimum is 6, not 0
- every item scores at least 1, so a well child scores 6. A reported total below 6 is a scoring error, in the same way a Glasgow Coma Scale below 3 is
- the derivation population, and the era
- febrile children aged 3 to 36 months in 1982, with serious illness in 2.7% of those scoring 10 or less, 26% at 11 to 15 and 92.3% above 16. That cohort predates Haemophilus influenzae type b and pneumococcal conjugate vaccination; the prevalence of occult bacteraemia it was built on no longer exists
- and the population it fails in
- 4,591 non-critically ill febrile infants aged 60 days or under, across 26 emergency departments. A score of 10 or less — the normal range — had a sensitivity for serious bacterial infection of 11.6% (95% CI 8.8 to 15.0) and a negative predictive value of 90.4%; for invasive bacterial infection, 24.2% and 98.2%. The authors concluded that neither the score nor unstructured clinician suspicion reliably identified those with invasive bacterial infection
- two renderings of the same six items
- the published scale weights the three levels 1, 3 and 5 for a total of 6 to 30. An independent reproduction of the identical descriptors weights them 1, 2 and 3, for a total of 6 to 18. The descriptors are word for word the same and the totals are not comparable, so record which weighting was used
- what it is not
- it is an observation scale, not a decision rule and not a substitute for the laboratory. A score is not a diagnosis, and the 2017 cohort above is a direct demonstration: a reassuring total in a young febrile infant left 9.6% of them with a serious bacterial infection
Worked example
Strong normal cry (1); cries off and on with parent (3); stays awake (1); pink (1); moist mucous membranes (1); smiles briefly (3)
1 + 3 + 1 + 1 + 1 + 3 = 10 points, at the top of the normal range
In the 1982 derivation population of febrile children aged 3 to 36 months, 2.7% of children scoring 10 or less had a serious illness
Now change only the age. In 4,591 febrile infants aged 60 days or under, 9.6% of those scoring 10 or less had a serious bacterial infection: the score's sensitivity in that population is 11.6%. The arithmetic is identical and the meaning is not
Every item at 1 gives 6, the floor — not 0. Every item at 5 gives 30. A total below 6 cannot exist
On the alternative published weighting of the same six descriptors, 1/2/3 instead of 1/3/5, this child scores 7 of 18. Same observations, different instrument, and the bands above do not apply to it
The six observations
| Observation | 1 — normal | 3 — moderate impairment | 5 — severe impairment |
|---|---|---|---|
| Quality of cry | Strong, normal tone, or content and not crying | Whimpering or sobbing | Weak, moaning, or high-pitched |
| Reaction to parental stimulation | Cries briefly then stops, or content | Cries off and on | Cries continually, or hardly responds |
| State variation | Stays awake, or wakes quickly | Eyes close briefly, or wakes only with prolonged stimulation | Falls asleep, or will not rouse |
| Colour | Pink | Pale extremities or acrocyanosis | Pale, cyanotic, mottled or ashen |
| Hydration | Normal skin and eyes, moist mucous membranes | Normal skin and eyes, slightly dry mouth | Doughy or tented skin, dry mucous membranes, sunken eyes |
| Response to social overtures (over 2 months) | Smiles or alerts | Smiles or alerts briefly | No smile, anxious face, dull expression, or does not alert |
The same score in two populations
| Cohort | Score | What was found |
|---|---|---|
| Derivation, 1982 — febrile children 3 to 36 months | 10 or less | 2.7% had a serious illness |
| Derivation, 1982 | 11 to 15 | 26% had a serious illness |
| Derivation, 1982 | 16 or more | 92.3% had a serious illness |
| 100 febrile children 3 to 36 months, 18% bacteraemic | 20 or more | Sensitivity 100%, specificity 90.2%, PPV 69% for bacteraemia |
| 4,591 febrile infants 60 days or under, 26 emergency departments | 10 or less (normal) | 9.6% still had a serious bacterial infection — sensitivity 11.6% (8.8–15.0), NPV 90.4% |
| The same 4,591 infants | 10 or less (normal) | For invasive bacterial infection: sensitivity 24.2% (16.0–34.1), NPV 98.2% |
An instrument that works where it was built and fails where it is reached for
The Yale Observation Scale asks six questions about how a febrile child looks and behaves: the quality of the cry, whether a parent can console them, whether their state moves normally between sleep and waking, their colour, their hydration, and whether they respond to being talked to and smiled at. Each is graded normal, moderately impaired or severely impaired and weighted 1, 3 or 5. The floor is 6, not 0 — every item scores at least one point — and the ceiling is 30. In the 1982 derivation population of febrile children aged 3 to 36 months, 2.7% of those scoring 10 or less had a serious illness, 26% of those scoring 11 to 15, and 92.3% of those above 16. As a way of writing down what “toxic-looking” means, it was a genuine advance.
