FAQs

Glucose Implant FAQs

• How accurate is the HD-XG implant?

  The accuracy of the implant is determined by the accuracy of the calibration reference, the range used for calibration, and changes in the sensor output over time. The uncalibrated sensor output is linear to within ±5% over a range of 50-750mg/dL (2.8-41.7mmol/L). By using the best practices identified in the technical note for in vivo calibration one should be able to calibrate the sensors to within 10-15% error.

• How do I get the most accurate calibration?

  DSI provides a separate technical note with in vivo calibration instructions. Due to the importance of accurate calibration, it is recommended that all users read and understand this document.

• Why do I need to calibrate the HD-XG glucose implant in vivo?

  The HD-XG glucose sensor output is dependent on the sensor environment and is sensitive to the presence of fibrin and tissue. The sensor output observed during bench testing is not identical to the output observed when the sensor is in the blood, even when equal concentrations of glucose are present. To account for this, each sensor requires reference calibration values to be collected once the sensor has been implanted and has had at least 24 hours to stabilize in the blood. We recommend allowing the sensor to stabilize for three to four days, at the same time as surgical recovery is taking place.

• What are my options for collecting calibration reference samples?

  There are several options available for collecting accurate calibration data.
  

  • Nova StatStrip® Xpress meter and test strips require small blood samples (1.2uL) and provide immediate results (7 seconds). The StatStrip Xpress provides measurement and correction for hematocrit and other common interferents. It offers a higher level of accuracy than alternative meters and is comparable to laboratory analyticsi.
  • The “gold standard” reference is commonly thought to be a glucose analyzer from Yellow Springs Instruments such as the YSI 2300. Unlike the StatStrip Xpress, it requires a much larger blood sample (at least 25uL), it takes several minutes to obtain results, and the preferred measurement involves plasma, which requires a centrifuge and other handling logistics.
  • Similar accuracy can be obtained from reagents and diagnostic equipment from Beckman Coulter, GE, and others. Most of these methods require relatively large blood samples and there is a delay in availability of the results.

• Why is the HD-XG only warranted for 28 days of monitoring? Can I extend this duration by turning the implant off with a magnet?

  The HD-XG is warranted for 28 days from the time of implantation as that is the how long all sensors are guaranteed to function.  In practical use with the implant always turned on many glucose sensors will function for 6 to 8 weeks and some will function out to 12 weeks.
  
  Turning the implant off will not extend the life of the implant – and may even decrease the sensor's useful life.  As such, DSI recommends that the implant be turned on and left on from the time of implantation.

• How fast does the sensor respond to glucose changes?

  The glucose sensor tracks glucose changes in real time during glucose homeostasis and oral or intraperitoneal challenges.  During an intravenous bolus injection, or any large and immediate change in glucose levels, the glucose sensor may underestimate the change in glucose for approximately 1 to 2 minutes.
  
  

• Why do you have specific mouse and rat versions of the HD-XG?

  The HD-XG is available in a variety of configurations to support the unique surgical approaches for each species. 

• Are there surgical options for sensor placement besides those you recommend?

  The HD-XG sensor needs to be placed in free flowing blood just like our pressure catheters.  Our recommendations are the only options extensively tested for both sensor performance and low post-operative complication rates.  Alternatives may be feasible but we cannot guarantee their success.  Additionally, it should be noted that just because you are able to use a blood pressure catheter in an alternative location it does not mean that this glucose sensor will work post-operatively in the same manner.

• When using the HD-XG, how do I decide whether to place the transmitter body subcutaneously or intraperitoneally?

  Customer that opt for the intraperitoneal placement typically do so because they are already in that space or because a more accurate core body temperature is desired.  Subcutaneous placement is typically used when the customer prefers to not open up the peritoneum.  In rare instances the intraperitoneal placement is used as an alternative to subcutaneous placement when skin irritation has been shown to be an issue.

• Does the HD-XG work with my current telemetry system software and hardware?

  The HD-XG is supported in both Dataquest A.R.T. and Ponemah software platforms.  Versions 4.36 and 6.11 or newer are required respectively. Current telemetry hardware such as the Data Exchange Matrix or MX2 and the RPC-1 or RSC-1 receivers are also required.

• What about use in other animal models such as pigs and non-human primates?

  The HD-XG has been shown to work in swine and non-human primate models using DSI's repeater technology to overcome its short transmission range.  If this is of interest please contact your DSI sales representative or request more information.

• Does DSI plan to develop a blood glucose sensor for human use?

  No. DSI is focused on producing and developing products for preclinical life science research.

• In what research areas will continuous glucose provide value?

  We believe that Continuous Glucose Telemetry will provide significant value in a variety of research areas including but not limited to:

  • Diabetes
  • Obesity
  • Metabolism
  • Circadian Rhythms
  • Energy Expenditure
  • Ingestive Behavior
  • Stress
  • Nutrition
  • Endocrinology
  • Exercise Physiology
  • Oncology
  • Radiation
  • Trauma / PTSD
  • Degenerative CNS
  • CNS
  • Pain
  • Addiction
  • Behavior
  • Nephrology
  • Toxicology