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Pros & Cons of the Tandem t:slim with Control IQ

Tandem t:slim with Control IQ

Tandem t:slim with Control IQ: “Smahtah” than the average pump
By Gary Scheiner MS, CDCES

I’m a big fan of the new smart car (also pronounced “Smaht Cah”) technologies.  What’s not to like?  It’s like having another set of eyes watching the road so that you don’t veer into the wrong lane or bump into the car in front of you.  You still have to be an attentive driver, but as long as you can put up with a few extra beeps, the “smaht” features make driving a whole lot safer.

Today, we’re in the midst of a smaht technology revolution in diabetes management.  Better known as “Hybrid Closed Loop Systems,” or HCLs, they combine an insulin pump, a continuous glucose sensor, and a computer algorithm that adjusts certain aspects of the pump’s insulin delivery automatically.  The result is better overall glucose control (particularly more time spent within one’s target range) and less burden on the user to make all the adjustments on their own.

Until recently, we had two HCL options:

  1. Medtronic’s 670G and a few build-it-yourself system – Loop, Open APS and Android APS.  Medtronic’s system can produce pretty decent glucose control, but it comes with a slew of challenges for the user (see review here: https://integrateddiabetes.com/670g-and-me-insights-and-incites-on-medtronics-latest-system/).
  2. The do-it-yourself systems can produce superior control, but they can be a bear to set up and maintain (see review here:  https://integrateddiabetes.com/loop-vs-medtronic-670g/)

Now, we have something new and, some may say, even smahtah:  the Tandem t:slim pump with Control IQ technology. 

Taking a look at the Tandem t:slim

Tandem’s HCL system features the sleek Tandem t:slim tubed insulin pump with a full-color touch-screen display.  CGM data reaches the pump via Bluetooth signals from the Dexcom G6 sensor, which lasts up to 10 days and requires no calibrations.  Activating the Control IQ algorithm requires the mere flip of a switch and entry of the user’s weight and average daily insulin requirements.  The algorithm predicts where the glucose will be in 30 minutes (based on CGM values and trends) and adjusts the pump’s usual basal delivery based on the predicted value.  The system can also administer conservative correction boluses on an hourly basis if the glucose is predicted to be quite high or remains high.  It has a preset target of 110 mg/dl.

tandem specs

Extended boluses (but not temporary basal rates) remain an option when Control IQ is running.  But the fact is, temp basals are not usually needed since the algorithm makes basal adjustments for the user.  If the user knows that their insulin needs will be significantly higher or lower for a certain period of time, they can easily switch to a different “personal profile,” which includes both basal and bolus settings.  The system has two optional overrides:  An exercise setting (which makes the basal-adjustment algorithm more conservative) and a sleep setting (which makes the basal-adjustment algorithm slightly more aggressive but turns off automated correction boluses).

In pre-market clinical trials, Control IQ achieved glucose management outcomes similar to those of Medtronic in terms of average (mid-100s) and time-in-range (above 70%) with a low frequency of hypoglycemia.  However, Tandem’s studies had few restrictions in terms of participation.  Our experience (with patients who are well-educated on diabetes self-management) has been that Control IQ produces even better outcomes.  Compared to Medtronic, the amount of work required by the user to maintain the system is much, much less.  Compared to DIY systems, the setup is much, much easier.

The Tandem pump (along with CGM data) has its own download software (t:connect) which displays sensor and pump data on the same reports, but is a bit clunky to navigate.  The reports are clear and simple, but little is offered in the way of computer-generated analysis/insight.  The pump can also be downloaded to “midware” programs such as Glooko and Tidepool.

  • Unique Advantages: Pros

    • The Pump

      The pump is sleek and easy to program, with a display that really pops.  The menus are intuitive to navigate.  The confirmation steps can be a momentary annoyance, but they greatly enhance the system’s safety.

    • The Sensor

      They say you’re only as good as the people around you.  Tandem was very, very smaht in linking with the Dexcom G6.  It’s an easy, accurate, dependable sensor that does not require fingerstick calibrations.

