Neither of these decision rules have been validated
300 Infants in a single center with 76% admission rate with 37 (12%) required significant intervention
Prematurity
Abnormal physical examination
Color change to cyanosis,
Absence of upper respiratory infection symptoms and the absence of choking
Negative predictive value: 96%
Specificity of 70.5%
7 out of the 184 (3.8%) were incorrectly discharged
832 patients from 4 different study sites, with a 79.2% admission rate
Obvious need for admission:
Supplemental Oxygen requirement
Resuscitation
Hemodynamic Instability
Positive RSV or Pertussis test
Significant past medical history
Congenital heart disease
Down syndrome
Previous intubation
Chromosomal abnormality
Chronic lung disease (e.g. bronchopulmonary dysplasia)
> 1 BRUE in 24 hours
Negative predictive value of 96.5%
Sensitivity of 89% , a Specificity of 61.9% , and a calculated
14 (2%) patients were incorrectly discharged
Supplemental Oxygen requirement
Resuscitation
Hemodynamic Instability
Positive RSV or Pertussis test
Congenital heart disease
Down syndrome
Previous intubation
Brief resolved unexplained event
The differential diagnosis is extensive, and although a broad workup is often started in the ED including evaluation for sepsis, occult infection, and metabolic disorders, a cause is infrequently found[2]
Deterioration after intubation
Idiopathic 
Headache during pregnancy
GERD
Acute chest pain
Seizure