Response to comment on: Davidson MB (2007) The dilemma of self-monitoring of blood glucose. Diabetologia 50:497–499

To the Editor: After several long discussions at meetings concerning self-monitoring of blood glucose (SMBG) in diabetic patients not taking insulin, A. J. Karter and I agree to disagree. I will respond briefly to the points raised in his letter [1]. As stated in my Commentary [2], observational studies can be compromised by self-selection and issues of confounding. Although a few of them have shown a benefit of SMBG in terms of glycaemic control, most have not [3]. Regarding the ‘select’ randomised clinical trials (RCTs), five of the nine did not find an association, and serious design flaws in the remaining four invalidated (in my view) the conclusion that SMBG per se was responsible for the lowered glycaemia. Although the two meta-analyses found overall changes in HbA1c of −0.3% [4] and −0.4% [5] in those that performed SMBG, the authors stated that the methodological quality of the studies was limited [4] and that there was either a moderate or high risk of bias in the studies reviewed [5]. The reference [6] citing the importance of behavioural interventions deals mainly with the untranslatability of positive, tightly controlled efficacy trials into messier, realworld effectiveness studies. One problem with this argument is that, to date, the efficacy trials of SMBG in diabetic patients not taking insulin have produced negative results. Based on the overwhelming evidence that lowering glycaemia ameliorates the microvascular complications of diabetes, we first need to demonstrate this outcome before dealing with the valid issues that impede its translation. I do agree that SMBG values have no direct effect on glycaemia [1]; appropriate action leading to better control based on these results is necessary. However, as pointed out previously [2], immediate actions in patients not taking insulin are limited and longer term behavioural changes have, for the most part, not materialised. The two references cited to imply that performing SMBG may enhance the ability of patients to make appropriate behavioural decisions [7, 8] may not be particularly germane. In one [7], which included patients who did and did not take insulin, changes in HbA1c were −0.13% in those performing SMBG after receiving intensive instruction, −0.04% in those performing SMBG after receiving standard instruction, and +0.04% in those receiving standard care with no new instruction in SMBG at the start of the study. Significantly more patients in the first group than in the other two groups saw improvements in their HbA1c level. However, as Gertrude Stein is alleged to have said, ‘A difference to be different must make a difference.’ That would certainly not seem to be the case here since this difference would not lead to any change in patient outcomes. In the second study the intervention patients were taught how to use the internet and uploaded their SMBG values at their convenience while the control patients simply visited the outpatient department every 3 months (as did the intervention group) [8]. Most patients were not taking insulin. Regarding the point raised about intensive nurse case management [1], the 40 intervention patients in this study were serviced by three endocrinologists (a professor and two clinical instructors), a nurse and a dietitian. The two clinical instructors logged on to the system daily and sent appropriate recommendations every 2 weeks (based on the Staged Diabetes Management Protocols, with any changes in medication cleared by the professor). Approximately half of the patients logged on to the system more Diabetologia (2007) 50:1567–1568 DOI 10.1007/s00125-007-0691-3