DM Full Guideline (2010) - VA/DoD Clinical Practice Guidelines Home

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7. A combination of pre-and postprandial tests may be performed, up to 4 times per day. [C]
VA/DoD Clinical Practice Guideline
for the Management of Diabetes Mellitus
8. The schedule of SMBG in patients on oral agents (not taking insulin) should be individualized, and
continuation justified based upon individual clinical outcomes. Consider more frequent SMBG for the
following indications:
DISCUSSION
• Initiation of therapy and/or active adjustment of oral agents
• Acute or ongoing illness
• Detection and prevention of hypoglycemia when symptoms are suggestive of such, or if there is
documented hypoglycemia unawareness
• Detection of hyperglycemia when fasting and/or post-prandial blood glucose (PPG) levels are
not consistent with HbA 1 c.
Assessment of glycemic control requires an understanding of the assessment methods, as well as their accuracy.
The HbA 1 c reflects average blood glucose over a period of time. The relationship between HbA 1 c and mean plasma
glucose is now based upon the HbA 1 c Derived Average Glucose (ADAG, 2008) study. This demonstrated a linear
relationship between HbA 1 c and mean plasma glucose (MPG) measures in patients with stable type 1 and type 2
diabetes; for an HbA 1 c of 7% the mean MPG was 154 mg/dl, with a 95% confidence interval of 123 mg/dl-185
mg/dl.
Subsequently, Herman et al., (2009) reported that although the estimated MPG (~200 mg/dl) at the time of entry into
a study of insulin analogs did not differ between Caucasian and non-Caucasian groups, HbA1c was up to 0.8%
higher in minority patients.
The measurement of HbA 1 c is subject to inter-laboratory variability, red cell survival, and the composition of red
cell hemoglobin.
(See Appendix G-1, Measurements of Glycemic Control)
Assessment of Postprandial Plasma Glucose
Glycemia can be assessed through the measurement of postprandial blood glucose (PPG), normal fasting plasma
glucose level (FPG), and HbA 1 c. The HbA 1 c level best correlates with the severity of hyperglycemia over time.
However, HbA 1 c is an integrated value. Some patients have normal fasting glucose levels and high HbA 1 c; others
have normal HbA 1 c but high fasting blood glucose levels. Troubleshooting poor glycemic control requires more
than a measurement of HbA 1 c.
There are insufficient data to accurately determine the relative contribution of the FPG and PPG to HbA 1 c. It
appears that FPG is somewhat better than PPG in predicting the level of HbA 1 c, especially in patients with type 2
diabetes. The only setting in which PPG monitoring has been shown to improve outcomes is gestational diabetes.
Regardless of whether the FPG or PPG level is determined, it is not the collection of the data, but rather the use of
the data to make clinical decisions, that lead to improvements in diabetes control. Dose adjustment of short-acting
insulin may be impractical without the measurement of PPG.
Elevated glucose values post challenge of 2-h oral glucose tolerance test [OGTT] have been associated in some
epidemiological studies with increased cardiovascular risk, independent of fasting plasma glucose. PPG levels >140
mg/dL are unusual in nondiabetic individuals, though large evening meals can be followed by plasma glucose values
up to 180 mg/dL. Pharmacological agents are available that primarily modify PPG and thereby reduce HbA 1 c in
parallel. Therefore, in individuals who have pre-meal glucose values within targets, but who are not meeting HbA 1 c
targets, consider monitoring PPG 1 to 2 hours after the start of the meal and treating to reduce average PPG values