DUAAAL 2011.

Study characteristics
Methods	Study design: double blind, cross‐over RCT Time frame: April 2006 to October 2009 Study duration (weeks): total (30); run‐in (6); interventions (6); no washout
Participants	Country: the Netherlands Setting: multicentre; outpatient clinics (3) Inclusion criteria: consecutive patients with kidney disease who visited the nephrology outpatient clinic with non‐diabetic kidney disease (confirmed by analysis of blood and urine or kidney biopsy); CrCl ≥ 30 mL/min; BP > 125/75 mm Hg; residual proteinuria > 1.0 g/day with ACEi at maximal dose (lisinopril 40 mg/day); aged > 18 years Baseline characteristics CKD (eGFR): not reported Mean BP ± SD (SBP/DBP): 131 ± 18/71 ± 12.5 mm Hg Mean sodium excretion ± SD: 177 ± 74 mmol/day Number: randomised (54); analysed (52) Mean age ± SD: 51 ± 13 years Sex (M/F): 43/9 (83% male) Exclusion criteria: SBP > 180 mm Hg or DBP > 110 mm Hg; diabetes; renovascular hypertension; decrease in CrCl by ≥ 6 mL/min in previous year; cardiovascular event in the previous 6 months; immunosuppressive treatment; regular use (> 1 day/week) of NSAIDs; pregnancy or breastfeeding
Interventions	Low salt group Target sodium intake: 50 mmol/day (individualised counselling by dietician) Duration: 12 weeks High salt group Sodium intake: usual diet Duration: 12 weeks Co‐interventions Each participant was on lisinopril 40 mg/day for entire study  and went through four interventions for six weeks each in random order (*used for analysis) Usual salt, placebo* Usual salt valsartan 320 mg/day High salt, placebo* High salt valsartan 320 mg/day Other information Run‐in: 6 weeks; no dietary intervention No other RAAS blockers. Additional antihypertensive drugs such as beta‐blockers, alpha‐blockers, calcium channel blockers, and diuretics were allowed and kept stable during the study
Outcomes	24‐hour proteinuria Clinic BP (supine) Clinical evaluation of oedema Weight Serum markers (electrolytes, lipids, proteins, creatinine) Urinary electrolytes and CrCl Measurement of sodium intake: 24‐hour urine Measurement of confounders Medication intake measured by pill counts (not relevant to dietary interventions) Protein intake measured from urea excretion (Maroni formula)
Notes	Trial registration: http://www.isrctn.com/ISRCTN50137410 Additional data: provided by authors
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "An independent pharmacist randomised these sequences, using a computer program”
Allocation concealment (selection bias)	Unclear risk	Insufficient information to permit judgement
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Dietary interventions were open label but outcomes were objective and unlikely to be influenced by performance bias
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Insufficient information to permit judgement
Incomplete outcome data (attrition bias) All outcomes	Low risk	Quote: "Additionally, we analysed the data for all 54 patients who were included (intention to treat). As the effect estimates and confidence intervals were very similar and the statistical and clinical conclusions did not change, we have not shown these data" 54 randomised, 2 withdrew after randomisation; 52 included in analysis
Selective reporting (reporting bias)	Low risk	Study was pre‐registered online and the pre‐specified outcomes were reported
Carry‐over effect	Low risk	Adequate intervention duration to reduce risk of carry‐over effect
Bias from confounders	High risk	Medication changes reported and did not occur during placebo phases. Comparison of usual intake versus low sodium intervention increases risk of dietary confounders ‐ reduction in body weight, potassium excretion and urinary urea in low salt phase suggests potential confounding
Other	Unclear risk	Funding: study supported by Novartis; declaration of non‐involvement by funder Quote: "Funding: Unrestricted grant from Novartis. No role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; and preparation, review, or approval of the manuscript"