Medici 1993.

Methods	Randomised placebo‐controlled cross‐over study. .
Participants	18 patients recruited (4 excluded during run‐in due to poor compliance). Study group 14(9 men, 5 women). Age range 20 to 65 years. They had stable atopic asthma and fulfilled the ATS criteria for the diagnosis of asthma. Exclusion criteria: instability of asthma, therapy with oral steroids, cromoglycan or diuretics, cardiac insufficiency, arrhythmias, liver diseases, kidney diseases, diabetes mellitus, smoking and pregnancy.
Interventions	After 2 weeks on a low sodium diet (86 to 103 mmol/day), given 157 mmol of sodium daily (in the form of sodium chloride) or placebo for 3 weeks. Then the 2 groups were crossed over for a second 3‐week treatment period (sodium citrate with 154 sodium mmol). There was no washout period.
Outcomes	PD20, FEV1, FVC, PEFR x 3 a day, inhaler bronchodilator and corticosteroids sprays, number of asthma attacks
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	No information given.
Allocation concealment (selection bias)	Unclear risk	Described as randomised; no information given.
Blinding (performance bias and detection bias) All outcomes	Unclear risk	Described as blind, however the papers states that due to side effects when on the salt tablets, less than intended amount was used.
Incomplete outcome data (attrition bias) All outcomes	Low risk
Selective reporting (reporting bias)	Unclear risk	Not clear from information given.
Other bias	Unclear risk	Subjects had heartburn on the sodium tablets and so could have been unblinded. Subjects changed medication from regular to prn and there was no wash‐out period. No calculation of power described.