It was only a Powerpoint slide, but it was the scariest thing I ever saw in my life. The slide showed a blood sugar trend line from a continuous glucose monitor (CGM), not very different from the ones I've seen myself time and time again from my own gear. It showed a hypo that ended badly.

Very badly.

As I soon learned, the power point slide was a post-mortem download. The man wearBlindfoldeding the CGM died. Why didn't the CGM wake him up and warn him? Because it couldn't. It was a "blind" professional CGM that only recorded data without reporting it in real-time.

I was in a hot crowded room at a medical conference, but the slide gave me a cold chill.

But the slide also introduced me to a very real controversy that's dividing the medical community, and highlighting a deeper underlying issue: Should people with diabetes always have access to their diabetes data and be able to react, or is it better at times to "fly blind" and leave the data-based decision-making in the doctor's hands?

That debate is now taking center stage again, as Dexcom makes headlines about its newest "professional" CGM.

In June, the California-based CGM company trumpeted news that it had received FDA approval of the "first and only" real-time professional CGM system for use by clinicians: the Dexcom Professional G4 Platinum. The announcement is good news, but left me reflecting on that frightening slide and probably made some in the patient community scratch their heads, wondering what this "professional" CGM is all about.

After all, the "un-professional" personal CGMs that many of us have access to in our daily lives now have been giving us real-time feedback since 2005 -- and btw, I've used most of them.

Going Pro

The Pro CGM isn't anything extra-special or better than what we use. It's simply a CGM owned and operated by a doctor's office or clinic that's FDA approved for use in multiple patients, rather than single-patient use as personal CGMs are aimed at. Typically, these Pro systems are used for short "studies" that range from several days to a week before you return it to the doctor's office so they can go over the data.

Up until now, all of these professional systems have been retrospective, or "blinded," meaning they record blood sugar data in real-time but are configured to only show this data after the fact to an authorized doctor -- not to you, the one wearing the device.

Actually, all CGMs were originally blind, starting with the first Medtronic system that gotMedtronic iPro2 Professional CGM FDA approval in 1999 and the three newer MedT versions since then. Dexcom's Seven Plus Pro is no longer on the market, so docs currently have two options available: the Medtronic iPro2 and the G4 Platinum Pro. Through the years, what's changed most significantly is simply that CGMs configured for patients to see their own data in real-time have become much more common.

Dexcom's new product is its second foray into the professional CGM front, and while the company's bragging about the real-time capabilities, it's kept a toe in the retrospective waters by adding the option for doctors to blind the CGM use when that's considered to be "clinically necessary."

Dexcom's VP of Strategic Marketing Steve Pacelli tells us the company chose to offer the Dexcom G4 Professional CGMblind option because, at the time they filed for professional indication for the G4 system a year ago, there was still a demand for it. In his words: "there were still some clinicians who were not necessarily believers in real-time CGM."

A year later, Pacelli says that even fewer fit that bill and he expects that most of the Pro G4s systems will run in real-time mode.

Still, Dexcom's decision to keep the blind option is the very issue that splits the medical community.

Real-Time or Retrospective?

One clinician who apparently still backs blind CGM use is Dr. James Thrasher of the Arkansas Diabetes & Endocrinology Center. He started using CGM technology back in the 90s, with Medtronic's CGM System Gold that's considered the granddaddy of all CGMs. In fact, Dr. T still has a pair of them he jokingly offered to sell me.

Currently, he's running 20 of the Medtronic iPro2 units, the company's top-of-the-line retrospective CGM, and he still has some functioning iPro originals from the 30 he bought years ago. Thrasher estimates he runs an average of 10 CGM studies every week.

Thrasher strongly believes in the difference between what he terms "A1C control" and "actual control" -- his way of saying that just having a good A1C is not enough. He says that a within-target A1C results that may be a mix of extreme highs and extreme lows isn't really "control." I actually agree with him on that, but I'm not sure the best way to combat this is by using a blind CGM. I especially disagree with his ideas on who owns the data (isn't it ours?!).

With 90% of his patients being type 2s who Thrasher describes as "poorly controlled," he views blood sugar data as the territory of the doctor. He wants to see what's happening in "normal therapy" (the patients' normal routines) to see what's working and what isn't, and clearly feels that if patients have real-time feedback, they'll react in ways that will prevent him from seeing what normally works or does not.

