Abstract
Objectives
To compare the prevalence and metabolic profiles of glucose tolerance categories according to World Health Organization(WHO) and 1997 American Diabetes Association (ADA) fasting criteria for the diagnosis of diabetes mellitus and impaired glucose metabolism in the Korean population.
Methods
2251 subjects without previous history of diabetes, who participated in the Yonchon diabetes epidemiology survey in 1993, were classified according to both criteria. The prevalence of glucose tolerance categories and the agreement across all categories of glucose tolerance were calculated. Metabolic characteristics of different glucose tolerance categories were compared.
Results
The prevalence of diabetes and impaired fasting glucose (IFG) according to ADA fasting criteria was similar to those of diabetes and impaired glucose tolerance (IGT) according to WHO criteria, respectively. However, 35.5 % of the subjects who were diagnosed as diabetes by WHO criteria were reclassified as either IFG or normal fasting glucose (NFG), and 38.5 % of diabetic patients according to ADA fasting criteria were IGT or normal glucose tolerance (NGT) by WHO criteria. Only 31.3 % of IGT subjects remained as IFG and 62.1 % were reclassified as NFG. Similarly, 69.4 % of IFG subjects were NGT by WHO criteria. The agreement between the two criteria was poor (K =0.31).
Discordant diabetes groups had higher WHR, systolic and diastolic blood pressure, cholesterol and triglyceride levels than concordant non-diabetes group. Non-diabetes(WHO)/diabetes(ADA) group had higher WHR than diabetes (WHO)/non-diabetes (ADA) group. There were no differences in other metabolic characteristics between the two discordant diabetes groups. IGT/NFG and NGT/IFG group showed higher BMI, WHR, systolic and diastolic blood pressure, cholesterol and triglyceride levels than NGT/NFG group. Metabolic characteristics of IGT/NFG group were not different from those of NGT/IFG group except IGT/NFG subjects were older than NGT/IFG subjects.
Conclusion
The agreement between WHO and ADA fasting criteria was poor. ADA fasting criteria can detect new diabetic patients and subjects with impaired glucose metabolism who are not classified as diabetes or IGT by WHO criteria. However, a substantial number of subjects, who may have increased cardiovascular risk and/or increased risk for the development of diabetes and its complication, will be missed when using ADA fasting criteria.
Keywords: Diagnosis, Diabetes mellitus, Impaired glucose tolerance, Impaired fasting glucose, Fasting plasma glucose
INTRODUCTION
Diagnosis of diabetes mellitus has been based on fasting plasma glucose(FPG) value and glucose value measured 2 h after a standard 75 g glucose load(2-h PG).1,2) The cutpoint of these criteria is based mainly on the prevalence of microvascular complications. However, FPG cutpoint of 140 mg/dL has been challenged since it defined a greater degree of hyperglycemia than did the cutpoint of 2-h PG(200 mg/dL).3) Recently, American Diabetes Association(ADA) has proposed a revised diagnostic criteria that lowers the FPG cutpoint to 126 mg/dL.4) By lowering FPG cutpoint, cutpoints for the FPG and 2-h PG are believed to diagnose similar conditions, and ADA recommends that the FPG test is greatly preferred in clinical settings because of ease of administration, convenience, acceptability to patients and lower cost.
It is well established that diabetes mellitus and impaired glucose tolerance by WHO criteria(1985) are also associated with an increased risk of development of cardiovasular disease and form part of the metabolic syndrome.5) At present, it is not clear whether metabolic characteristics of glucose tolerance categories based on FPG criteria are in agreement with those of WHO criteria(1985) or not. Larsson et al.6) reported that the subjects with IGT and IFG are comparable in terms of body mass index, blood pressure and serum lipids in a group of middle-aged Caucasian women, while Gimeno et al.7) showed that subjects with discordant diagnoses, who had IGT or diabetes by WHO criteria but who were normal by ADA fasting criteria, exhibited a higher number of cardiovascular risk factors (higher blood pressure and triglyceride and low HDL cholesterol) than those who were discordant (IFG/diabetes) by ADA fasting criteria but normal by WHO criteria.
In this study, we applied the revised ADA fasting criteria to data collected from a previously published population-based survey for diabetes in Korean subjects8,9) and compared the prevalence and metabolic profile of glucose tolerance categories with those of WHO criteria.
RESEARCH DESIGN AND METHODS
The Yonchon Study is a population-based diabetes epidemiology survey in the Korean population. The study population and research design have been described in detail, previously.8,9) Subjects were classified according to both WHO criteria and 1997 ADA fasting criteria. Subjects who were already using oral hypoglycemic agents, insulin or diet for diabetes were excluded from all analyses.
Prevalence of glucose tolerance categories were calculated for both sets of diagnostic criteria and to examine the agreement between the two criteria, all categories of glucose tolerance were calculated.10) Metabolic characteristics of different glucose tolerance categories were compared. Differences among these groups were tested with analysis of variance. Statistical analyses were done using the Statistical Packages for Social Science(SPSS) 8.0 for windows. P-values <0.05 (two-tailed) were considered to be statistically significant.
