Definition, Classification and Diagnosis of Diabetes, Prediabetes and Metabolic Syndrome

Canadian Diabetes Association Clinical Practice Guidelines Expert Committee

Ronald Goldenberg MD, FRCPC, FACE Zubin Punthakee MD, MSc, FRCPC

  • Key Messages
  • Recommendations
  • Figures
  • Highlights
  • Full Text
  • References

Key Messages

  • The chronic hyperglycemia of diabetes is associated with significant long-term microvascular and macrovascular complications.
  • A fasting plasma glucose level of ≥7.0 mmol/L, a 2-hour plasma glucose value in a 75 g oral glucose tolerance test of ≥11.1 mmol/L or a glycated hemoglobin (A1C) value of ≥6.5% can predict the development of retinopathy. This permits the diagnosis of diabetes to be made on the basis of each of these parameters.
  • The term “prediabetes” refers to impaired fasting glucose, impaired glucose tolerance or an A1C of 6.0% to 6.4%, each of which places individuals at high risk of developing diabetes and its complications.

Highlights of Revisions

  • The title of this chapter has been revised to specifically include "prediabetes" and "metabolic syndrome." Since 2008, more data have been published showing the growing incidence of these conditions and their relation to the prevention and diagnosis of type 1 and type 2 diabetes.
  • Diabetes can be diagnosed if glycated hemoglobin (A1C) is ≥6.5%.
  • Prediabetes can be diagnosed with an A1C of 6.0% to 6.4%.
Table 1
Diagnosis of diabetes
2hPG, 2-hour plasma glucose; A1C, glycated hemoglobin; FPG, fasting plasma glucose; OGTT, oral glucose tolerance test; PG, plasma glucose.
FPG ≥7.0 mmol/L
Fasting = no caloric intake for at least 8 hours
or
A1C ≥6.5% (in adults)
Using a standardized, validated assay in the absence of factors that affect the accuracy of the A1C and not for suspected type 1 diabetes (see text)
or
2hPG in a 75 g OGTT ≥11.1 mmol/L
or
Random PG ≥11.1 mmol/L
Random = any time of the day, without regard to the interval since the last meal

In the absence of symptomatic hyperglycemia, if a single laboratory test result is in the diabetes range, a repeat confirmatory laboratory test (FPG, A1C, 2hPG in a 75 g OGTT) must be done on another day. It is preferable that the same test be repeated (in a timely fashion) for confirmation, but a random PG in the diabetes range in an asymptomatic individual should be confirmed with an alternate test. In the case of symptomatic hyperglycemia, the diagnosis has been made and a confirmatory test is not required before treatment is initiated. In individuals in whom type 1 diabetes is likely (younger or lean or symptomatic hyperglycemia, especially with ketonuria or ketonemia), confirmatory testing should not delay initiation of treatment to avoid rapid deterioration. If results of 2 different tests are available and both are above the diagnostic cutpoints, the diagnosis of diabetes is confirmed.

Table 2
Diagnosis of prediabetes
2hPG, 2-hour plasma glucose; A1C, glycated hemoglobin; FPG, fasting plasma glucose; IFG, impaired fasting glucose; IGT, impaired glucose tolerance; OGTT, oral glucose tolerance test.
Test Result Prediabetes category
FPG (mmol/L) 6.1–6.9 IFG
2hPG in a 75 g OGTT (mmol/L) 7.8–11.0 IGT
A1C (%) 6.0–6.4 Prediabetes

Recommendations

  1. Diabetes should be diagnosed by any of the following criteria:
    • FPG ≥7.0 mmol/L [Grade B, Level 2 (1)]
    • A1C ≥6.5% (for use in adults in the absence of factors that affect the accuracy of A1C and not for use in those with suspected type 1 diabetes) [Grade B, Level 2 (1)]
    • 2hPG in a 75 g OGTT ≥11.1 mmol/L [Grade B, Level 2 (1)]
    • Random PG ≥11.1 mmol/L [Grade D, Consensus]
  2. In the absence of symptomatic hyperglycemia, if a single laboratory test result is in the diabetes range, a repeat confirmatory laboratory test (FPG, A1C, 2hPG in a 75 g OGTT) must be done on another day. It is preferable that the same test be repeated (in a timely fashion) for confirmation, but a random PG in the diabetes range in an asymptomatic individual should be confirmed with an alternate test. In the case of symptomatic hyperglycemia, the diagnosis has been made and a confirmatory test is not required before treatment is initiated. In individuals in whom type 1 diabetes is likely (younger or lean or symptomatic hyperglycemia, especially with ketonuria or ketonemia), confirmatory testing should not delay initiation of treatment to avoid rapid deterioration. If results of two different tests are available and both are above the diagnostic cutpoints, the diagnosis of diabetes is confirmed [Grade D, Consensus].
  3. Prediabetes (defined as a state which places individuals at high risk of developing diabetes and its complications) is diagnosed by any of the following criteria:
    • IFG (FPG 6.1–6.9 mmol/L) [Grade A, Level 1 (2)]
    • IGT (2hPG in a 75 g OGTT 7.8–11.0 mmol/L) [Grade A, Level 1 (2)]
    • A1C 6.0%–6.4% (for use in adults in the absence of factors that affect the accuracy of A1C and not for use in suspected type 1 diabetes) [Grade B, Level 2 (3)].

Abbreviations:
2hPG , 2-hour plasma glucose; A1C , glycated hemoglobin; FPG , fasting plasma glucose; IFG , impaired fasting glucose; IGT , impaired glucose tolerance; OGTT , oral glucose tolerance test; PG , plasma glucose.

References

  1. The DETECT-2 Collaboration Writing Group. Glycemic thresholds for diabetes specific retinopathy. Diabetes Care 2011;34:145e50.
  2. Santaguida PL, Balion C, Morrison K, et al. Diagnosis, prognosis, and treatment of impaired glucose tolerance and impaired fasting glucose. Evidence report/technology assessment no. 128. Agency Healthcare Research and Quality Publication No. 05-E026-2. Rockville, MD: Agency for Healthcare Research and Quality; September 2005.
  3. Zhang X, Gregg E, Williamson D, et al. A1C level and future risk of diabetes: a systematic review. Diabetes Care 2010;33:1665e73.

 

Reproduced with permission from Canadian Journal of Diabetes © 2013 Canadian Diabetes Association. To cite this article, please refer to For citation.