Table 1.
Continuous glucose monitoring systems. MARD, mean absolute relative difference; EGA, error grid analysis; CE, Conformité Européenne; DG4P, Dexcom G4TM PLATINUM; FN, FreeStyle Navigator®.
| CGMS (Company) | Device Characteristics |
|---|---|
| Dexcom SEVEN® Plus (Dexcom) |
Target site: skin Technology used: glucose sensor; sensor lifespan: 168 h; length of sensor probe: 13 mm; gauge of sensor probe: 26 mm; sensor warm up: 2 h; calibration every 12 h, but twice within the first 30 min. Advantages: use FDA-approved glucose sensor that can be used for up to seven days; precisely detect hypoglycemic glucose level; water-resistant transmitter with built-in battery lasting one year; transmits glucose sensing data to the handheld receiver within five feet range every 5 min; receiver shows trends and current glucose level; stores up to 30 days of glucose trends along with a record of activities and events; comes with Dexcom® Data Manager 3 software, which provides better insight into the ways to improve glycemic control. Disadvantages: invasive; is a previous generation of CGMS that is not being used anymore; requires calibration with blood glucose testing; requires a change of the sensor after a few days. Reliability: MARD in euglycemia region = 18.4%; MARD in hypoglycemia region = 22.5%; Clarke EGA in euglycemia region = 98.3% in A + B, 91.3% in A; Clarke EGA in hypoglycemia region = NA [56]. MARD in hypoglycemia region = 21.5% [57]; aggregate MARD = 16% [58]; 76% of DG4P sensors had an individual MARD of ≤20%; DG4P had a mean absolute difference of 16 mg/dL for hypoglycemia (Yellow Springs Instrument Company’s YSI blood glucose analyzer < 70 mg/dL) [58]. Cost: US $1,158 for CGMS and US $349 for four sensors. Availability: USA, UK, European Union, Asian and Latin American countries that recognize the CE mark. |
| Dexcom G4TM PLATINUM (Dexcom) |
Target site: skin Technology used: glucose sensor; sensor lifespan: 168 h; length of sensor probe: 13 mm; gauge of sensor probe: 26 mm; sensor warm up: 2 h; calibration every 12 h, but twice within the first 30 min. Advantages: compact, wearable and light-weight; measures glucose continuously every 5 min; transmit glucose readings to the receiver up to a distance of 6 m; employs a very thin glucose sensor that can be used for up to seven days and has the same diameter as a human hair; high precision; receiver with colored screen and alarm alerts for high and low glucose levels and when the glucose levels are rising or falling quickly; comes with Dexcom STUDIOTM data management software, which enables simple navigation and an illustrative visual for the quick and easy identification of glucose patterns. Disadvantages: invasive; requires calibration with blood glucose testing every 12 h; requires a change of the sensor after a few days. Reliability: aggregate MARD = 13%; 90% of DG4P sensors had an individual MARD of ≤20%; DG4P had a mean absolute difference of 11 mg/dL for hypoglycemia (YSI < 70 mg/dL) [58]. Cost: US $1,198 for CGMS and US $349 for a four-pack of sensors. Daily cost of US $6.70. Availability: USA, European Union, Asian and Latin American countries that recognize the CE mark. |
| Guardian® REAL-time (Medtronic) |
Target site: skin Technology used: glucose sensor; sensor lifespan: 72 h; length of sensor probe: 14 mm; gauge of sensor probe: 23 mm; sensor warm up: 2 h; calibration at 2 h, 8 h and then every 12 h. Advantages: measures glucose levels in the interstitial fluid every 10 s; wireless transmitter attached to a glucose sensor transmits average glucose reading to the monitor every 5 min; employs a glucose sensor that can be used for up to six days; displays glucose trends on the receiver; alarm alerts for high and low glucose levels; predictive alerts notify the user up to 30 min before they are predicted to reach a personal low or high glucose level; Disadvantages: invasive; requires calibration with blood glucose testing; requires a change of the sensor after a few days. Reliability: MARD in euglycemia region = 13.3%; MARD in hypoglycemia region = 13.8%; Clarke EGA in euglycemia region = 98.9% in A + B, 91.3% in A; Clarke EGA in hypoglycemia region = 84.4 in A + B, 81.9 in A [56]; 72% in A zone and 27.6% values in B zones of Clarke EGA; and a MARD of 17.6% [59]. Cost: US $1,400 for CGMS and US $50 for a sensor. Availability: USA, Europe, India |
| FreeStyle Navigator® (Abbott) |
Target site: skin Technology used: glucose sensor; sensor lifespan: 120 h; length of sensor probe: 6 mm; sensor warm up: 10 h; calibration at 10 h, 12 h, 24 h and 72 h. Advantages: measures glucose level every 1 min; employs a glucose sensor that can be used for CGM for up to five days; transmits glucose measurement data to the receiver up to 3 m; cellphone-sized receiver is a stand-alone unit with integrated blood glucose testing; built-in FreeStyle blood glucose meter provides convenient calibration using the test strips used in Abbott’s FreeStyle Lite blood glucose meter; receiver’s screen displays the current glucose level, glucose trend and the continuous glucose measurements; transmitter is compact, light, waterproof and battery-powered; reliable early-warning alarms alert for high and low glucose levels up to 30 min in advance. Disadvantages: invasive; requires calibration with a built-in blood glucose meter; requires a change of the sensor after a few days. Reliability: MARD in euglycemia region = 11.8%; MARD in hypoglycemia region = 7.4%; Clarke EGA in euglycemia region = 98.6% in A + B, 93.7% in A; Clarke EGA in hypoglycemia region = 97% in A + B, 95.5% in A [56]; MARD in hypoglycemia region = 29.8% [57]. 93.7%, 3.6% and 2.8% readings in the A, B and clinical error regions of EGA, respectively [60]; the clinical accuracy of the FN in the first 10 h and subsequent hours were 92.6% and 94.2%, respectively; FN has the MARD and median absolute relative difference of 12.8% and 9.3%, respectively [61]; the readings in the A and B zones of EGA were 81.7% and 6.7%, respectively. Cost: US $1,000 for the receiver and transmitter and US $375 for a pack of six sensors. Availability: USA, UK |
