Thiamine in diabetic nephropathy

Keywords Diabeticnephropathy.Microalbuminuria.Thiamine.Type2diabetesAbbreviationsRAAS Renin–angiotensin–aldosterone systemUAE Urinary albumin excretionTo the Editor: We read with great interest the article byRabbani et al. [1], in which the authors present the resultsof the first randomised double-blind placebo-controlled trialof high-dose thiamine for the treatment of microalbumin-uria in patients with type 2 diabetes. Rabbani et al.concluded that treatment with thiamine for 3 monthsresulted in regression of albuminuria. This is a veryimportant finding, possibly leading to the further conclu-sion that high-dose thiamine should be considered as anovel treatment modality for diabetic nephropathy.However, there are several issues in the current studythat cause concern. According to the data presented inTable 1 of the paper, urinary albumin excretion (UAE) inthe intervention group decreased from a median of 43.7 mg/24 h at baseline to 30.1 mg/24 h after 3 months of treatment(a difference of –13.6 mg/24 h). In the placebo group, thecorresponding values were 50.9 mg/24 h and 35.5 mg/24 h(a difference of –15.4 mg/24 h). Changes in UAE are alsopresented in Fig. 1a, with values of about –17 mg/24 h forthe intervention group and about –5 mg/24 h for theplacebo group. Since both outcomes represent the samedata, some clarification would be appropriate. The furtherdecrease in UAE during the washout period in both groupscauses additional concern, as it suggests that factors otherthan thiamine may have contributed to the decrease inUAE.The authors conclude that thiamine is superior toplacebo because of the difference between the medianvalues of UAE after 3 months of therapy. However, in orderto validate this conclusion, some further questions need tobe addressed. Although there was no significant differencebetween the two groups in median UAE at baseline, thisdoes not necessarily mean that there was no impact on theresults [2]. In studies with small sample sizes, imbalancesbetween the two groups can easily occur despite random-isation. It would also be relevant to know whether therewere any differences in the use of angiotensin-convertingenzyme inhibitors and angiotensin receptor blockers be-tween the groups and, if they were used, when thetreatments were started. It should be noted that the effectsof these drugs on UAE may take a long time to becomedetectable.