Welch 1992.

Methods	Study design: cross‐over, 2‐arm RCT Time frame: 1983 to 1989 Duration of follow‐up: 24 weeks
Participants	Setting: single centre Country: USA Inclusion criteria: children with IgAN Number (analysed/randomised): 20/20 Mean age: 13 years (SD not reported) Sex (M/F): 15/5 Exclusion criteria: SCr ≥140 µmol/L; hypertension (BP consistently 99th percentile for age and gender)
Interventions	Two, 3‐month courses of therapy separated by a 3‐month rest period Treatment group Prednisolone: 2 mg/kg/day for 2 weeks, then every other day for 10 weeks Control group Placebo: 2 mg/kg/day for 2 weeks, then every other day for 10 weeks Co‐interventions Not reported
Outcomes	Urinary protein excretion SCr
Notes	Funding: not reported Trials registration identification number: not applicable
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "The first course for each patient was assigned by a random‐numbers table."
Allocation concealment (selection bias)	Unclear risk	Insufficient information to permit judgement
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Quote: "The drugs were dispensed by the Children's Hospital Medical Center pharmacy with a coded label, so that neither patients nor investigators were aware of the identity of the medication."
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Blinding of outcome assessment not specifically reported. Key outcomes were objective laboratory measures and were unlikely to be affected by any knowledge of treatment allocation
Incomplete outcome data (attrition bias) All outcomes	Low risk	All participants were included in analyses
Selective reporting (reporting bias)	High risk	Relevant numeric data were not available. Patient‐centred outcomes of relevance were not reported
Other bias	Unclear risk	Insufficient information to permit judgement