Primary Care Corner with Geoffrey Modest MD: Glucometers Lower A1c’s in Non-Insulin Using Diabetics, a Little

By Dr. Geoffrey Modest

BMJ just published a meta-analysis of randomized controlled trials (RCTs), finding that non-insulin using diabetic patients who self-monitored their blood sugars had improved glycemic control (see doi:10.1136/bmjopen-2015-010524 ). This analysis included several new studies, not available in prior reviews.

Details:

• 15 RCTs were identified with 3383 patients
• Results:
  • Those using SMBG (self-monitoring of blood glucose) had:
    • Lower HbA1c by −0.33 (−0.45 to −0.22); p<0.001 [the quality of evidence was rated as moderate]
    • Lower BMI by −0.65 (−1.18 to −0.12); p=0.02 [the quality of evidence was rated as low]
    • Lower total cholesterol (TC) by −0.12 (−0.20 to −0.04); p=0.003 [the quality of evidence was rated as high]
    • Lower waist circumference by -2.22 (-4.40 to -0.03); p=0.047 [no comment, but i assume that is in centimeters; the quality of evidence was rated as moderate]
    • No significant difference in fasting plasma glucose, systolic or diastolic BP, HDL, LDL, triglycerides, or weight
    • Subgroup analyses: no difference if Asian countries or US/Europe; A1C was improved in both short-term (<6 month, by -0.36%) or long-term studies (>12 month, by -0.28%). BMI and TC changes were only significant in the <6 month group. and though waist circumference was improved overall, it was not significantly improved in the subgroups, but was near-significant (p=0.06) only in the >12 month group (by -3.15); also similar A1C reductions were found in patient with newly diagnosed type 2 diabetes (T2DM) vs duration >12 months [no further analysis for really long-termers]; SMBG was significantly more effective in patients with lower A1C (<8%) vs higher
  • Adverse events: most common was the incidence of hypoglycemia (higher in SMBG group), though their rate (episodes/patient) was lower

Commentary:

• Prior concern about SMBG reflect its high cost (21% of diabetic prescription costs in the US) and several studies suggesting its lack of efficacy in non-insulin using T2DM patients (e.g. Farmer AJ BMJ 2012;344:e486), even though currently 63.4% of T2DM use SMBG daily
• The analysis, as with pretty much all meta-analyses, is limited by the quality of the studies included, their size, differences in methodology in general, degree of patient education, frequency of testing, and inherent biases associated with the more intensive medicalization in those doing SMBG
• The decrease in A1C of -0.33% is often not considered to be clinically significant (typically defined as a change of 0.5%)
• So, this study does suggest efficacy of SMBG monitoring, albeit perhaps of marginal clinical significance. As an intervention, it does medicalize patients much more than just taking a pill. And this has the potential for both positive and negative effects: the positive side is that it may empower patients in involving them more in taking ownership and treating their condition, and for some patients, this involvement might be important in helping them deal psychologically with a potentially devastating disease; the negative side is that for some patients it might create lots of anxiety and perhaps over-focus/dwelling on their medical problems and perhaps reinforce a more passive, “sickness” mentality which could decrease their ability to function.
• This last difference exposes one of the contradictions of RCTs: they look at a large group of individuals, with some exclusions, but cannot really replicate the actual patient one is treating. It may well be that some patients who want to control their bodies and illnesses more, actually do much better with SMBG than decreasing their A1C by the 0.33% as above, perhaps using the daily blood sugar feedback as a motivation for more lifestyle changes (and, even if the A1C does not plummet, these lifestyle changes might have much broader healthful consequences). Others who may become more anxious or are not interested in this level of involvement, may get no benefit, or the experience might actually be negative. And the sum of these patients in the larger RCTs may then reveal only a mediocre outcome, obscuring the potential benefit for perhaps a lot of people. The real trick might be to figure out who is motivated by the SMBG and use this tool to help them with their diabetes management. And perhaps not using or stopping SMBG in those who do not really benefit. So, yet again, one size just does not fit all….