de Brito‐Ashurst 2013.

Study characteristics
Methods	Study design: parallel, open‐label RCT Time frame: June 2008 to July 2009 Duration: 6 month intervention
Participants	Country: UK Setting: tertiary renal unit based in acute care hospital in East London Inclusion criteria: eGFR < 60 mL/min; mean BP > 130/80 mm Hg on at least 2 clinic visits or taking antihypertensive medication; Bangladeshi origin; Attending predialysis clinic Baseline characteristics (mean ± SD) CKD; mean eGFR ± SD (mL/min/1.73 m²): low salt (41 ± 17); high salt (42 ± 15) Mean BP ± SD (SBP/DBP mm Hg): low salt (149 ± 15/85 ± 6); high salt (156 ± 11/85 ± 6) Median number of anti‐hypertensive medications: 3 (range 2 to 4) Mean sodium excretion ± SD (mmol/day): total (261 ± 50); low salt: (263 ± 54); high salt (259 ± 47) Number: low salt (25); high salt (23) Mean age ± SD (years): low salt (56 ± 11); high salt (61 ± 9) Sex (M/F): 28/20 Exclusion criteria: on dialysis; BMI < 20 or > 35 kg/m²; urinary incontinence; cognitive impairment or mental problems impairing ability to participate
Interventions	Low salt group Reduced sodium intake by ongoing individualised dietary education (in person and phone calls) and cooking lessons Duration: 26 weeks High salt group Sodium intake: usual care (general low salt advice sent with doctor's letter) Duration: 26 week Co‐interventions Nil
Outcomes	24‐hour BP Total body water by body composition monitor Measurement of sodium intake: 24‐hour urine Measurement of confounders 24‐hour urinary potassium and creatinine Body weight change Physical activity levels measured using a pedometer
Notes	Additional data: provided by authors. Trial registration: https://clinicaltrials.gov/ct2/show/NCT00702312
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "Randomisation to treatment was conducted by the study statistician using computer‐generated random blocks with block sizes between four and eight"
Allocation concealment (selection bias)	Unclear risk	Quote: "Group assignment given to the researcher" Further information not provided
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Unblinded; objective outcomes unlikely to be affected by performance bias; dietary behaviour may have differed due to lack of blinding
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Outcomes were objective and not immediately available, analysis was performed blinded. Quote: “Neither participants nor the dietitian administering the intervention could be blinded to treatment allocation. Data analysis was conducted by the study statistician who was blinded to treatment allocation.” Blinding of participants: no, blinding of investigators: no; blinding of outcomes assessors: no, blinding of data assessors: yes
Incomplete outcome data (attrition bias) All outcomes	Low risk	Reasons for attrition unlikely to be related to allocation. 56 participants enrolled; 8 withdrew (14% attrition); unwilling to complete: 24‐hour urine collection (3), BP monitoring (2), attend dietary education (1) lost to follow‐up: death (1); emigration (1) Attrition by allocation: low salt group (3); high salt group (5)
Selective reporting (reporting bias)	Low risk	No evidence of outcomes missing from report
Bias from confounders	Unclear risk	Intervention is described as salt restriction Quote: "in addition to standard hypertension medication management" but unclear whether changes to medication occurred (or were measured) during follow up. Major confounders (potassium intake, body weight change, physical activity) measured and reported as 'unchanged'. Baseline imbalances: Change from baseline reported
Other	Low risk	Funding: PhD scholarship from charitable trust Quote: "this study was funded by a PhD fellowship grant from the trustees of Barts and The London Charitable Foundation. The analysis, interpretation of data, generation of the manuscript and decision to submit for publication were carried out independently of the funding body"