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Chico et al. (2003) conducted a randomized controlled trial in 75 adults with inadequately controlled type 1 diabetes to evaluate MiniMed CGMS as an adjunct to SMBG for improvement of glycemic control. Patients assigned to CGM underwent three days of CGM and were then monitored for three months to assess the results of therapy modifications.
The results suggested that CGM does not improve glycemic control in adult patients with type 1 diabetes.
Another small prospective controlled trial compared glucose levels in type 1 diabetics (n=10) and normal controls (n=10) with use of the MiniMed CGMS (72 hours). A total of 41% of hypoglycemic events that were identified by the patient were not recognized by CGMS. In addition, CGMS may have overreported hypoglycemic events that may not be actual hypoglycemia. The investigators concluded that adjustment of insulin doses to reduce asymptomatic hypoglycemia identified by the CGMS alone may not be warranted (Larsen et al., 2004).
A large randomized controlled study (n=128) found that patients in both CGMS and SMBG groups experienced significant reductions in A1C from baseline to 12 weeks, although there were no significant differences in A1C between the two groups. Patients in the CGMS group experienced a significantly reduced duration of hypoglycemia after 12 weeks compared with patients monitored with SMBG (Tanenberg et al., 2004).
Sachedina and Pickup (2003) found that CGMS detected significantly greater number of hypoglycemia and postprandial hyperglycemia events than SMBG, although a relatively high percentage (28%) of sensors were not functioning after insertion and required replacement.
The results of the Minimally Invasive Technology Role and Evaluation (MITRE) study were presented at the 2007 ADA 67th Scientific Sessions (Newman et al., 2007). This RCT compared the efficacy of two CGM devices in adult patients with insulin-dependent diabetes. The primary endpoint was long-term glucose control, as indicated by changes in A1C Continuous Glucose Monitoring and Insulin Pumps for Managing Diabetes - Commercial Medical Management Guideline levels at 18 months. The patients were randomized to the MiniMed CGMS (n=102), the Biographer (n=100), standard control (n=102) or attention control (n=100). By month 18, the percentage of patients who had a relative reduction of A1C of at least 12.5% was 15% in the Biographer group, 27% in the CGMS group, 24% in the standard control, and 27% in the attention control group. The investigators found that CGMS has a small benefit but it does not last and the Biographer had a smaller effect on A1C than the MiniMed CGMS or standard treatments.
Next Generation Real-time Continuous Glucose Monitoring Systems: The literature search identified six studies in adult diabetics using CGMS that provided access to real-time data. Three short-term studies evaluated whether unblinded access to real-time continuous glucose data and alerts/alarms improved management of hypoglycemic and hyperglycemic events. (Garg et al., 2006a; Garg and Jovanovic et al. 2006b; Bode et al., 2004) The other three studies, including one RCT (Deiss et al., 2006b), one nonrandomized controlled study (Garg et al., 2007) and one uncontrolled study (Bailey et al., 2007), were 12-week studies evaluating the effect of real-time CGM on glycemic control (A1C levels) after. One study (Deiss et al, 2006b) included adults and children. All studies had some design flaws including heterogeneous patient population, or short-term follow-up.
One randomized controlled trial (Garg et al. 2006a) evaluated the diagnostic performance and clinical effectiveness of the DexCom STS CGMS in 91 adult patients with either type 1 (n=75) or type 2 (n=16) insulin-requiring diabetes. Each subject participated in three, 72-hour cycles of monitoring. Results indicate that patients who were provided unblinded access to continuous glucose data and alerts/alarms were more effectively able to managing hypoglycemic and hyperglycemic events.
A similar study was conducted by Garg and Jovanovic (2006b) to evaluate the safety and efficacy of seven-day abdominal, transcutaneous, real-time CGM (DexCom STS) in a heterogeneous study group including type 1 (n=69) and type 2 (n=17) insulin-requiring diabetics. Study results showed that presenting real-time glucose values to patients was associated with a decrease in the time spent in the hyper- and hypoglycemic ranges while increasing the time spent in the euglycemic range. The greatest improvements were observed in patients with higher A1C baseline values.
Bode et al. (2004) evaluated the effectiveness of alarms based on real-time sensor glucose values provided by the MiniMed Guardian CGMS in 71 adult diabetics. Patient responses to the hypoglycemia alerts resulted in a significantly reduced duration of hypoglycemic events compared with controls, although overtreatment of hypoglycemia may have caused a small increase in the frequency of hyperglycemic events.
