Vitamin D receptor activator and dietary sodium restriction to reduce residual urinary albumin excretion in chronic kidney disease (ViRTUE study): rationale and study protocol.
Optimal albuminuria reduction is considered essential to halting chronic kidney disease (CKD) progression. Both vitamin D receptor activator (VDRA) treatment and dietary sodium restriction potentiate the efficacy of renin-angiotensin-aldosterone-system (RAAS) blockade to reduce albuminuria. The ViRTUE study addresses whether a VDRA in combination with dietary sodium restriction provides further albuminuria reduction in non-diabetic CKD patients on top of RAAS blockade. The ViRTUE study is an investigator-initiated, prospective, multi-centre, randomized, double-blind (paricalcitol versus placebo), placebo-controlled trial targeting stage 1-3 CKD patients with residual albuminuria of >300 mg/day due to non-diabetic glomerular disease, despite angiotensin-converting enzyme inhibitor or angiotensin receptor blocker use. During run-in, all subjects switched to standardized RAAS blockade (ramipril 10 mg/day) and blood pressure titrated to <140/90 mmHg according to a standardized protocol. Eligible patients are subsequently enrolled and undergo four consecutive study periods in random order of 8 weeks each: (i) paricalcitol (2 µg/day) combined with a liberal sodium diet (∼200 mmol Na(+)/day, i.e. mean sodium intake in the general population), (ii) paricalcitol (2 µg/day) combined with dietary sodium restriction (target: 50 mmol Na(+)/day), (iii) placebo combined with a liberal sodium diet and (iv) placebo combined with dietary sodium restriction. Data are collected at the end of each study period. The primary outcome is 24-h urinary albumin excretion. Secondary study outcomes are blood pressure, renal function (estimated glomerular filtration rate), plasma renin activity and, in a sub-population (N = 9), renal haemodynamics (measured glomerular filtration rate and effective renal plasma flow). A sample size of 50 patients provides 90% power to detect a 23% reduction in albuminuria, assuming a 25% dropout rate. Further reduction of residual albuminuria by combination of VDRA treatment and sodium restriction during single-agent RAAS-blockade will justify long-term studies on cardiorenal outcomes and safety.



NTR2898 (Dutch trial register).
Department of Internal Medicine, Division of Nephrology, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands.
Charlotte A
CA
Keyzer
Department of Internal Medicine, Division of Nephrology, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands.
Maarten A
MA
de Jong
Department of Nephrology and Institute for Cardiovascular Research, VU University Medical Center, Amsterdam, The Netherlands.
G
G
Fenna van Breda
Department of Nephrology and Institute for Cardiovascular Research, VU University Medical Center, Amsterdam, The Netherlands.
Marc G
MG
Vervloet
Department of Internal Medicine, Division of Nephrology, ZGT Hospital, Almelo, The Netherlands.
Gozewijn D
GD
Laverman
Department of Internal Medicine, Division of Nephrology, Medical Center Leeuwarden, Leeuwarden, The Netherlands.
Marc
M
Hemmelder
Department of Internal Medicine, Division of Nephrology, Martini Hospital Groningen, Groningen, The Netherlands.
Wilbert M
WM
Janssen
Department of Clinical Pharmacy and Pharmacology, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands.
Hiddo J
HJ
Lambers Heerspink
Department of Internal Medicine, Division of Nephrology, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands.
Gerjan
G
Navis
Department of Internal Medicine, Division of Nephrology, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands.
Martin H
MH
de Borst
D000419:Albuminuria / Q000209:etiology / Q000628:therapy*; D000806:Angiotensin-Converting Enzyme Inhibitors / Q000627:therapeutic use; D002985:Clinical Protocols / Q000592:standards*; D002986:Clinical Trials as Topic / Q000379:methods*; D004039:Diet, Sodium-Restricted; D006801:Humans; D051436:Renal Insufficiency, Chronic / Q000150:complications*; D012107:Research Design
D000806:Angiotensin-Converting Enzyme Inhibitors
albuminuria; paricalcitol; randomized-controlled trial; sodium reduction