Bergstrom 1986.

Methods	Study design: parallel RCT Study duration: June 1983 to September 1988 Study follow‐up period: More than 200 days
Participants	Country: Sweden Setting: single centre renal outpatient department Patients aged 20 to 70 years with CrCl < 70 mL/min/1.73 m2 and linear progression of CKD; patients were randomised if they demonstrated significant progression of CKD over 12 or 24 months Number (randomised/analysed): low protein diet group (11/7); normal protein intake group (12/9) Mean age ± SD (years): not reported Sex (M/F): not reported Exclusion criteria: treatment with immunosuppressive drugs, corticosteroids or NSAIDs
Interventions	Low protein diet group Prescribed protein intake: 0.55 g/kg/d + essential amino acids 0.1 g/kg/d Calculated protein intake: 0.65 ± 0.18 g/kg/d at end of study Normal protein diet group Prescribed protein intake: unrestricted protein diet Calculated protein intake: 0.86 ± 0.15 g/kg/d at end of study Co‐interventions Interventions to maintain blood pressure < 160/90, bicarbonate ≥ 20 mmol/L and serum phosphate ≤ 1.7 mmol/L
Outcomes	GFR at end of study (Cr‐51 EDTA measurement and CrCl)
Notes	57 participants assessed for eligibility; 23 randomised. 34 excluded (10 had stable kidney function, 8 progressed to ESKD, 3 withdrew before randomisation, 13 still in 12 to 24 month control period to determine progress of CKD) Funding source: not reported Contact with study authors for additional information: no Other: last identified report was an interim report
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Insufficient information to permit judgement
Allocation concealment (selection bias)	Unclear risk	Insufficient information to permit judgement
Blinding of participants and personnel (performance bias) All outcomes	High risk	Not blinded and lack of blinding may influence patient management
Blinding of outcome assessment (detection bias): End or change in GFR End of change in GFR	Low risk	Laboratory measurement of GFR and laboratory measure unlikely to be influenced by lack of blinding
Blinding of outcome assessment (detection bias): Need to start dialysis Need to start dialysis	Unclear risk	No information provided. Need to start dialysis was not recorded as a study outcome
Incomplete outcome data (attrition bias) All outcomes	High risk	30% (7/23) excluded from analysis or lost to follow‐up
Selective reporting (reporting bias)	Unclear risk	Only outcome reported was GFR and unclear what other outcomes planned
Other bias	Unclear risk	Insufficient information to permit judgement