Deiss et al. (2006b) reported on a 3-month study of 81 children and 81 adults with stable type 1 diabetes who had A1C levels of 8.1% or greater. Patients were randomized to continuous real-time monitoring with the Guardian RT, continuous monitoring for 3 days every 2 weeks, or SMBG. At 3 months, 50% of patients with continuous real-time monitoring had a decrease in A1C of at least 1% compared to 37% of those with intermittent continuous monitoring, and 15% of controls.
An A1C reduction of at least 2% was seen in 26% of group 1 patients, 9% of group 2 patients and 4% of control group patients. The investigators reported that the patients did not record specific information regarding daily self-management activities but reported that changes were made. Therefore, delineation between the link between CGM and improvement in glycemic control could not be made.
In a small nonrandomized comparison study Garg et al. (2007) evaluated real-time CGM with DexCom STS (n=24). At 12 weeks a modest but significant improvement in A1C (0.4%) was observed in the CGM group compared to nonsignificant increase in A1C (0.3%) in the comparison group (n=23). Also, at 12 weeks there was a difference in A1C values between groups despite the fact that there was no change in insulin dose. The number of subjects achieving A1C values Similar results were reported by Bailey et al. (2007) who conducted an observational trial evaluating the DexCom STS in a heterogeneous patient population (n=139) including type 1 and type 2 diabetics. Overall, at the end of the 12-week study, the A1C was reduced by 0.4%. Decrease in A1C was more pronounced in patients with higher baseline levels. Patients did Continuous Glucose Monitoring and Insulin Pumps for Managing Diabetes - Commercial Medical Management Guideline not report an increase in the time spent in hypoglycemia. Patients in the top quartile of CGM attention experienced a greater A1C reduction compared to those in the bottom quartile.
In summary, the study results showed that presenting real-time glucose values to patients was associated with a decrease in the time spent in the hyper- and hypoglycemic ranges while increasing the time spent in the euglycemic range.
However, the real-time CGM had only a modest effect on glycemic control. Poorly controlled patients (high baseline A1C values) had the largest improvement. Long-term follow-up data beyond 3 months are not yet available.
Pediatric Patients The literature search identified eight RCTs that evaluated the use of the first-generation devices MiniMed CGMS or GlucoWatch G2 Biographer in children with type 1diabetes.
Chase et al. (2003) conducted a single-blinded, randomized controlled trial to evaluate the GlucoWatch Biographer as an adjunct to SMBG in 40 children. The study group was asked to wear the sensors four times per week for twelve hours for three months. Results suggested that in diabetic children, CGM improved glycemic control and detection of hypoglycemia.
In a controlled crossover trial, Ludvigsson and Hanas (2003) reported improved glycemic control in 27 pediatric patients.
All patients underwent CGM with MiniMed CGMS for three days every other week for 24 weeks as an adjunct to SMBG.
Patients were randomized to CGM data available for 12 weeks with crossover to data unavailable for 12 weeks.
Chase et al. (2001) conducted a randomized controlled study to evaluate MiniMed CGMS as an adjunct to SMBG for glycemic control in 11 children. Patients in the continuous glucose monitoring group (n=6) underwent 18 days of CGM during a 30-day period. Results suggested that, while CGM may improve detection of asymptomatic hypoglycemia, it does not improve glycemic control.
Deiss et al. (2006a) reported results of a small double-blinded, cross-over randomized trial in children with type 1 diabetes. During the first 12 weeks, group A (n=15) had access to the MiniMed CGMS data while group B (n=15) was blinded to the CGMS data. At the end of three months, the groups crossed over. The authors found that visual interpretation of CGMS data resulted in frequent changes in insulin therapy, but had no effect on metabolic control (no significant decease in A1C levels) and duration of hyperglycemia.
In a larger trial of 200 pediatric patients, the DirecNet Study Group (Chase et al., 2005) evaluated the GlucoWatch Biographer compared with SMBG and did not find statistically significant decreases in the levels of A1C or a reduction in the frequency of severe hypoglycemia in pediatric patients. In the same study group (Fiallo-Scharer et al., 2005), with the same or overlapping population, the investigators reported that mean overall glucose levels and A1C levels were similar between MiniMed CGMS and 8-point glucose testing. However, CGMS may have overreported the frequency of hypoglycemic events at night.
