|
|
Rachel Derr, M.D.
08-25-2010
- IFG and IGT are intermediate states of abnormal glucose homeostasis between normal and overt diabetes.
- Prediabetes is an unofficial designation including either IFG, IGT or both.
- Documentation of IFG requires only a fasting plasma glucose. Documentation of IGT requires a 75 gm oral glucose tolerance test.
- A hemoglobin A1c of 5.7 - 6.4% identifies individuals in "categories of high risk for diabetes" to whom the term pre-diabetes may be applied (ADA Standards of Medical Care in Diabetes).
- See Table 1 for exact definitions
- In the USA, prevalence of IFG = 26% and IGT = 15%, and is expected to increase (Nathan).
- 10 year incidence of IFG = 43% and IGT = 43%, in subjects with an average age of 57 years at baseline (Meigs).
- Presence of either or both abnormalities confers high risk for developing type 2 diabetes (approximately 25% in 3-5 years and up to 70% over lifetime) and modestly increased risk of cardiovascular disease (HR 1.1-1.4) (Nathan).
- Risk factors same as for diabetes (see Genetic risk factors for type 2 diabetes and Environmental risk factors for type 2 diabetes)
- Screen individuals >45 years of age or in adults of any age with BMI > 25 mg/kg2 and additional diabetes risk factors (see Genetic risk factors for type 2 diabetes and Environmental risk factors for type 2 diabetes) to identify risk for future diabetes (ADA Standards of Medical Care in Diabetes)
- Usually no overt symptoms
- Fasting plasma glucose after a minimum 8-hour fast and adequate carbohydrate intake in preceding days
- 75 gram 2 hour oral glucose tolerance test (OGTT): the gold-standard method for diagnosis of pre-diabetes, but can be time-consuming
- A1c: new criterion for "categories of increased risk for diabetes" includes HbA1c 5.7 - 6.4%
- For all these tests, risk is continuous, increasing at higher ends of the range.
- Moderate intensity exercise (30 minutes daily), weight loss (5-10% of body weight) according to the Diabetes Prevention Program (DPP) protocol, and smoking cessation
-
Metformin, to be considered for individuals with both IFG and IGT and any of the following: age <60 yo, BMI >35 mg/m2, family history of DM, high triglycerides, reduced HDL, hypertension, A1c > 6.0%.
- Other medications studied (thiazolidinediones, acarbose) may also be effective for preventing DM, but not recommended secondary to cost/adverse effects.
- DPP (3,234 patients): progression from IFG or IGT to DM over 3 years occurred in 29% of the control group vs. 14% of the intensive lifestyle group (58% reduction), and 22% of the metformin group (31% reduction); metformin was most effective in younger patients with BMI >35 (Knowler).
- Finnish Diabetes Prevention Study (522 patients): progression from IGT to DM over 4 years occurred in 23% of the control group vs. only 11% of the weight-reduction/exercise group (58% reduction) (Tuomilehto).
- At least annual follow-up for weight loss counseling and measurement of fasting glucose and serum lipids
- If on metformin, twice yearly follow-up with A1c measurement
- Patients with prediabetes do not appear to be at increased risk for retinopathy or nephropathy, but risk is higher for neuropathy and macrovascular complications, so consider screening for these.
- Diagnosing prediabetes early allows patients the opportunity to make changes to prevent or delay the onset of type 2 diabetes.
- Randomized trials show that successful lifestyle changes and moderate weight loss are more effective than any medication for preventing DM. Several pharmacologic therapies, notably metformin, are also effective.
- Lifestyle interventions are hard to implement, and weight reduction is difficult to maintain. Therefore, consider metformin if adequate weight loss is not observed after 6 months.
- Isolated impaired fasting glucose (IFG) indicates predominantly hepatic insulin resistance; isolated impaired glucose tolerance (IGT) indicates predominantly muscle insulin resistance.
- American Diabetes Association;
Standards of medical care in diabetes--2010.;
Diabetes Care;
2010; Vol.
33 Suppl 1; pp.
S11-61;
ISSN:
1935-5548;
PUBMED: 20042772
Rating:
Basis for recommendation
Comments:Screening, diagnosing, and management recommendations for favorably affecting health outcomes of patients with diabetes.
- International Expert Committee;
International Expert Committee report on the role of the A1C assay in the diagnosis of diabetes.;
Diabetes Care;
2009; Vol.
32; pp.
1327-34;
ISSN:
1935-5548;
PUBMED: 19502545
Rating:
Basis for recommendation
Comments:Consensus view from the 2008 committee that proposes the use of the A1c assay for the diagnosis of prediabetes and diabetes, suggests appropriate cut-points, and argues that A1c testing has many advantages over plasma glucose testing.
- Nathan DM, Davidson MB, DeFronzo RA, et al.;
Impaired fasting glucose and impaired glucose tolerance: implications for care.;
Diabetes Care;
2007; Vol.
30; pp.
753-9;
ISSN:
1935-5548;
PUBMED: 17327355
Rating:
Basis for recommendation
Comments:Summary of the ADA consensus position on pre-diabetic states in 2006, addressing the definition, pathogenesis, natural history, consequences, and treatment of IFG and IGT.
- Knowler WC, Barrett-Connor E, Fowler SE, et al.;
Reduction in the incidence of type 2 diabetes with lifestyle intervention or metformin.;
N Engl J Med;
2002; Vol.
346; pp.
393-403;
ISSN:
1533-4406;
PUBMED: 11832527
Rating:
Basis for recommendation
Comments:Landmark RCT showing the beneficial effects of lifestyle changes and metformin on prevention of type 2 diabetes among subjects with baseline IFG and IGT.
|
|
