Yale Observation Scale For Infant Fever

Evaluates febrile status in urgent and non-urgent pediatric clinical care.

In the text below the calculator there is in depth information on the score interpretation and on the original study.

The Yale observation scale for infant fever is used in the assessment of pediatric patients (3 to 36 months) presenting to ER or pediatric departments with fever greater than 101.3 F (38.5 C).

The scale accompanies other investigation and stratifies the likelihood of serious illness, in most cases, this refers to occult bacteremia.

The six criteria used in the evaluation of the infant physical aspect and behaviour are:

■ Quality of cry;

■ Reaction to parents;

■ State variation;

■ Colour;

■ Hydration;

■ Social response.

The six criteria in the Yale observation scale are awarded between 1 and 5 points each.

The final score ranges between 0 and 30. The following table summarises the correlation between Yale scores serious illness incidence rate:

Yale observation scale result (points) Serious illness incidence rate
< 10 No serious threat
10 2.7%
11 - 15 26%
≥ 16 Up to 92.3%


Quality of cry


Reaction to parents


State variation






Social response

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Yale Observation Scale

The Yale model is used in pediatric departments and in the ER to evaluate patients exhibiting fever on presentation.

The model is used along other determinations and clinical judgement to predict the likeliness of a serious infection, in most cases, an occult bacteremia.

Occult bacteremia suggestive findings include temperature with positive blood cultures and WBC count significant with infection.

The scale is addressed to children aged 3 to 36 months who require physical examination and present with fever greater than 101.3 F (38.5 C).

Re-evaluation is required if the febrile state persists more than 48 hours.

The Yale scale consists of 6 criteria that evaluate changes observed in the appearance and behaviour of the infant.

In the table below you can find the items in the Yale observation scale, along with the answer choices and the number of points awarded to each option.

Yale observation scale items Answer choices (points)
Quality of cry Strong or no cry (1)
Whimper or sob (3)
Weak cry, moan, or high pitched cry (5)
Reaction to parents Brief cry or content (1)
Cries off and on (3)
Persistent cry (5)
State variation Awakens quickly (1)
Difficult to awaken (3)
No arousal or falls asleep (5)
Colour Pink (1)
Acrocyanosis (3)
Pale, cyanotic, or mottled (5)
Hydration Eyes, skin, and mucus membranes moist (1)
Mouth slightly dry (3)
Mucus membranes dry, eyes sunken (5)
Social response Alert or smiles (1)
Alert or brief smile (3)
No smile, anxious, or dull (5

There are other criteria scales for feverish infant assessment, such as the Rochester criteria for new born to infants of 60 days, the Philadelphia criteria for febrile infants 29 – 60 days and the Boston criteria 28 – 89 days.


Score interpretation

Each of the six criteria is accompanied by 3 answer choices that refer to the stages of the respective item.

The first stage and the least serious is awarded 1 point, the second stage is awarded 3 points while the third and most severe stage is given 5 points.

The Yale observation scale results vary between 0 and 30 and present a cut off at 10 points, as described below:

Scores lower than 10 indicate that the present condition does not carry a serious threat to the health of the infant, however, monitoring should continue.

■ Scores of 10 are considered to indicate a serious illness incidence of 2.7%.

■ Scores between 11 and 15 carry a serious illness incidence rate of 26%.

■ Scores of 16 and above indicate that the likelihood of serious illness risk is of up to 92.3%.


About the original study

The Yale observation scale was created by Dr Bang in 2009 following a study that involved 219 consecutive febrile patients aged between 3 and 36 months, with an average of 15.24 months.

Rectal temperature was registered before the subjects were given antipyretics. Of these, bacteremia was diagnosed in 28.16%.

Different cut off values for a positive YOS test were established at 8, 10 and 12 and then tested plotting ROC curve. 10 was found to be the best cut off for prediction of bacteremia.

The scale was found to have high sensitivity and reproducibility. The chance corrected inter-observer agreement (kappa) was 0.7919.


Sepsis in infants and children

Sepsis is the immune system response to an infection that determines the body to activate fighting mechanisms to combat infection.

Neonatal sepsis is defined as the blood infection occurring in infants younger than 3 months with an early onset in the first week of life.

Pediatric sepsis occurs due to an infection coming on a decreased immune protection setting and can occur at any point.

Young children’s immunity system is not yet equipped with an own skilled set of antibodies to fight off infection properly.

The following table summarises the most common sepsis signs:

Fever Temperature > 101.3 F (38.5 C)
Hypothermia Temperature < 96.8 F (36.0 C)
Tachycardia Heart rate over age based normal value
Tachypnea Respiratory rate over age based normal value
Hypotension Systolic blood pressure with high vascular resistance
Vasoconstriction Peripheral, cold extremities, cold shock
Appearance Irritable, lethargic, sleep and feeding disturbances
Skin Petechiae, purpura, paleness

Original source

Bang A, Chaturvedi P. Yale Observation Scale for prediction of bacteremia in febrile children. Indian J Pediatr. 2009; 76(6):599-604.

Other references

1. McCarthy PL, Sharpe MR, Spiesel SZ, Dolan TF, Forsyth BW, DeWitt TG, Fink HD, Baron MA, Cicchetti DV. Observation scales to identify serious illness in febrile children. Pediatrics. 1982; 70(5):802-9.

2. McCarthy PL, Lembo RM, Fink HD, Baron MA, Cicchetti DV. Observation, history, and physical examination in diagnosis of serious illnesses in febrile children less than or equal to 24 months. J Pediatr. 1987; 110(1):26-30.

Specialty: Pediatrics

Objective: Evaluation

Type: Scale

No. Of Items: 6

Year Of Study: 2009

Article By: Denise Nedea

Published On: March 22, 2017

Last Checked: March 22, 2017

Next Review: March 22, 2023