Diagnosing And Managing Diabetes – Classification and Diagnosis
A. Classification
In 1997, the ADA issued new diagnostic and classification criteria; in 2003, modifications were made regarding the diagnosis of impaired fasting glucose (IFG). The classification of diabetes includes four clinical classes:
* Type 1 diabetes (results from ??-cell destruction, usually leading to absolute insulin deficiency).
* Type 2 diabetes (results from a progressive insulin secretory defect on the background of insulin resistance).
* Other specific types of diabetes due to other causes, e.g., genetic defects in ??-cell function, genetic defects in insulin action, diseases of the exocrine pancreas (such as cystic fibrosis), and drug or chemical induced (such as in the treatment of AIDS or after organ transplantation).
* Gestational diabetes mellitus (GDM) (diagnosed during pregnancy).
B. Diagnosis
Recommendations
* The FPG is the preferred test to diagnose diabetes in children and nonpregnant adults. (E)
* The use of the A1C for the diagnosis of diabetes is not recommended at this time. (E)
Criteria for the diagnosis of diabetes in nonpregnant adults are shown in Table 2. Three ways to diagnose diabetes are available, and each must be confirmed on a subsequent day unless unequivocal symptoms of hyperglycemia are present. Although the 75-g oral glucose tolerance test (OGTT) is more sensitive and modestly more specific than fasting plasma glucose (FPG) to diagnose diabetes, it is poorly reproducible and rarely performed in practice. Because of ease of use, acceptability to patients, and lower cost, the FPG is the preferred diagnostic test. It should be noted that the vast majority of people who meet diagnostic criteria for diabetes by OGTT, but not by FPG, will have an A1C value <7.0%. The use of the A1C for the diagnosis of diabetes is not recommended at this time.
Table 2??a glucose 200 mg/dl (11.1 mmol/l) during an OGTT. The test should be performed as described by the World Health Organization, using a glucose load containing the equivalent of 75-g anhydrous glucose dissolved in water.
Hyperglycemia not sufficient to meet the diagnostic criteria for diabetes is categorized as either IFG or impaired glucose tolerance (IGT), depending on whether it is identified through a FPG or an OGTT:
* IFG = FPG 100 mg/dl (5.6 mmol/l) to 125 mg/dl (6.9 mmol/l)
* IGT = 2-h plasma glucose 140 mg/dl (7.8 mmol/l) to 199 mg/dl (11.0 mmol/l)
Recently, IFG and IGT have been officially termed “pre-diabetes.” Both categories, IFG and IGT, are risk factors for future diabetes and cardiovascular disease (CVD).
In the absence of unequivocal hyperglycemia, these criteria should be confirmed by repeat testing on a different day. The OGTT is not recommended for routine clinical use but may be required in the evaluation of patients with IFG (see text) or when diabetes is still suspected despite a normal FPG, as with the postpartum evaluation of women with GDM.
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AMERICAN DIABETES ASSOCIATION
DIABETES CARE, VOLUME 27, SUPPLEMENT 1, JANUARY 2004
References
1. Bode BW (Ed.): Medical Management of Type 1 Diabetes. 4th ed. Alexandria, VA, American Diabetes Association, 2004
2. Zimmerman BR (Ed.): Medical Management of Type 2 Diabetes. 4th ed. Alexandria, VA, American Diabetes Association, 1998
3. Kilingensmith G (Ed.): Intensive Diabetes Management. 3rd ed. Alexandria, VA, American Diabetes Association, 2003
4. The Expert Committee on the Diagnosis and Classification of Diabetes Mellitus: Report of the Expert Committee on the Diagnosis and Classification of Diabetes Mellitus. Diabetes Care 20:1183-1197, 1997
4a.World Health Organization: Diabetes Mellitus: Report of a WHO Study Group. Geneva, World Health Org., 1985 (Tech. Rep. Ser., no. 727)
5. The Expert Committee on the Diagnosis and Classification of Diabetes Mellitus: Follow-up report on the diagnosis of diabetes mellitus. Diabetes Care 26:3160 – 3167, 2003
6. Tuomilehto J, Lindstrom J, Eriksson JG, Valle TT, Hamalainen H, Ilanne-Parikka P, Keinanen-Kiukaaniemi S, Laakso M, Louheranta A, Rastas M, Salminen V, Uusitupa M: Prevention of type 2 diabetes mellitus by changes in lifestyle among subjects with impaired glucose tolerance. N Engl J Med 344:1343-1350, 2001
7. Pan XR, Li GW, Hu YH, Wang JX, Yang WY, An ZX, Hu ZX, Lin J, Xiao JZ, Cao HB, Liu PA, Jiang XG, Jiang YY, Wang JP, Zheng H, Zhang H, Bennett PH, Howard BV: Effects of diet and exercise in preventing NIDDM in people with impaired glucose tolerance: the DaQing IGT and Diabetes Study. Diabetes Care 20:537- 544, 1997
8. The Diabetes Prevention Program Research Group: Reduction in the incidence of type 2 diabetes with lifestyle intervention or metformin. N Engl J Med 346:393- 403, 2002
9. Chiasson JL, Josse RG, Gomis R, Hanefeld M, Karasik A, Laakso M: Acarbose for prevention of type 2 diabetes mellitus: the STOP-NIDDM randomized trial. Lancet 359:2072-2077, 2002
10. Sjostrom L, et al: XENDOS (Xenical in the prevention of diabetes in obese subjects): a landmark study. Poster presented at the International Congress on Obesity (ICO), San Paulo, Brazil, 2002
11. Buchanan TA, Xiang AH, Peters RK, Kjos SL, Marroquin A, Goico J, Ochoa C, Tan S, Berkowitz, Hodis HN, Azen SP: Preservation of pancreatic β-cell function and prevention of type 2 diabetes by pharmacological trewatment of insulin resistance in high-risk hispanic women. Diabetes 51:2796 -2803, 2002
12. Engelgau ME, Narayan KMV, Herman WH: Screening for type 2 diabetes (Technical Review). Diabetes Care 23:1563-1580, 2000 [erratum appears in Diabetes Care 23:1868 -1869, 2000]
13. American Diabetes Association: Type 2 diabetes in children and adolescents (Consensus Statement). Diabetes Care 23:381-389, 2000
14. American Diabetes Association: Gestational diabetes mellitus (Position Statement). Diabetes Care 27 (Suppl. 1):S88 – S90, 2004
15. The Diabetes Control and Complications Trial Research Group: The effect of intensive treatment of diabetes on the development and progression of longterm complications in insulin-dependent diabetes mellitus. N Engl J Med 329: 977-986, 1993
16. The UK Prospective Diabetes Study Group: Intensive blood-glucose control with sulphonylureas or insulin compared with conventional treatment and risk of complications in patients with type 2 diabetes (UKPDS 33). Lancet 352: 837- 853, 1998
17. The UK Prospective Diabetes Study Group: Effect of intensive blood-glucose control with metformin on complications in overweight patients with type 2 diabetes (UKPDS 34). Lancet 352:854 -865, 1998