Current issues of ACP Journal Club are published in Annals of Internal Medicine


Diagnosis

A 2-hour oral glucose tolerance test result ≥ 11.1 mmol/L predicted all-cause mortality better than a fasting glucose level ≥ 7.0 mmol/L

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ACP J Club. 2000 Mar-Apr;132:70. doi:10.7326/ACPJC-2000-132-2-070


Source Citation

Glucose tolerance and mortality: comparison of WHO and American Diabetes Association diagnostic criteria. The DECODE study group. European Diabetes Epidemiology Group. Diabetes Epidemiology: Collaborative analysis Of Diagnostic criteria in Europe. Lancet. 1999;354:617-21. [PubMed ID: 10466661]


Abstract

Question

What is the relative accuracy of fasting plasma glucose (FPG) levels alone (American Diabetes Association [ADA] diagnostic criteria for diabetes mellitus) compared with 2-hour glucose levels (World Health Organization [WHO] criteria) for predicting the risk for mortality associated with diabetes?

Design

Comparison of the ADA and WHO diagnostic criteria for diabetes for predicting all-cause mortality (the Diabetes Epidemiology: Collaborative Analysis of Diagnostic Criteria in Europe [DECODE] study).

Setting

13 centers in Europe.

Participants

18 048 men and 7316 women ≥ 30 years of age who had had baseline FPG levels and standard 2-hour oral glucose tolerance test (OGTT) results recorded and who were part of 13 European cohort studies. Follow-up was a median of 7.3 years.

Description of tests and diagnostic standard

Diagnostic tests were 2 different criteria for diabetes: the ADA criteria (FPG level ≥ 7.0 mmol/L or fasting glucose level ≥ 6.1 mmol/L for capillary or whole-blood samples) and the 2-hour WHO criteria (glucose level after the 2-h 75 g OGTT ≥ 11.1 mmol/L for plasma and capillary blood samples or ≥ 10.0 mmol/L for whole-blood samples). All-cause mortality was used as the diagnostic standard.

Main outcome measures

Hazard ratios (HRs) for all-cause mortality based on the 2 glucose criteria.

Main results

HRs for all-cause mortality, adjusted for age, sex, and center, were calculated for the different glucose cut points based on the ADA and WHO diagnostic criteria for diabetes and glucose intolerance. HRs were also compared with persons who had normal FPG (< 6.1 mmol/L) or normal 2-hour glucose levels (< 7.8 mmol/L) (Table). FPG levels did not predict mortality after adjustment for the 2-hour glucose level.

Conclusion

Both a fasting plasma glucose level ≥ 7.0 mmol/L and a 2-hour glucose level ≥ 11.1 mmol/L predicted all-cause mortality.

Source of funding: Novo Nordisk, Denmark.

For correspondence: Dr. J. Tuomilehto, Diabetes and Genetic Epidemiology Unit, Department of Epidemiology and Health Promotion, National Public Health Institute, Mannerheimintie 16, FIN-00300 Helsinki, Finland. FAX 358-9-4744 8338.


Table. Association between a fasting plasma glucose (FPG) level ≥ 7.0 mmol/L or a 2-hour glucose level ≥ 11.1 mmol/L and all-cause mortality in men and women*

Glucose criteria Hazard ratio (95% CI)
Men Women
FPG ≥ 7.0 mmol/L 1.75 (1.45 to 2.12) 1.77 (1.18 to 2.65)
FPG 6.1 to 6.9 mmol/L 1.21 (1.04 to 1.40) 1.09 (0.70 to 1.68)†
2-hour glucose ≥ 11.1 mmol/L 1.99 (1.63 to 2.43) 2.60 (1.84 to 3.69)
2-hour glucose 7.8 to 11.1 mmol/L 1.49 (1.30 to 1.71) 1.54 (1.17 to 2.03)

*Hazard ratio is adjusted for age, sex, and center and compares men and women with diabetes or glucose intolerance with those with a normal FPG level (< 6.1 mmol/L) and a normal 2-hour glucose level (< 7.8 mmol/L).
†Not significant.


Commentary

This European study examined the relation between glucose tolerance and mortality. The results support 2 conclusions: The new ADA criteria for diabetes based on FPG levels alone underestimate the risk for long-term mortality more than the WHO criteria, which are based on glucose levels after the 2-hour 75 g OGTT. The new ADA criteria for impaired fasting glucose levels (FPG 6.1 to 6.9 mmol/L) underestimate the risk for mortality more than the ADA or WHO criteria for impaired glucose tolerance (OGTT 7.8 to 11.1 mmol/L). Similar conclusions have been drawn in recent studies (1, 2). In the Cardiovascular Health Study of 4515 persons > 65 years of age, 22% had diabetes and impaired fasting glucose according to the ADA criteria, and 47% had diabetes and impaired glucose tolerance according to the WHO criteria (2). Therefore, the ADA criteria to determine impaired fasting glucose level have low sensitivity for predicting diabetes and cardiovascular mortality. A subgroup analysis of the study in older men and women suggests that a third of persons with undiagnosed diabetes have 2-hour glucose levels ≥ 11.1 mmol/L, and half of these have FPG levels < 7.0 mmol/L (3). A recent meta-analysis suggested that a 2-hour glucose level > 7.8 mmol/L was a better determinant of cardiovascular events than FPG levels > 6.1 mmol/L (4).

Increasing evidence suggests an association between impaired glucose tolerance and cardiovascular disease or mortality even in the absence of fasting hyperglycemia. Patients who have an impaired fasting glucose level should be further assessed by a 2-hour glucose challenge test as well as for other cardiovascular risk factors.

Om P. Ganda, MD
Harvard Medical School
Beth Israel Deaconess Medical CenterBoston, Massachusetts, USA


References

1. Tominaga M, Eguchi H, Manaka H, et al. Impaired glucose tolerance is a risk factor for cardiovascular disease, but not impaired fasting glucose. The Funagata Diabetes Study. Diabetes Care. 1999;22:920-4. [PubMed ID: 10372242]

2. Barzilay JI, Spiekerman CF, Wahl PW, et al. Cardiovascular disease in older adults with glucose disorders: comparison of American Diabetes Association criteria for diabetes mellitus with WHO criteria. Lancet. 1999;354:622-5. [PubMed ID: 10466662]

3. Consequences of the new diagnostic criteria for diabetes in older men and women. DECODE Study (Diabetes Epidemiology: Collaborative Analysis of Diagnostic Criteria in Europe). Diabetes Care. 1999;22:1667-71. [PubMed ID: 10526732]

4. Coutinho M, Gerstein HC, Wang Y, Yusuf S. The relationship between glucose and incident cardiovascular events. A metaregression analysis of published data from 20 studies of 95, 783 individuals followed for 12.4 years. Diabetes Care. 1999;22:233-40. [PubMed ID: 10333939]