Is Blood Glucose Testing Worthwhile?

Here we go again: Another study  claiming that self-monitoring of blood glucose levels (SMBG) doesn't help patients with type 2 diabetes. You can see the full text here.

Some previous studies have claimed the same thing, and some even claimed harm from SMBG, namely increased rates of depression or decreased "quality of life," although others claimed benefit.  Most informed patients agree that in order to be effective, patients must be trained in how to interpret the results and take action as a result. If you eat doughnuts and see a high number on your meter after a couple of hours, don't eat doughnuts. Just measuring without using the results to take some kind of action is, most agree, pretty useless and a waste of money.

The authors of the recent study agree: ". . . for SMBG to be an effective self-management tool in non–insulin-treated T2DM, the patient and physician must actively engage in performing, interpreting, and acting on the SMBG values."

In this study, patients were randomly assigned to one of three groups: no testing, testing, or testing with feedback. In the latter group, the feedback was computer-generated, not actual conversations with a human being. Here are examples of the feedback:

Sample Messages for Blood Glucose Values at Goal

• You are right on target. Remember to check your blood sugar tomorrow morning.”
• “Keep up the good work.”
• “Outstanding!”
• “Way to go. Keep checking every morning before breakfast!”
• “Your blood glucose goal is between 70-130 in the morning before you eat. You are doing marvelously.”

Sample Messages for Blood Glucose Values that are Mildly Elevated

• “Keeping track of the foods you are eating and the physical activity you are doing may help you pinpoint reasons why your blood sugars are running high.”
• “This number is a bit off target. Remember to check again tomorrow morning before eating.”
• “Your target in the morning before eating is 70-130.”
• “Staying on track with your diabetes can be tough at times. You can do this! Aim for a target fasting blood glucose value in the morning between 70-130.”

Sample Messages for Blood Glucose Values that are Very Elevated

• “Please discuss with your health care provider to talk about ways to get your blood sugars down to a more healthy range.”
• “Please consider making an appointment with your doctor. Your blood sugars have been too high lately. Your target before breakfast is 70-130.”
• “Time to check in with your primary care provider about these blood sugar numbers. They have been running too high.”

This is certainly better than nothing, but the messages are too general to be of much use and focus on fasting levels. I don't see anything like "Oops. Your numbers were high after this meal. See if you can figure out what it was in the meal that made your numbers go too high."

In fact, I couldn't find in the paper or even supplementary material anything about when patients were told to test, so I asked the corresponding author, Katrina Donahue. It turns out it was not simple. She said,

"The testing was based on once daily testing, but would vary depending on the patient’s blood sugar levels. First, they were instructed to test a.m. fasting blood sugars. When at goal, they were instructed to test a.m. fasting 3-4 times per week and pre bed 3-4 times per week. If still at goal, they were instructed to test a.m. fasting 1-2 times per week and 2 hour post prandial 5-6 times per week."

So only those patients who reached their fasting goals (70-130 mg/dL) were told to test after meals, and it's testing after meals that really tells you how different foods affect your blood sugar numbers, although your fasting levels may give a general idea of your overall control.

One interesting thing in this paper is the graphs showing hemoglobin A1c levels with time and the proportion of patients actually testing when assigned to the testing group. The A1c levels over 12 months are very similar to the results we usually see in diet studies. Initially the intervention is successful, but then, usually after about 6 months, the results slowly revert to baseline.

A similar pattern was seen with the proportion of patients told to test who were actually testing: High compliance at first dropping to about 60% by the end of the year.

I think these graphs show something important. People who are diagnosed with diabetes are at first really upset and are willing to follow some lifestyle change, be it eating less, eating fewer carbohydrates, exercising more, taking expensive drugs, or whatever. But then, with time, the enthusiasm for major changes begins to pall. Temptations seem greater.

The same is often seen with people who diet simply for weight loss. Each new diet promises that they'll look like movie stars, so they're very compliant at first, but then the cheesecake seems more important than fitting into smaller clothing and gradually they revert to former habits and then try some other diet that has the same unrealistic promises.

So the really important question is: How can we deal with this loss of enthusiasm for a new, healthier lifestyle? I don't think getting text messages from faceless health care people will have a tremendous impact long term, although as a non-texter maybe I'm wrong.

I think we need intensive education with real human beings and contact with other people who have diabetes. We don't need individual instruction; classes should work and also let people meet fellow patients they can keep in touch with. Of course, diabetes classes already exist, but too many people have complained that they were pretty useless and focussed on cutting out fat.

We need to study what kind of diabetes education works best. We need to teach people that it's not enough to "watch your diet." As patients, we have to accept that our diet must change in major ways, and that these changes are not short term but for the rest of our lives. I think accepting that is one of the most difficult aspects of having diabetes. Years ago, when I went on a diet to lose weight, I thought that when I reached my goal weight I could then eat like everyone else. Of course if one has a tendency to gain weight, one can't.

In order for dietary changes to  have a major impact, we must accept that we can no longer revert to eating the huge amounts of food usually served at restaurants, and we can no longer eat a lot of cake and cookies. Even "healthy" fruit makes my blood glucose go too high, although I do eat limited amounts of berries. Yes, it's inconvenient, but so is losing your feet or going blind.

We need to teach people that that for most (there are always exceptions) fingerpricks really don't hurt very much. I always laugh when I read popular press articles about some new treatment that they claim will eliminate "painful insulin injections." Insulin injections are even less painful than fingersticks because you inject into areas that aren't very sensitive. The popular press probably doesn't realize that neuropathy is a lot more painful than insulin injections or fingersticks.

The key is real education. Maybe not in the first weeks or so, when most patients are still in shock, but as soon as possible. With real education, we can live a long time with this disease, maybe even longer than we would have lived had we maintained our old habits.

So the health care system should figure out how to teach patients how to test productively rather than just testing. Productive testing is a lot cheaper than treating complications.

With time, the frequency of testing can decrease as we learn what we can eat and what we should avoid. I've had type 2 for more than 20 years, and I had a continuous glucose monitor for about a year (thanks to a generous friend), so I have a pretty good idea of what works and what doesn't and now do only spot checks to make sure my control hasn't deteriorated. Without all this information I might now have serious complications that would be expensive to treat.

Testing works when done correctly. Let's find out the best way to teach it.