The American Diabetes Association 73rd Scientific Sessions: Type 1 Diabetes (Continued)
A Comparison of Three Top Continuous Glucose Monitors
An accurate continuous glucose monitor (CGM) is one of the key building blocks of an artificial pancreas, and many have said that it is one of the biggest barriers to such a system gaining FDA approval. We were therefore glad to see Dr. Steven Russell (Massachusetts General Hospital, MA) and his colleagues directly compare the accuracy of three CGMs: the Dexcom G4 Platinum, the Abbott FreeStyle Navigator (currently only available out- side the US), and the Medtronic Enlite (currently only available outside the US, with FDA approval expected by the end of 2013 according to Medtronic). What was cool about this study was its design: every patient wore all three CGMs at the same time, meaning results could really be compared in a head-to-head-to-head fashion. Wow!
A CGM's accuracy is measured by its mean absolute relative difference (MARD) from reference blood glucose levels, and a lower value means the sensor is more accurate. Of these three CGMs, Dexcom's G4 Platinum was the most accurate sensor, with a MARD of 10.8%. The Abbott FreeStyle Navigator came in slightly behind at 12.3%, with the Medtronic Enlite at 17.9%. Though these results were encouraging for Dexcom and Abbott, Dr. Russell noted that CGM calibration errors are still a problem – he showed data where improper calibration (e.g., entering the wrong blood glucose value due to human or glucose meter errors) caused poor readings for an entire day. He said that calibration is still the "Achilles' heel" of CGM technology, and that it will be a critical area to improve.
DCCT & EDIC: Thirty Years of Type 1 Diabetes Data
This year's ADA marked a major anniversary, as the Diabetes Control and Complications Trial (DCCT) turned 30 years old. Begun in 1983, the trial investigated whether tight glucose control actually matters. Patients were randomized to either intensive glucose control or conventional therapy, were followed for an average of 6.5 years, and assessed for their risk of complications. As so many people remember, the study's initial results in 1993 showed absolutely striking results – there were very significant reductions in eye, kidney, and nerve complications by as much as 76%. While after the initial trial finished, the participants in both groups gravitated together and their glucose control became similar, the positive impact of tight glycemic control was absolutely clear. The follow-up observational study, the Epidemiology of Diabetes Interventions and Complications (EDIC) has tracked participants for the last two decades to study how earlier tight control affects complications long-term. Based on the brand-new, long-term EDIC data, those who originally received intensive therapy continue to show striking benefits: a 50% reduced risk of impaired kidney function, nearly 60% reduced incidence of heart disease and stroke, and 50% less need for ocular surgery to deal with eye-related complications.
As for why there continues to be such clear differences in complications between the DCCT/EDIC's intensive and the conventional therapy populations – even 20 years after the end of the original interventions – may speak to some form of long-term "metabolic memory. In other words, improvements in A1c today can have very real effects years onward. It's still an open question just how that works, but the key takeaway, as Dr. David Nathan, the leader of this landmark study put it, is that "there's no point of no return with A1c."
One unexpected negative finding in the latest EDIC data is a previously under-recognized diabetes complication. Cheiroarthropathy, popularly known as frozen shoulder, involves the progressive stiffening of tissues around joints, also leading to carpal tunnel syndrome or trigger fingers. It was found that two-thirds of DCCT participants showed signs of this condition and it wasn't any better for those with tighter control – depressingly! Frozen shoulder is quite common in the general population as people get older, and that fact may have obscured the link between the complication and diabetes in the past.
The most disappointing part of the DCCT/EDIC data announcement was that there is new data on mortality that has been embargoed for publication purposes. We will report on this as soon as possible – as we understand it, now that there have been 50 deaths, the data on mortality can be unveiled. We're thinking this data will be truly compelling and helpful for understanding the long-term effects of intensive blood sugar control – and we're going to just have to wait a little bit longer!
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NOTE: This information is not intended to be a replacement or substitute for consultation with a qualified medical professional or for professional advice related to diabetes or another medical condition. Please contact your physician or medical professional with any questions and concerns about your medical condition.
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