The DCCT demonstrated the benefits of intensive glycemic control on diabetes complications with SMBG as part of a multifactorial intervention, suggesting that SMBG is a crucial component of effective therapy. SMBG allows patients to evaluate their individual response to therapy and assess whether glycemic targets are being achieved. SMBG results are useful in preventing hypoglycemia, adjusting medications (particularly prandial insulin doses), and understanding the impact of appropriate nutrition therapy and physical activity. More frequent SMBG is correlated to lower A1C levels.[55,56]
SMBG frequency and timing should be dictated by the patient's specific needs and goals. When prescribing SMBG, providers must ensure that patients receive ongoing instruction and regular evaluation of their SMBG technique and their ability to use SMBG data to adjust therapy (insulin and/or food). Furthermore, SMBG results should be downloaded and reviewed at each visit.
SMBG is especially important for patients with type 1 diabetes to monitor for and prevent asymptomatic hypoglycemia and hyperglycemia. Type 1 diabetic patients should perform SMBG prior to, and sometimes after, meals and snacks, at bedtime, before and after exercise, when they suspect low blood glucose, after treating low blood glucose until they are normoglycemic, and prior to critical tasks such as driving. For many patients, this will require testing 6–10 times daily, although individual needs may vary. For example, sick children may require up to 10 SMBG tests per day or more.
A study of children and adolescents with type 1 diabetes showed that, after adjustment for multiple confounders, increased SMBG frequency was significantly associated with lower A1C. In the range of 0–5 tests per day, A1C decreased by 0.46% per additional test per day. Increased testing was associated with significantly less DKA and (probably due to reverse causality) significantly more hypoglycemia.[55,56]
SMBG accuracy is dependent on both the instrument and the user, so it is important to evaluate each patient's monitoring technique, both initially and at regular intervals thereafter. Optimal use of SMBG requires a proper review and interpretation of the data by both the patient and the provider.
Real-time CGM through the measurement of interstitial glucose (which correlates well with plasma glucose) is available. These sensors require calibration with SMBG, and CGM users still require SMBG for making acute treatment decisions. CGM devices have alarms for hypo- and hyperglycemic excursions that include absolute level and rate-of-change alerts. A 26-week randomized trial of 322 type 1 diabetic patients showed that adults aged ≥25 years using intensive insulin therapy and CGM experienced a 0.5% reduction in A1C (from ~7.6% to 7.1%) compared with usual intensive insulin therapy with SMBG. Participants aged <25 years (children, teenagers, and young adults) randomized to sensor use did not achieve a significant A1C reduction. However, these younger patients did not use CGM consistently. The greatest predictor of A1C lowering for all age-groups was frequency of sensor use, which was lowest in 15- to 24-year-old subjects. There was no significant difference in hypoglycemia in any age-group. In a smaller randomized controlled trial of 129 adults and children with baseline A1C <7.0%, outcomes combining A1C and hypoglycemia favored the group using CGM, suggesting that CGM is beneficial for pediatric patients and adults with type 1 diabetes who have already achieved excellent control.
Overall, meta-analyses suggest that, compared with SMBG, CGM use is associated with A1C lowering by ~0.26% without an increase in hypoglycemia, although existing studies have small sample sizes and are of relatively short duration. The technology may be particularly useful in those with hypoglycemia unawareness and/or frequent hypoglycemic episodes, although studies have not consistently shown significant reductions in the occurrence of severe hypoglycemia. A CGM device equipped with an automatic low threshold suspend feature was approved by the U.S. Food and Drug Administration (FDA) in 2013. The Automation to Simulate Pancreatic Insulin Response (ASPIRE) trial of 247 patients showed that sensor-augmented insulin pump therapy with a low glucose suspend feature significantly reduced nocturnal hypoglycemia without increasing A1C levels for those >16 years of age. These devices may offer the opportunity to reduce severe hypoglycemia for those with a history of nocturnal hypoglycemia, although more clinical trials are needed.
Patients with type 1 diabetes should perform SMBG prior to meals and snacks, at a minimum, and at other times, including postprandially to assess insulin-to-carbohydrate ratios; at bedtime; midsleep; prior to, during, and/or after exercise; when they suspect low blood glucose; after treating low blood glucose until they have restored normoglycemia; when correcting a high blood glucose level; prior to critical tasks such as driving; and at more frequent intervals during illness or stress. (B)
Individuals with type 1 diabetes need to have unimpeded access to glucose test strips for blood glucose testing. Regardless of age, individuals may require 10 or more strips daily to monitor for hypoglycemia, assess insulin needs prior to eating, and determine if their blood glucose level is safe enough for overnight sleeping. (B)
CGM is a useful tool to reduce A1C levels in adults without increasing hypoglycemia and can reduce glycemic excursions in children. Glycemic improvements are correlated with frequency of CGM use across all ages. (A)
Additional Considerations for Pediatrics
Children should have additional blood glucose checks if the parent/caregiver is concerned that the child's behavior may be due to low/high blood glucose levels. (E)
School employees and caregivers should be knowledgeable about SMBG and equipped with all necessary supplies. (E)
Capable children should be permitted to self-manage their diabetes at school. (E)
Diabetes Care. 2014;37(7):2034-2054. © 2014 American Diabetes Association, Inc.