Kawamura 2014.

Methods	Study design: parallel, 2‐arm RCT Time frame: April 2005 to March 2010 Duration of follow‐up: 12 months
Participants	Setting: multicentre (18 sites) Country: Japan Inclusion criteria: biopsy‐proven IgAN; aged 10 to 69 years; urinary protein excretion 1.0 to 3.5 g/day; SCr ≤ 1.5 mg/dL; a histological grade diagnosed as a relatively good prognosis, a relatively poor prognosis, or a poor prognosis in the classification proposed in 2004, and SBP < 140 mmHg and DBP < 90 mmHg Number (analysed/randomised): treatment group (33/40); control group (39/40) Mean age ± SD (years): treatment group (36 ± 13); control group (40 ± 13) Sex (M/F): treatment group (17/16); control group (18/21) Exclusion criteria: nephrotic syndrome; SCr of > 1.5 mg/dL, recent treatment with corticosteroids and/or immunosuppressive agents, and contraindications for general anaesthesia and/or tonsillectomy as assessed by otolaryngologists
Interventions	Treatment group Patients underwent tonsillectomy and subsequently received 0.5 g/day of IV methylprednisolone for 3 consecutive days at 1 to 3 weeks later and then at 2 and 4 months later Control group Steroid pulse therapy only Co‐interventions Oral prednisolone at a dose of 0.5 mg/kg every other day for 6 months
Outcomes	Percentage decrease in urinary protein excretion from baseline Frequency of the disappearance of proteinuria and/or haematuria 12 months after the initial treatment Change in GFR Doubling of SCr from baseline 50% decrease in eGFR from baseline KRT Adverse effects
Notes	The study was supported in part by a Grant‐in‐Aid for Progressive Renal Diseases Research (Research on Intractable Disease) from the Ministry of Health, Labour and Welfare of Japan
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Randomisation was done by a technical assistant in the registration centre using a computer‐based allocation program with a minimisation method, which was developed by an outside company
Allocation concealment (selection bias)	High risk	Allocation was based on the presence or absence of tonsillectomy
Blinding of participants and personnel (performance bias) All outcomes	High risk	Since the allocation was based on the presence or absence of tonsillectomy, neither the patients nor the physicians were blinded to the group assignment
Blinding of outcome assessment (detection bias) All outcomes	High risk	Although those assessing the outcomes were not blinded, they assessed the data regarding the pre‐defined outcomes using pre‐specified statistical analyses. Key outcomes were objective laboratory measures and were unlikely to be affected by any knowledge of treatment allocation. Reporting of adverse events may have been influenced by knowledge of treatment allocation
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Insufficient information to permit judgement
Selective reporting (reporting bias)	High risk	Key outcomes expected for this type of study (death (any cause), infection) were not reported
Other bias	Low risk	The study appeared to be free of other sources of bias