Diagnosis of Croup in Children
Croup is diagnosed clinically based on the characteristic presentation of sudden-onset barking cough, inspiratory stridor, hoarse voice, and respiratory distress, without the need for laboratory testing or imaging in typical cases. 1, 2, 3
Clinical Diagnostic Criteria
The diagnosis relies on recognizing the classic triad:
- Barking or "seal-like" cough that distinguishes croup from other respiratory illnesses 2, 4, 3
- Inspiratory stridor, particularly at rest in moderate to severe cases 1, 4
- Hoarse voice or cry resulting from laryngeal inflammation 5, 3
Most cases present with preceding upper respiratory symptoms including low-grade fever and coryza for 12-48 hours before the characteristic cough develops. 2, 4 The symptoms typically affect children between 6 months and 6 years of age, with peak incidence in the second year of life. 2, 4, 3
Severity Assessment
Immediate assessment should focus on identifying severity indicators and life-threatening signs rather than obtaining diagnostic tests. 1 Key clinical features to evaluate include:
- Ability to speak or cry normally - loss indicates more severe obstruction 1
- Presence of stridor at rest versus only with agitation 1, 5
- Use of accessory muscles (suprasternal, intercostal retractions) 1
- Respiratory rate and work of breathing 1
- Oxygen saturation - values <92-94% indicate significant disease 1, 6
Life-threatening signs requiring immediate intervention include silent chest (absence of breath sounds despite respiratory effort), cyanosis, fatigue/exhaustion, or poor respiratory effort. 1
Diagnostic Testing: What to Avoid
Radiographic studies are generally unnecessary and should be avoided unless there is concern for an alternative diagnosis. 1, 6 The diagnosis of croup is clinical, and imaging does not change management in typical presentations. 3
Laboratory studies including viral cultures and rapid antigen testing have minimal impact on management and are not routinely recommended. 3 Croup is most commonly caused by parainfluenza viruses (types 1-3), but identifying the specific pathogen does not alter treatment. 7, 2
Laryngoscopy should be reserved only for patients in whom alternative diagnoses are suspected, as it may worsen airway obstruction and cause unnecessary distress. 3
Critical Differential Diagnoses to Exclude
While croup is diagnosed clinically, you must actively consider and exclude more serious conditions:
- Bacterial tracheitis - presents with high fever, toxic appearance, and rapid progression 1, 2
- Epiglottitis - characterized by drooling, inability to swallow, tripod positioning, and toxic appearance 2, 4
- Foreign body aspiration - sudden onset without prodromal illness, unilateral findings, history of choking episode 1, 2
- Retropharyngeal or peritonsillar abscess - severe dysphagia, neck stiffness, asymmetric findings 2, 4
The key distinguishing feature is that croup typically has a gradual onset with preceding viral symptoms, while these alternative diagnoses present more acutely or with distinct clinical features. 2, 4
Special Considerations for Recurrent Croup
Recurrent episodes of croup warrant consideration of asthma as a differential diagnosis, especially if cough worsens at night, episodes are triggered by exercise or irritants, or there is a family history of asthma or atopy. 1 The presence of atopic dermatitis or gastroesophageal reflux symptoms should also be evaluated in children with multiple croup episodes. 1
Common Diagnostic Pitfalls
Do not perform blind finger sweeps in cases of suspected foreign body aspiration, as this may push objects further into the pharynx and worsen obstruction. 1
Do not rely on lateral neck radiographs for diagnosis - clinical assessment is more important and radiographs are often unnecessary in typical croup presentations. 1
Avoid causing undue distress during examination, as agitation increases oxygen demand and can worsen airway obstruction. 5 Assessment should be performed with the child in a position of comfort, typically in the parent's arms.