Bjornson 2004.

Methods	Randomised double‐blind controlled trial
Participants	Study period: September 2001 to April 2002 and September 2002 to February 2003 Setting: 4 paediatric emergency departments (Alberta Children’s Hospital in Calgary, Stollery Children’s Health Centre in Edmonton, Winnipeg Children’s Hospital in Winnipeg, or Children’s Hospital of Eastern Ontario in Ottawa) in Canada Inclusion criteria: children aged 3 months to 9 years with mild croup based on an initial medical evaluation. Mild croup was defined as onset within the past 72 hours of a seal‐like, barking cough and a Westley croup score of ≤ 2. Exclusion criteria: symptoms or signs of another cause of stridor; history of congenital or acquired stridor, asthma, exposure to varicella within the previous 21 days, chronic pulmonary disease, severe systemic disease, or known immune dysfunction; treatment with corticosteroids within the past 2 weeks; treatment of respiratory distress with epinephrine prior to enrolment; those enrolled in another clinical trial in the past 4 weeks; parents unable to speak either English or French; lack of a telephone at home; a prior visit to the emergency department because of croup during this episode of the disease Baseline demographics (N = 720): proportion male: treatment: 61%; control: 61% mean (SD) age in months: treatment: 35 (23); control: 35 (23) Westley croup score: treatment: 38% score of 0, 38% score of 1, 24% score of 2; control: 38% score of 0, 43% score of 1, 19% score of 2
Interventions	Treatment (N = 359): single 0.60 mg/kg (maximum of 20 mg) dose of oral dexamethasone Control (N = 361): single dose of oral placebo (10 mL distilled water) Both treatment and placebo included 50 mL of wild cherry‐flavoured syrup.
Outcomes	Return visits to any healthcare provider within 7 days
Notes	Funding source: Canadian Institutes of Health Research; Alberta Children's Hospital Foundation; Children's Hospital of Eastern Ontario Research Institute; Stollery Children's Hospital Foundation; Cumberland Pharmaceuticals
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "computer‐generated randomization scheme, stratified by centre, used random permuted blocks of 6‐20 children to ensure the comparable assignment of eligible patients."
Allocation concealment (selection bias)	Low risk	Quote: "Codes were secured at each center's pharmacy until enrolment and all decisions regarding data analysis had been finalized." The preparations were "not distinguishable" and "packaged in sequentially numbered, sealed bags."
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Quote: "double‐blind" "Parents were unable to determine which preparation their child had received" "Preparations were not distinguishable by appearance, volume, weight, taste, or smell."
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Quote: "double blind" "Preparations were not distinguishable by appearance, volume, weight, taste, or smell and were packaged in identical syringes in sequentially numbered, sealed bags" "biostatistician who was not otherwise involved in the study performed the data analysis."
Incomplete outcome data (attrition bias) All outcomes	Low risk	Comment: missing data imputed using intention‐to‐treat analysis. 5% (N = 37) protocol deviations equally distributed between groups. 2% (N = 13) had incomplete follow‐up.
Selective reporting (reporting bias)	Unclear risk	Comment: no protocol identified. All prespecified outcomes from methods appear in results.
Other bias	Low risk	Comment: no other sources of bias identified.
Overall risk of bias All outcomes	Unclear risk	Comment: at least 1 domain judged as unclear risk, and no domains judged as high risk.