The Value of Self-Monitoring of Blood Glucose Free

The issues surrounding self-monitoring of blood glucose (SMBG) are interesting and complex. Recently published American Diabetes Association (ADA) Position Statements (1–3) encourage the use of SMBG in all diabetic patients and urge governments and other payers to meet the cost. Until 6 months ago, however, reliable data to support these views in patients with type 2 diabetes have not been available.

At first sight, the recent report by Franciosi et al. (4) appears to make conclusions contrary to the ADA Position Statements, but closer examination reveals this not to be the case. Franciosi studied 2,855 patients with type 2 diabetes recruited from 204 different centers. Different methodologies for HbA_1c measurement were adjusted for mathematically, whereas statistical methods were used for adjusting between different treatment regimes and for between-center variability (the latter accounting for 27% of the differences in the results between groups). In non-insulin-treated patients, Franciosi et al. found that there was a nonsignificant 0.2% increase in HbA_1c levels between no SMBG and infrequent (<1/week) SMBG testing, with a further increase of 0.3% in HbA_1c levels in patients who tested at least daily.

However, the study was not designed to determine the causality of these differences. The authors state that “a higher frequency of SMBG was related to higher HbA_1c levels, thus suggesting that patients with poor metabolic control have a greater tendency to self monitor.”

Contrary to the implication of the concluding sentence of the abstract, this paper presents no data to detract from the extension of SMBG to patients with non-insulin-treated type 2 diabetes.

A few months earlier, Karter et al. (5) published the results of a 24,312-patient study performed by Kaiser Permanente. In contrast to the study by Franciosi et al., in this study all patients were health maintenance organization members following the same treatment protocols and had HbA_1c levels that did not need adjustment. They were randomized by design into treatment groups before statistical analysis. Treatment groups were type 1 diabetic patients (n = 1,159), insulin-treated type 2 diabetic patients (n = 5,552), type 2 diabetic patients on oral treatments (n = 12,786), and type 2 diabetic patients using dietary measures only (n = 4,815). In addition to these study size and design benefits, Karter et al. also had a control group of 24,302 patients who could not be included in the main study.

Within each treatment group, Karter et al. found clinically significant decreases of 0.7% in HbA_1c levels in patients who used daily SMBG compared with patients who did not perform SMBG. Comparison with the control cohort confirmed the results, and the study conclusions remained consistent and significant for each treatment group.

Karter et al. provide good data to support ADA Position Statements to promote the use of SMBG in all diabetic patients, regardless of diagnosis or treatment, and one of the conclusions of Franciosi et al. should remain the goal for all diabetic patients: “Our findings suggest that self-monitoring of blood glucose can have an important role in improving metabolic control if it is an integral part of a wider educational strategy devoted to the promotion of patient autonomy.”