To the Editor: We have a number of questions regarding the randomized controlled trial by Dr House and colleagues.1 First, at baseline, the B-vitamin group had a higher percentage of peripheral vascular disease compared with the placebo group (20.2% vs 14.3%), which may have contributed to higher vascular events in the vitamin B group.
Second, inclusion criteria for this study were any diabetic patient with albuminuria greater than 300 mg per day and stage 2 or 3 chronic kidney disease. Rate of progression of chronic kidney disease is more rapid in stage 3 compared with stage 2,2- 5 so effects of B-vitamin supplementation could be different in the 2 subgroups. We would like to see the hazard ratios stratified by chronic kidney disease stage at baseline.
Kadam S, Kulshrestha S, Swaminathan S. B-Vitamin Therapy for Diabetic Nephropathy. JAMA. 2010;304(6):636-637. doi:10.1001/jama.2010.1105