Laboratory Tests and Ancillaries
Croup is a clinical diagnosis based on the presence of barking cough and stridor. Diagnostic tests are not routinely done in typical presentations unless an alternative diagnosis is being considered.
Pulse Oximetry
Croup_Diagnostics
Pulse oximetry determines O₂ saturation. Clinical assessment is more important than oximetry results. Patients with symptoms of severe respiratory obstruction may present with nearly normal O₂ saturation on oximetry.
Other Tests
Virologic testing is not necessary in most patients with croup but may be warranted among hospitalized patients to determine the need for isolation. Measurement of serum electrolytes and kidney function may be appropriate in the setting of dehydration or hypovolemia. Complete blood count (CBC) and serum chemistries are rarely indicated.
Imaging
Imaging is not routinely used but may be considered. In chest radiography, the steeple sign is most often manifested in patients with croup. Computed tomography (CT) and laryngoscopy may be considered to rule out other diseases.