Geelhoed 1995a.

Methods	Randomised double‐blind controlled trial (trial A; see Geelhoed 1995b for trial B)
Participants	Study period: July 1994 to August 1994 Setting: Princess Margaret Hospital for Children, Perth, Australia Inclusion criteria: children older than 3 months admitted to the hospital with a diagnosis of croup (acute onset of inspiratory stridor, chest wall retractions, barking cough, and hoarse voice) and a minimum modified Westley croup score of 3 Exclusion criteria: other acute or chronic medical problems; modified Westley croup score < 3 (mild croup); families without a telephone or with limited English language abilities; any kind of steroid therapy in the past week; pre‐existing upper airway condition; history of prolonged stridor; those presenting with a clinical picture suggesting a diagnosis other than croup; admitted directly to the intensive care unit with severe croup Baseline demographics (N = 60): proportion male: treatment: 62%; comparator: 81% mean (SD) age in months: treatment: 35 (19); comparator: 42 (27) mean modified Westley croup score: treatment: 3.8; comparator: 3.7
Interventions	Treatment (N = 29): single 0.30 mg/kg (maximum 6 mg) dose of oral dexamethasone Comparator (N = 31): single 0.60 mg/kg (maximum 12 mg) of oral dexamethasone
Outcomes	Change in modified Westley croup score from baseline to 2 and 4 hours; re‐presentations with croup; length of hospital stay; use of epinephrine and use of additional glucocorticoids
Notes	Study reports on 2 comparisons. Funding source: not reported
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Comment: insufficient information provided to judge.
Allocation concealment (selection bias)	Unclear risk	Comment: insufficient information provided to judge.
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Quote: "treatments were administered in a double blind fashion" "If the child was withdrawn from the study, their study code was broken." Comment: described as double‐blind. Unclear who was blinded. Code could be broken, but unclear how frequently this occurred. Subjective outcomes
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Comment: no description of a third‐party outcome assessor. Carried over judgement from blinding of participants and personnel
Incomplete outcome data (attrition bias) All outcomes	Low risk	Comment: intention‐to‐treat analysis used. 2% (N = 1) in trial A withdrew, 5% (N = 3) in trial A lost to follow‐up.
Selective reporting (reporting bias)	Unclear risk	Comment: no protocol identified. All prespecified outcomes from methods appear in results.
Other bias	Unclear risk	Comment: some children were not enrolled when the emergency department was busy, potential to bias participant selection.
Overall risk of bias All outcomes	Unclear risk	Comment: at least 1 domain judged as unclear risk, and no domains judged as high risk.