RESULTS
1. Prevalence of glucose tolerance categories
The overall prevalence of diabetes did not differ between the two criteria. Prevalence of diabetes according to WHO(1985) criteria was 5.15 % and that according to ADA(1997) fasting criteria was 5.42 %. However, only 64.7%(75 of 116 subjects) of those who were diagnosed as diabetes according to WHO criteria were diagnosed as diabetes by ADA fasting criteria. 19.0 % of diabetes according to WHO criteria were reclassified as impaired fasting glucose(IFG) and 16.4 % as normal fasting glucose(NFG). Similarly, 38.5 % of diabetic patients according to ADA fasting criteria were IGT or normal glucose tolerance(NGT) by WHO criteria(Table 1).
Table 1.
Agreement between WHO(1985) and ADA (1997) Diagnostic Criteria: the Yonchon Study
| WHO (1985) | ||||
|---|---|---|---|---|
| NGT | IGT | Diabetes | Combined | |
| AFG | 1591 | 169 | 19 | 1779 |
| IFG | 243 | 85 | 22 | 350 |
| Diabetes | 29 | 18 | 75 | 122 |
| Combined | 1863 | 272 | 116 | 2251 |
NGT: normal glucose tolerance, IGT: impaired glucose tolerance, NFG: normal fasting glucose, IFG: impaired fasting glucose
The prevalence of IFG was 15.1%, while the prevalence of IGT was 12.1%. Only 31.3 %(85 of 272 subjects) of IGT subjects remained as IFG and 62.1 %(169 of 272 subjects) were reclassified as NFG and 6.8 %(18 of 272 subjects) as diabetes. Only 24.3 % of IFG subjects were IGT by WHO criteria and 69.4 % were NGT by WHO criteria.
The agreement between the two criteria for the diagnosis of previously unknown diabetes was poor (K = 0.31)
2. Metabolic profiles of glucose tolerance categories
Concordant and discordant diabetes groups were older than concordant non-diabetes group. They showed higher WHR, systolic and diastolic blood pressure, cholesterol and triglyceride levels than concordant non-diabetes group (Table 2). When comparing metabolic characteristics among diabetes groups, concordant diabetes [diabetes (WHO) / diabetes (ADA)] group showed higher triglyceride and lower HDL levels than discordant diabetes groups. Non-diabetes (WHO)/ diabetes (ADA) group had higher WHR than diabetes (WHO)/non-diabetes(ADA) group. There were no differences in other metabolic profiles between the two discordant diabetes groups.
Table 2.
Comparison of Metabolic Profile Among Diabetic Subgroups According to WHO(1985) and ADA(1997) Diagnostic Criteria
| Non-DM/Non-DM | DM(WHO)/Non-DM(ADA) | Non-DM(WHO)/DM(ADA) | DM(WHO)/DM(ADA) | |
|---|---|---|---|---|
| Age(years) | 53 ± 13 | 62 ± 14* | 59 ± 12* | 58 ± 12* |
| Sex(M:F) | 898/1190 | 21/20 | 29/18 | 44/31 |
| BMI(kg/m2) | 23.9 ± 3.3 | 24.8 ± 3.8 | 23.7 ± 3.3 | 25.3 ± 3.9* |
| WHR | 0.86 ± 0.06 | 0.90 ± 0.05*† | 0.94 ± 0.17* | 0.91 ± 0.09*† |
| systolic BP(mmHg) | 125 ± 21 | 139 ± 27* | 133 ± 22* | 136 ± 19* |
| diastolic BP(mmHg) | 80 ± 13 | 88 ± 17* | 85 ± 14* | 87 ± 13* |
| Cholesterol § | 4.03 ± 0.80 | 4.42 ± 0.88* | 4.40 ± 1.03* | 4.34 ± 1.11* |
| Triglyceride § | 1.64 ± 1.16 | 2.20 ± 1.48* | 2.36 ± 1.59* | 2.83 ± 2.11*†‡ |
| HDL § | 0.96 ± 0.28 | 1.03 ± 0.41 | 0.98 ± 0.41 | 0.88 ± 0.34‡ |
mmol/L, BP:blood pressure, DM: diabetes mellitus
p < 0.05 vs Non-DM/Non-DM,
p < 0.05 vs Non-DM/DM,
p < 0.05 vs DM/Non-DM
Table 3. showed metabolic profiles of subjects with impaired glucose metabolism. Concordant and discordant impaired glucose metabolism groups were older and had higher BMI, WHR, systolic and diastolic blood pressure, cholesterol and triglyceride levels than NGT/NFG group. IGT/IFG subjects showed higher WHR and triglyceride levels than discordant impaired glucose metabolism groups(IGT/NFG, NGT/IFG). Metabolic profiles of IGT/NFG group were not different from those of NGT/IFG group, except that IGT/NFG group was older than NGT/IFG group.
