Crivelli 1986.

Methods	Randomised controlled trial Cross‐over design rule = time (2 consecutive days)
Participants	Seven adults (6 male) completed the study Age range 27 to 40 years Asthma severity: asymptomatic Included: patients with documented asthmatic airway obstruction Excluded: pregnant women asthmatic patients with concomitant liver and/or cardiovascular diseases, and patients treated with drugs affecting the hepatic microsomal enzyme system (barbiturates, phenytoin, rifampicin etc.) Prescribed medication: no bronchodilators, sodium cromoglycate or steroids for at least 2 weeks before the investigation Control measures: withheld all caffeine and methyl xanthine‐containing foods and beverages at least 12 h prior to the experiment
Interventions	6 mg/kg caffeine versus placebo. Orange juice drink containing caffeine or a placebo drink containing solvent, i.e. saline. Carbachol challenge
Outcomes	FEV1, SGaw
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	No details
Allocation concealment (selection bias)	Unclear risk	Method of allocation unknown
Blinding (performance bias and detection bias) All outcomes	Unclear risk	Described as "double‐blind" but caffeine or saline given in orange juice so may not have tasted the same
Incomplete outcome data (attrition bias) All outcomes	Low risk	No dropouts