Eden 1967.

Methods	Randomised double‐blind controlled trial
Participants	Study period: not reported Setting: hospital in USA Inclusion criteria: children hospitalised with acute croup, including those presenting with acute respiratory infections characterised by barking cough, hoarseness, sternal retractions, and respiratory stridor Exclusion criteria: not reported Baseline demographics (N = 50): proportion male: treatment: 60%; control: 80% age in years (%): treatment: 68% 0 to 2 years, 28% 2 to 4 years, 4% > 4 years; control: 56% 0 to 2 years, 28% 2 to 4 years, 16% > 4 years croup score: not reported
Interventions	Treatment (N = 25): 0.1 mL/kg per dose schedule (0.1 mg/kg) intramuscular dexamethasone every 6 hours for 48 hours (total daily dose of 0.40 mg/kg) Control (N = 25): volume of 0.1 mL/kg per dose schedule of placebo (control) preparation intramuscularly every 6 hours for 48 hours
Outcomes	Patient improvement at 6, 12, 24 hours; tracheostomy
Notes	Funding source: dexamethasone (Decadron) by Merck Sharp & Dohme
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "The patients were divided into two groups according to a table of random sampling"
Allocation concealment (selection bias)	Unclear risk	Comment: insufficient information provided to judge.
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Quote: "double blind" "The composition of each preparation was unknown to the investigators until the end of the study"
Blinding of outcome assessment (detection bias) All outcomes	Low 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: no missing outcome data
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.