Table 3.
Comparison of Metabolic Profile for Impaired Glucose Metabolism According to WHO (1985) and ADA (1997) Criteria
| NGT/NFG | IGT/NFG | NGT/IFG | IGT/IFG | |
|---|---|---|---|---|
| Age(years) | 51 ± 13 | 59 ± 11*† | 54 ± 12* | 59 ±13*† |
| Sex(M-F) | 655/936 | 62/107 | 128/115 | 50/35 |
| BMI(kg/m2) | 23.7 ± 3.1 | 24.6 ± 3.8* | 24.2 ±3.5* | 25.0 ± 3.2* |
| WHR | 0.86 ± 0.06 | 0.88 ± 0.06* | 0.87 ± 0.06* | 0.89 ± 0.06*†‡ |
| systolic BP(mmHg) | 123 ± 21 | 131 ± 23* | 129 ± 20* | 133 ±22* |
| diastolic BP(mmHg) | 79 ± 13 | 85 ± 15* | 84 ± 12* | 86 ± 14* |
| Cholesterol§ | 4.01 ± 0.78 | 4.14 ± 0.85 | 4.14 ± 0.80* | 4.27 ±0.75* |
| Triglyceride§ | 1.56 ± 1.04 | 1.83 ± 1.10* | 1.83 ± 1.46* | 2.26 ±1.91*†‡ |
| HDL§ | 0.96 ± 0.28 | 0.96 ± 0.34 | 0.96 ± 0.31 | 0.91 ±0.31 |
mmol/L BP:blood pressure, NGT:normal glucose tolerance, IGT: impaired glucose tolerance, NFG: normal fasting glucose, IFG: impaired fasting glucose
p< 0.05 vs NGT/NFG,
p < 0.05 vs NGT/IFG,
p < 0.05 vs IGT/NFG
DISCUSSION
The revised ADA diagnostic criteria are intended to reduce the discrepancy between FPG and 2-h PG cutpoint and to encourage the use of FPG rather than the oral glucose tolerance test to diagnose diabetes. In this study, the prevalence of diabetes using ADA fasting criteria was similar with that using WHO(1985) criteria. However, the agreement between WHO and ADA fasting criteria was not good. A third of the subjects who were diagnosed as diabetes according to WHO criteria were reclassified as either IFG or NFG by ADA fasting criteria. Similarly 38.5 % of the subjects who were diagnosed as diabetes by ADA fasting criteria were not diagnosed as having diabetes according to WHO criteria. Our study also showed that about 2/3 of IGT subjects were reclassified as NFG, which is very similar to previous reports showing that 70–80 % of IGT subjects were reclassified as NFG.10,11) Conversely, 2/3 of IFG subjects were NGT by WHO criteria. These results are consistent with the reports which showed only moderate to poor agreement between the two criteria.13,14)
Poor agreement between the two criteria raised the concern that a substantial number of glucose intolerant subjects, who have a increased risk of diabetic complications or increased risk of developing diabetes mellitus and cardiovascular disease, may be ignored when using ADA fasting criteria.
Our results showed that discordant diabetes groups had higher WHR, blood pressure, cholesterol and triglyceride than the concordant non-diabetes group. However, metabolic characteristics of diabetes (WHO)/non-diabetes(ADA) group was similar to those of non-diabetes(WHO)/diabetes(ADA) group. This implies that when we use ADA fasting criteria to diagnose diabetes, we will miss a similar number of subjects who may have increased risk for diabetic complications.
Subjects with IGT are known to have increased risk of developing diabetes and cardiovascular disorders.15,16) In our population, IGT/NFG subjects had increased cardiovascular risk compared to NGT/NFG subjects. Although they were older than NGT/IFG subjects, other metabolic profiles were similar to those of NGT/IFG subjects. Thus, the discordant impaired glucose metabolism group may have a similar risk for the development of diabetes and cardiovascular disease. These results are similar to the observation in a group of middle-aged Caucasian women6) while Gimeno et al.7) showed that subjects with discordant diagnoses, who had IGT or diabetes by WHO criteria but who were normal by ADA fasting criteria, exhibited a higher number of cardiovascular risk factors than those who were discordant (IFG/diabetes) by ADA fasting criteria but normal by WHO criteria. These results suggest that subjects with IGT who are reclassified as NFG by ADA fasting criteria have no less risk for development of diabetes and cardiovascular disease than subjects with NGT/IFG.
In conclusion, ADA fasting criteria can detect a similar number of diabetic patients and impaired glucose metabolism. It can pick up new subjects who are not classified as diabetes or impaired glucose tolerance by WHO criteria. However, a substantial number of subjects, who may have increased cardiovascular risk and/or increased risk for the development of diabetes, will be missed when using only FPG cutpoint. Long term study will be needed to evaluate whether glucose tolerance categories classified by ADA fasting criteria will result in decreased morbidity and mortality, compared to those according to WHO criteria.
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