Kobayashi 1996.

Methods	Study design: parallel, 2‐arm quasi‐RCT Time frame: April 1972 to December 1983 (patient diagnosis) Duration of follow‐up: 10 years
Participants	Setting: single renal unit Country: Japan Inclusion criteria: primary diagnosis of IgAN, proteinuria between 1 to 2 g/d; CrCl ≥ 70 mL/min; histological severity score ≥ 7 Number (analysed/randomised): treatment group (20/31); control group (26/59) Mean age ± SD (years): treatment group (30 ± 7); control group (33 ± 10) Sex (M/F): treatment group (12/8); control group (12/14) Exclusion criteria: not reported
Interventions	Treatment group Prednisolone: 40 mg/d for 3 weeks, 30, 25 and then 20 mg/d for 8 weeks; maintained at 15 mg/d for 6 months and then further tapered (most of the patients received steroid therapy for 18 months) Antithrombocyte drugs were prescribed after discontinuation of steroid therapy until final observation Control group Antithrombocyte drugs until final observation Co‐interventions Not reported
Outcomes	ESKD CrCl Urinary protein excretion
Notes	Funding: supported by grants from the Ministry of Health and Welfare, Japan Trials registration identification number: not applicable
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	High risk	Prospectively divided into two groups according to the order of renal biopsy
Allocation concealment (selection bias)	High risk	Prospectively divided into two groups according to the order of renal biopsy. This is a quasi‐randomised study design
Blinding of participants and personnel (performance bias) All outcomes	High risk	Open‐label study
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	High risk	11/31 patients in the treatment group and 33/59 patients from the control group were excluded from the analyses
Selective reporting (reporting bias)	High risk	Key outcomes expected for this type of study (death (any cause), malignancy, infection) were not reported
Other bias	High risk	The participants received differential prescribing of anti‐thrombotic drugs during follow‐up. There was imbalance in sex and history of hypertension at baseline