Two things have happened since. The first is epidemiological: that cohort predates routine Haemophilus influenzae type b and pneumococcal conjugate vaccination, so the occult bacteraemia the scale was calibrated against has largely gone, and a derivation-era percentage cannot be read off onto a child today. The second is a direct test in the population the scale is most often reached for, and it is the most useful result on this page. In 4,591 non-critically ill, full-term febrile infants aged 60 days or under, across 26 emergency departments in the PECARN network, 4,058 had a normal score of 10 or less — and 9.6% of those infants had a serious bacterial infection. The score’s sensitivity for serious bacterial infection was 11.6% (95% CI 8.8 to 15.0) with a negative predictive value of 90.4%; for invasive bacterial infection, meaning bacteraemia or bacterial meningitis, sensitivity was 24.2% and the negative predictive value 98.2%. The authors’ conclusion was that neither the Yale Observation Scale nor unstructured clinician suspicion reliably identified the infants with invasive bacterial infection.
There is also a quieter problem with the instrument itself. Two published reproductions carry these six descriptors word for word and weight them differently: the scale as published uses 1, 3 and 5 for a total of 6 to 30, and an independent reproduction uses 1, 2 and 3 for a total of 6 to 18. The risk strata belong only to the first. And two of the six items were never designed for a young infant: the social-response item is specified for children over two months, since a social smile is not reliably present before about six weeks, and the consolability item collapses the inconsolable child and the barely responsive child into the same 5.
None of that makes the six observations worthless — they are the observations an experienced clinician makes anyway, and writing them down makes a handover auditable. It makes the total a poor rule-out. A score is not a diagnosis, and a published figure describes the cohort it came from rather than the child in front of you. A single value is a snapshot of one examination: a child whose illness is evolving can score differently an hour later, so a reassuring score does not exclude deterioration, and the trend across serial assessments by the same examiner carries more than any one reading. The derivation population is febrile children aged 3 to 36 months in the early 1980s; the failure population is febrile infants aged 60 days or under today. Published item wordings and severity bands differ between sources and between units, so the reader’s own unit’s chart and protocol take precedence over any banding printed here.
Frequently asked questions
What is a normal Yale Observation Scale score?
10 or less is the normal range, and the floor of the scale is 6 rather than 0 because every item scores at least one point. In the 1982 derivation population of febrile children aged 3 to 36 months, 2.7% of children scoring 10 or less had a serious illness.
Can the Yale Observation Scale rule out serious infection in a young infant?
No, and that is the clearest finding about it. In 4,591 febrile infants aged 60 days or under, a normal score of 10 or less had a sensitivity for serious bacterial infection of 11.6% and a negative predictive value of 90.4%; 9.6% of infants with a normal score had a serious bacterial infection. The study’s authors concluded that neither the score nor unstructured clinician suspicion reliably identified those with invasive bacterial infection.
What age range is the Yale Observation Scale for?
It was derived in febrile children aged 3 to 36 months, and its social-response item is specified for children over 2 months. It performs poorly in infants aged 60 days or under, which is below the population it was built in.
Why do some versions of the scale score 1, 2 and 3?
Because two published reproductions of the identical six descriptors use different weights: the scale as published uses 1, 3 and 5 for a total of 6 to 30, while another reproduction uses 1, 2 and 3 for a total of 6 to 18. The totals are not comparable and the published risk strata apply only to the 1/3/5 version, so record which was used.
Is the Yale Observation Scale the same as assessing level of consciousness?
No. Its state-variation item overlaps with arousal, but the paediatric Glasgow Coma Scale grades responsiveness to a defined stimulus while this item grades whether a child’s state moves normally between sleep and waking. The two answer different questions and neither replaces the other.
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References
- McCarthy PL, Sharpe MR, Spiesel SZ, et al. Observation scales to identify serious illness in febrile children. Pediatrics. 1982;70(5):802–809. The item descriptors and the three risk strata are quoted here from FPnotebook’s Yale Scale for Febrile Child 3 to 36 Months and from the independent reproduction in Asian J Pharm Clin Res (Innovare), both read in full; the 1982 paper was not opened.
- Nigrovic LE, Mahajan PV, Blumberg SM, et al. The Yale Observation Scale score and the risk of serious bacterial infections in febrile infants. Pediatrics. 2017;140(1):e20170695 — 4,591 febrile infants 60 days and under across 26 emergency departments in the PECARN network.
- Richards EP (ed). P. L. McCarthy’s technique for evaluating pediatric patients, Exhibit 7-1, LSU Medical and Public Health Law Site (accessed 10 October 2026) — an independent reproduction of the same six descriptors, weighted 1/2/3 rather than 1/3/5, which is the disagreement printed on this page.
- Efficacy of the Yale Observation Scale to detect serious bacterial infection in febrile children aged one to 36 months. Asian J Pharm Clin Res — 100 febrile children aged 3 to 36 months at Kasturba Medical College, Mangalore, 18% bacteraemic; at a score of 20 or more, sensitivity 100%, specificity 90.2%, positive predictive value 69% (full text read).
Not medical advice. For healthcare professionals and education. Reference intervals vary by laboratory and assay — always use your own laboratory's. Never base a dose or a treatment decision on this page alone. Full disclaimer at calcengines.com/disclaimer/