Just Plain Wrong

My current rotation has me working days and nights and switching between them often. Today I was taking a nap when I woke to 6 missed calls from my wife. I managed to answer the 7th to find my wife was coming home from work. “Why?” I asked her. She told me her Dexcom Follow app showed that I was at a blood sugar of 44 and without hearing from me, she feared the worst. I assured her I was fine and that this was incorrect. Looking back, I should have tested to see what it was but I am positive it was not that low. Thankfully I have not lost the ability to sense hypoglycemia at this point and my wife is keenly aware when I seem off. She has seen me with measured blood glucose values from 450 to 23.

While my wife loves being able to see exactly where my blood sugar is in real time, I really like the trend arrow telling me where I am heading and how fast I’m heading there.  Knowing if I am going down slowly or quickly is very good to differentiate. Unfortunately I have grown to realize I can’t take the CGM numbers as 100% accurate. A few weeks ago I had trouble getting my blood sugar down most of the day. Before I went to bed my CGM said I was “high” meaning >400. I took a large correction dose of insulin and checked my glucometer as well. I was actually at 214. Too much time had passed to cancel the insulin bolus but I was able to set a 0% insulin delivery rate for the next several hours. Avoiding hypoglycemia, I was able to rest with no issues. Problems like this happen often. My CGM tells me I am high, low, or at a good value only to find out later that this is just plain wrong. While the numbers are often incorrect, the arrow is always correct so I still see benefit to continuing its use.

Interestingly an research study recently came out confirming this. The ADA Diabetes care journal presented this and the study is summarized here for those who hate reading research journals. Only 6 of 18 tested CGM systems were found to be accurate (within 15% for blood glucose values >100 mg/dL) for all 3 study trials. I have contacted Dexcom about this issue before and while they try helping by replacing sensors, transmitters, and updating the receiving app, the results are always the same. Part of the issue comes from the very basic misnomer.

Blood sugar can only accurately be measured with a sample of blood. The CGM devices measure interstitial fluid (fluid between cells and outside of the circulatory system) glucose and estimate blood sugar values. There is also inherent risk for superficial infection and abscess (I have had both) from leaving any device sticking into your skin for days at a time.  Leaving a device in your blood stream for an extended period of time can have much worse complications and why this is typically done by medical professionals. For now, this is the best option we have and I am still grateful for it.

At the end of the day the life of a diabetic today is better than it was 10+ years ago. I still have my gripes but with wearable technology, we are allowed to make treatment choices on the fly. We can be warned as we are heading for trouble but before we get there. We are still making improvements but it can seem slow at times. Blood, needles, shots, infusion sets, and skin tape are “normal” today  but maybe not in the future. As Scott says in his July 30th blog post, “It is not normal!”

 

-PS-

My wife is a trooper and I really appreciate all she has done for me. She has been with me at some of my best and worst times and without her, I know I would not have survived.  She celebrated a birthday this week so I wish her a very Happy Birthday and thank you!

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