"You have to know exactly what you are trying to treat," Thrasher says, noting that blind CGM can help him pinpoint that information. He does not want his patients making impulsive changes based on numbers flowing on a screen.

"If they can see the data, they can react to it," he says. "You can't react to what you do not see."

This is the crux of the clinical controversy -- because reacting to blood sugar levels in real-time is the whole point, says the Chief Scientific & Medical Officer of the American Diabetes Association, Dr. Robert Ratner.

"The goal is always for the person with diabetes to make the adjustments they need," Ratner says, pointing out that he feels CGM should be a teaching tool and there's no reason to withhold information from the patient in these days of shared decision-making. Ratner feels that blind CGMs have no role to play in diabetes treatment and should be "limited to clinical investigations in settings with volunteers who have been fully briefed on the potential dangers."

Danger? What Danger?

What, did you forget about my story of seeing that medical conference slide that gave me such a scare? It comes from a case study published by Dr. Robert J. Tanenberg in the Endocrine Practice journal back in 2010. The 23-year-old man's blood sugar went into a free-fall between midnight and 2 a.m., bottoming out at 30 mg/dL with a couple small bumps that investigators believe were regulatory hormone counter-responses that failed.


Sadly, all the retrospective CGM did while all this was happening was sit back and watch him die — while recording the whole thing. That led many people in both the patient and clinical communities to believe that a real-time device could have saved his life. Since then, blind vs. real-time has become a hot topic in the world of diabetes treatment.

As Medtronic has a robust lineup of both real-time and blind CGMs, we reached out to the company's medical director, Dr. Fran Kaufman, for her thoughts about where each type of system belonged. Not surprisingly, Kaufman was quick to support her company's retrospective CGMs. The blind systems are "much more convenient and easy" for both the busy clinician and the patient new to CGM, she said. No mention of danger.

Reaction & Access Opps

Kaufman believes there's no need for real-time feedback in people who can't react in real-time, such as type 2s on oral meds. If there's nothing to adjust, then what's the point of viewing real-time CGM data? Now, I would argue that it's beneficial for anyone to see what various foods do to your blood sugar in real-time, as there's always something that can be adjusted. Heck, just having that knowledge gives you better insight into how you eat and manage your health. But who am I to argue with the likes of Fran Kaufman?

As to office training on CGMs, Kaufman says many docs feel that blind CGMs are more practical, because many practices just don't have the resources to train patients on real-time devices.

"Convenience far outweighs the brownie points of real-time," she said.

The American College of Clinical Endocrinologists (AACE) agrees, writing in their own CGM consensus guidelines, "Since professional CGM requires minimal training and setup time, it may be easier for patients to use than personal CGM."


Of course, the CGM access issue can't be ignored, as patients might not be able to afford or get insurance coverage of their own real-time personal CGM -- especially for those with type 2 or on Medicare. Instead, they might opt for a short-term use of a professional CGM. Getting reimbursement to be part of Pro CGM studies at a doctor's office, which Dexcom's Pacelli says can range from $300 to $400, can be a much easier and more appealing than fight you'd have to put up, and the much larger bill you'd have to foot for a real-time personal CGM.

Still, it's a new game now that Dexcom's G4 Pro becomes the first FDA-cleared CGM that offers real-time functionality and be used in these clinical office settings. What will happen next? Will real-time Pro studies become the de facto standard, or will blind mice still rule the day?

It may depend on the doctor, so choose yours wisely.

Meanwhile, Ratner continues to disagree with those physicians who favor blind CGM use for ongoing diabetes treatment.

"In my mind the value of CGM is to provide the patient immediate feedback," he said, rather than to provide information solely to the physician. He believes patients, doctors, and educators need to work together as a team.

"Physicians are no longer allowed to be paternalistic," Ratner says. "It didn't work 30 years ago, and it doesn't work today."

Disclaimer: Content created by the Diabetes Mine team. For more details click here.


This content is created for Diabetes Mine, a consumer health blog focused on the diabetes community. The content is not medically reviewed and doesn't adhere to Healthline's editorial guidelines. For more information about Healthline's partnership with Diabetes Mine, please click here.