    • SimplicityAs noted above, Tandem built their HCL system largely around the needs of the typical consumer.  Most people do not want to have to do extra work.  And with this system, they don’t.  Just turn it on and it runs quietly and consistently in the background.  There are no added alarms or user interventions required to keep the system running other than having a steady stream of input from the CGM.
    • Updatable FeaturesOne of the unique aspects of the Tandem pump & algorithm is its flexible nature.  The software can be updated through a simple download.  The upgradeable software also means that users don’t have to wait until their pump is out of warranty to benefit from new and improved features.
    • Automatic Glucose EntriesDelivering timely, accurate bolus doses is still the responsibility of the user.  The Tandem system makes this faster, easier and more dependable by automatically populating the sensor glucose value in the blood sugar entry field whenever boluses are being calculated.  One less step and one less chance to accidentally make an incorrect entry.
    • CustomizationWhen Control IQ is running, all of the user’s usual basal and bolus settings are applied (except for the target and duration of insulin action – see cons below).  The basal part is very important, because having the proper basal settings means that the system spends less time “chasing” rising/falling blood sugars, and can focus on maintaining within a healthy range.
    • Correction BolusesThis is unique to the Control IQ algorithm.  By administering correction boluses on the user’s behalf when glucose levels are predicted to be (or already are) above 180 mg/dl, the Control IQ algorithm is faster than other HCL systems at fixing high blood sugars.  Users still have the option of programming correction boluses on their own – something that is not available in all HCL systems.tandem Sleep Mode
    • Sleep ModeWhoever thought of this deserves a nice nap.  For those who want to keep their blood sugar in a tighter/narrower range, sleep mode works quite nicely.  Some users even choose to apply sleep mode around the clock.tandem Sleep Mode
    • CoverageUnlike Medtronic’s 670G and the DIY systems, Tandem’s Control IQ is covered by Medicare and most private health insurance plans.  United Healthcare is a glaring exception (United only covers Medtronic), but that may change as pressure mounts for United to update its policy terms.

  • Potential Drawbacks: CONS

    • Lack of Training

      Don’t misunderstand.  Anyone who is new to using a Tandem pump will receive thorough training by a qualified company representative or certified private trainer.  But for those who are updating from an earlier version of a Tandem pump, face-to-face training is replaced by an online tutorial.  While this works for most people, it is not ideal for everyone.

    • Fixed IOBFor a system that offers flexibility/customization in so many ways, it is surprising that the “duration of insulin action,” which is used to calculate insulin-on-board (IOB), is not something that the user can set.  It is fixed at 5 hours, which is longer than most people’s rapid insulin lasts.  The result is a slight over-estimate of IOB most of the time.
    • Extended Bolus LimitsWhen Control IQ is running, extended bolus can be set – but only for a maximum of two hours.  While this works well for most situations, it may not be long enough for those with gastroparesis or when consuming very large/high-fat meals.
    • Limited Display InformationThe Tandem display only shows when Control IQ is currently raising/lowering basal insulin or administering a correction bolus.  Specifics are not available on the main display, nor is recent history of food, boluses, or automated adjustments (other than suspensions).
    • The ClipI realize that this has nothing to do with the hybrid closed loop aspects of the system.  But they really screwed this up.  The clip is weak, the case is awkward, and the orientation is upside down.
    • Exercise ModeAs is the case with other HCL systems, the exercise mode provides “too little too late” for preventing lows with most forms of exercise.  If set 1-2 hours prior to planned activity, it can be helpful for reducing carb requirements during a prolonged bout of exercise, but don’t develop a false sense of security.  For most traditional forms of exercise, the usual user-initiated adjustments (involving food and/or bolus insulin) are still required.
    • TubingSay what you will about tubing. Most users of traditional pumps get used to it fairly quickly.  But many still find it inconvenient and unsightly.  The change-out procedure has many steps, and air pockets sometimes form.  The need to connect/disconnect on a regular basis can also impact glucose control.

Overall, Tandem’s system offers a nice value proposition for users.  It is accessible, easy to set up and use, and produces nice results without adding any extra work/burden for the vast majority of users.

For a side-by-side comparison of all available HCL systems (including a cool star-rating for various features), visit the resources section of our website:  https://integrateddiabetes.com/what-is-a-hybrid-closed-loop-system/hybrid-closed-loop-comparisons-options/