| FreeStyle Navigator II (Abbott) |
Target site: skin Technology used: glucose sensor; sensor lifespan: 120 h; length of sensor probe: 6 mm; sensor warm up: 10 h; calibration at 10 h, 12 h, 24 h and 72 h. Advantages: compact, lightweight and comfortable to wear in comparison to its predecessor, i.e., FreeStyle Navigator®; employs a glucose sensor that can be used for CGM for up to five days; compact transmitter with capsuled battery; compact and easy-to-use receiver with capsuled reloadable battery cell and illuminated color display; provides continuous glucose levels every minute, blood glucose averages of the last 10 min and the low and high blood glucose levels; provides greater flexibility, due to non-interference with the everyday activities of the diabetic; provides glucose trend and its direction; provides early warning alarm alerts if there is the risk of too low or too high glucose levels; works during showering, swimming, exercising or traveling and can transmit glucose sensing data to the receiver at an extended range of 30 m; can also be used for children above six years of age and adolescents under the supervision of an adult; built-in FreeStyle blood glucose meter; appropriate for evaluating the blood glucose fluctuations in the short term and additionally provides decision support in difficult treatment scenarios. Disadvantages: invasive; requires calibration with built-in blood glucose meter; requires a change of the sensor after a few days. Reliability: NA* Cost: US $1,524 for the receiver and transmitter and US $64.20 for a sensor; daily cost of US $7.50. Availability: a few European countries, South America, India |
| HG1-c (C8 Medisensors) |
Target site: skin Technology used: Raman spectroscopy Advantages: compact, wearable and light-weight; non-invasive glucose monitoring; CE-approved; small and water-resistant glucose sensor; glucose measurement every 5 min; precision comparable to blood glucose meters; transmission of CGM data continuously to a smartphone; smartphone can view 3 h of instantaneous readings and the previous four months’ readings for a retrospective view; customized personal alerts for high and low glucose levels; no requirement for constant recalibration; cost-effective compared to fingerstick tests based on estimates for four years with three fingerstick tests per day. Disadvantages: approved for investigational use in the US. Reliability: 53% in A and 92% in A + B zones of EGA [62]. Cost: US $4,000 for CGMS. Availability: NA* |
| GlucoTrack™ (Integrity Applications Ltd.) |
Target site: ear lobe skin Technology used: ultrasound, electromagnetic and heat capacity Advantages: compact and light-weight; large LCD screen; high precision due to the use of various non-invasive glucose monitoring techniques; alerts for hypo- and hyper-glycemia; multi-user support; easy calibration procedure with the calibration being valid for a month; USB and infra-red (IR) connectivity; data storage capacity; software for data analysis; readings unaffected by daily routine activities; good correlation with glucose meters and glucose analyzers; and high accuracy in clinical trials. Disadvantages: must be individually calibrated against invasive basal and post-prandial blood glucose references before use; requires tremendous improvements in the calibration procedure and algorithm for data processing. Reliability: 92% in A + B with 50% in the A zone of EGA. The MARD and median relative absolute difference were 29.9% and 19.9% [63]. Cost: US $1,926 for CGMS. Availability: NA * |
| OrSense NBM-200G (OrSense Ltd.) |
Target site: fingertip skin Technology used: occlusion near infrared spectroscopy Advantages: portable; easy-to-use; measures glucose in less than a minute; data storage capacity, alerts for hypo- and hyper-glycemia; data analysis trend; integrated wireless telemetry; allows non-invasive glucose measurement together with hemoglobin and oxygen saturation; easy calibration procedure with no requirement for frequent calibrations; CGM for 24 h; good accuracy in clinical trials; precision comparable to glucose meters; and CE approved. Disadvantages: NM ** Reliability: 95.3% in the A + B and 4.7% in C + D zones of EGA. Cost: NA* Availability: NA * |
| Symphony® (Echo Therapeutics, Inc.; previously Sontra Medical Corporation) |
Target site: skin Technology used: Prelude® SkinPrep System Advantages: compact and light-weight; measures glucose every min; integrated wireless telemetry; alarm alerts for rapid changes in glucose levels; brief warm up period; no skin irritation; highly successful clinical trials; good correlation with glucose analyzers and glucose meters. Disadvantages: NM ** Reliability: The accuracy was determined in three study groups, i.e., study I in diabetics, study II in patients undergoing cardiac surgery and study III in healthy volunteers [64]. There were 89.6%, 86.4% and 89.9% readings in zone A, and 9%, 13.6% and 10.1% readings in zone B of study I, II and III, respectively. Cost: NA * Availability: NA * |
* NA: Not Available;
** NM: Not Mentioned.