Yates et al. (2006) randomized 36 children with type 1 diabetes to insulin adjustment on the basis of 72 h of continuous glucose monitoring with the MiniMed CGMS every 3 weeks or intermittent SMBG for 3 months. There was a significant improvement in A1C from baseline values in both groups, but there was no difference in the degree of improvement in A1C at 12 weeks between the CGMS (n=19) and the control group (n=17). Investigators concluded that CGMS might be no more useful than SMBG for improving diabetes control in pediatric patients on intensified insulin regimens.
Lagarde et al. (2006) conducted a small (n=27) randomized trial and reported that CGMS may improve metabolic control in children with type 1 diabetes since A1C levels decreased in the treatment group compared with the control group after 6 months. This decrease, however, was small.
Continuous Glucose Monitoring and Insulin Pumps for Managing Diabetes - Commercial Medical Management Guideline Next Generation Real-time Continuous Glucose Monitoring Systems: Three studies including one RCT (Deiss et al., 2006b) were found that assessed the effectiveness of unblinded sensor access in children with type 1 diabetes.
The GuardControl study (Deiss et al., 2006b) that included poorly controlled adults (n=81) and children (n=81) despite intensive insulin therapy showed that, within three months, real-time continuous glucose monitoring with the Guardian RT led to significantly improved A1C values. The study did not report age-specific outcomes. (See also section Adult Patients) The Diabetes Research in Children Network (DirecNet) Study Group examined the feasibility of daily use of a continuous glucose monitor, the FreeStyle Navigator CGMS in children with type 1 diabetes using insulin pumps. Mean A1C improved from 7.1% at baseline to 6.8% at 13 weeks of unblinded sensor use, and the percentage of glucose values in the target range increased from 52% to 60%. There was a modest increase in the percentage of sensor values that were level fell from 7.9 at baseline to 7.3 at 13 weeks (Weinzimer et al., 2008).
Gestational Diabetes Three RCTs evaluated the use of CGM in pregnant women with either type 1 diabetes (Yogev et al., 2003), or gestational diabetes (Buhling et al., 2005; Kestila, et al., 2007) Buhling et al. (2005) reported that CGMS detected more frequent and longer periods of hyperglycemia. Compared with SMBG, CGMS also offered more differentiation between nondiabetic pregnant women, patients with gestational diabetes and patients with impaired glucose tolerance. A second small study found that when CGMS was used to adjust insulin treatment, there was a reduction in undetected hyperglycemia and nocturnal hypoglycemic events. However, the study did not indicate a clinical difference in perinatal outcomes between CGMS and SMBG (Yogev et al., 2003). Kestila, et al.
(2007) conducted a randomized controlled trial to compare CGMS (n=36) to SMBG (n=37) in detecting patients with gestational diabetes mellitus (GDM) who needed antidiabetic drug treatment. In 11 out of 36 patients (31%) monitored with CGMS antihyperglycemic drug therapy was introduced whereas only 3/37 (8%) in the SMBG group were drugtreated. The authors concluded that further large-scale studies are needed to evaluate whether CGMS guided initiation of antihyperglycemic therapy results in less macrosomia and perinatal complications related to GDM.
Insulin Pump and Continuous Glucose Monitoring Combined Systems Two uncontrolled studies and a technology assessment report were found that assessed the MiniMed Paradigm REAL Time System when used as an open-loop system (current FDA approved indication). Another technology assessment report assessed the device when used as closed-loop system.
In a small preliminary study of the Paradigm REAL Time System, Mastrototaro et al. (2006) evaluated the glucose monitoring functions of this device to guide patients in self-administration of insulin. This study enrolled 20 patients with type 1 diabetes who were employees of the device manufacturer. After a mean follow-up of 10 months, mean A1C levels had decreased from 7.4% to 6.3%.
Halvorson et al. (2007) enrolled 10 pediatric patients with type 1 diabetes into an uncontrolled study of the Paradigm REAL-Time System. Over the course of the study, mean A1C levels decreased from 8.1% to 7.8%; the time spent in hypoglycemia decreased and the time spent in hyperglycemia decreased.
The Canadian Agency of Drugs and Technologies in Health (CADTH) published a report on the Paradigm Real-Time System. (Pohar, 2007). The report concluded that based on the limited amount of published research to date, the impact of the Paradigm Real-Time System on long-term glycemic control, prevention of diabetic complications, or quality of life is unclear. The report included four studies, three of which were abstracts presented at the 2007 ADA Scientific Sessions.