SELF-MONITORING OF BLOOD GLUCOSE (SMBG)
- In type 1 diabetes A1c and number of SMBG are correlated. In children and teenagers, -0.2% for every daily test.
- Patients in intensive insulin regimes should use SMBG:
- Before meals and snacks
- At bedtime
- Before exercise
- When hypos are suspected
- After hypos until normal range is achieved
- Before and during critical activities like driving
- In patients in less intensive insulin regimes, SMBG as part of DSMES programs help guiding treatment and self-management.
- In patients not taken insulin SMBG has not proven A1c reductions, it may (level evidence E) help when changing diet, physical activity or drugs to evaluate response.
- Proper technique, validated devices and strips, and knowledge about interfering factors like high vitamin C levels or hypoxemia are neccesary to use SMBG:
- Glucose oxidase methods give falsely low levels in high oxygen tensions, like O2-therapy, and falsely high in low OT, like hypoxia or venous blood.
- Glucose oxidase methods show interference with frequently used substances like acetaminophen or ascorbic acid.
CONTINUOUS GLUCOSE MONITORING (CGM) DEVICES
Apart for blinded or professional-used devices, there are two types ot technologies: real-time (they both measure glucose and deliver data to device continuously) and intermitently scanned CGM (they measure glucose continuously but deliver data only when put in contact to a device). They can be used without calibration with SMBG.
- High level of DSMES (including SMBG technique) is neccessary for the patient to profit from this techlology.
- In adults with type 1 diabetes, both real-time and intermitent CGM are useful to reduce A1c and hypo rates, particularly in patients with A1c>target, hypoglycemia unawareness (HU) or frequent hypos, although there ar more studies for real-time devices. A1c reductions are about 0,5%, and new intermitent devices with alarms are not mentioned in this section.
- In type 2 diabetes on insulin with A1c>target, real-time CGM is useful to lower A1c and hypoglycemia. In T2DM on oral agents, whether or not with insulin, hypoglucemia does not improve. Intermitent devices showed contradictory results in T2DM.
- Consider CGM in children and adolescents with T1DM to improve glucose control, althoug benefits correlate with adherence. In this age group evidence is poorer. A1c may improve only when device is used at least 6 days per week, data on hypoglycemia are scant, and in intermitent CGM there are only observational studies.
- Real-time CGM should be used as close to daily as possible, and intermitent CGM should be scanned at least every 8 hours.
- In pregnant women with T1DM, real-time CGM is useful to improve A1c, TIR and neonatal outcomes.
- Side effects of CGM devices are contact dermatitis, sometimes associated to isobornyl acrylate, a skin sensitizer.
