Point: A Glucose Tolerance Test Is Important for Clinical Practice

OBJECTIVE -To evaluate screening strategies based on fasting plasma glucose (FPG), clinical information, and the oral glucose tolerance test (OGTT) for detection of diabetes or other hyperglycemic states-impaired fasting glucose (IFG) and impaired glucose tolerancemeriting clinical intervention. RESEARCH DESIGN AND METHODS -We studied 8,286African-American and white men and women without known diabetes, aged 53-75 years, who received an OGTT during the fourth exam of the Atherosclerosis Risk in Communities Study. Using a split sample technique, we estimated the diagnostic properties of various clinical detection rules derived from logistic regression modeling. Screening strategies utilizing FPG, these detection rules, and/or the OGTT were then compared in terms of both the fraction of hyperglycemia cases detected and the sample fraction receiving different screening tests and identified as screen positive.RESULTS -Screening based on the IFG cut point (Ն6.1 mmol/l), followed by a clinical detection rule for those below this value, detected 86.3% of diabetic case subjects and 66.0% of all hyperglycemia cases, identifying 42% of the sample as screen positive. Applying an OGTT for those positive by the rule provides diagnostic labeling and reduces the fraction that is screen positive to 29%. Another strategy, to apply an OGTT to those with an FPG cut point between 5.6 and 6.1 mmol/l, also identifies 29% of the sample as screen positive, although it detects slightly fewer hyperglycemia cases.CONCLUSIONS -Screening strategies based on FPG, complemented by clinical detection rules and/or an OGTT, are effective and practical in the detection of hyperglycemic states meriting clinical intervention. Diabetes Care 26:1338 -1343, 2003T ype 2 diabetes is a leading cause of morbidity and mortality, and prevention of diabetes and its associated burden has become a major health priority worldwide (1). Recent clinical trials demonstrated that lifestyle interventions in individuals with impaired glucose tolerance (IGT) can prevent the development of diabetes (2-4), providing a rationale for screening IGT. Although screening these hyperglycemic states will inevitably find cases of undiagnosed diabetes and impaired fasting glucose (IFG), benefit from their early detection and treatment has not been directly documented with randomized trials.The American Diabetes Association recommended considering opportunistic screening for glucose abnormalities using either fasting glucose or the oral glucose tolerance test (OGTT) in individuals aged Ն45 years (5). It has strongly recommended screening in those with BMI Ն25 kg/m 2 , while recognizing that screening characteristics could be improved with additional clinical information. Postchallenge hyperglycemia has been shown in large observational studies to be more predictive of cardiovascular events and death than fasting hyperglycemia (6,7), although the marginal gain in prediction of cardiovascular risk obtained from the OGTT may be small (8,9).Thus, the purpose of this study is to evaluate...

Section: Research Design and Methods -The Atherosclerosismentioning

confidence: 99%

Detection of Undiagnosed Diabetes and Other Hyperglycemia States

Schmidt¹,

Duncan²,

Vigo³

et al. 2003

“…However, questions still remain regarding the ultimate clinical impact or value of detecting diabetes or IGT when the FPG is normal. These uncertainties have led to opposing editorial positions (68,69) on which test to use. The evidence still precludes definitively declaring either test more advantageous than the other.…”

Section: )mentioning

confidence: 99%

Follow-up Report on the Diagnosis of Diabetes Mellitus

2003

3,051

727

“…The metabolic abnormalities of the postprandial phase are more relevant risk markers than previously thought (15,16), and the benefits of preventive strategies tested in people with IGT may be partly due to the correction of postprandial hyperglycemia (17). Even though OGTT is nonphysiological and postchallenge glucose is not the same as glucose after a mixed meal, it can be a better proxy than IFG for the hyperglycemic spikes occurring in the postprandial phase in nondiabetic people (18). Performing OGTT in people with fasting glucose of 5.7-6.9 mmol/l, as recommended by the Canadian Diabetes Association, would help with risk stratification and targeting of intervention in people with IFG, particularly when other risk factors for diabetes or IGT are present (9,19).…”

mentioning

confidence: 99%

Changing the Definition of Impaired Fasting Glucose

Vaccaro

Riccardi²

2005

OBJECTIVE -This study evaluates the impact of lowering the diagnostic threshold for impaired fasting glucose (IFG) from 6.1 to 5.6 mmol/l as proposed by the American Diabetes Association (ADA) on the prevalence of the condition, classification of individuals, and risk definition. RESEARCH DESIGN AND METHODS -A total of 1,285 employees of the ItalianTelephone Company aged 35-59 years without known diabetes underwent an oral glucose tolerance test (OGTT). BMI, serum cholesterol, triglycerides, and blood pressure were measured. Medication use was recorded.RESULTS -With the new ADA criterion, the proportion of people diagnosed with IFG increased from 3.2 to 9.7%. The newly proposed IFG category identified 41% of all subjects with impaired glucose tolerance (IGT) compared with 16.2% identified with the use of the World Health Organization criterion for IFG; the improvement in accuracy has been achieved at the cost of classifying more previously "normal" subjects as having IFG (from 2.3 to 7.3%). Both IFG and IGT were associated with an unfavorable risk profile for diabetes and cardiovascular disease, with a higher estimated risk for IGT than IFG.CONCLUSIONS -Even with the revised diagnostic criterion, IFG and IGT identify distinct groups that have a different background risk. The cost/benefit of preventive measures tested in people with IGT may not apply to the new IFG category. Diabetes Care 28:1786 -1788, 2005T he American Diabetes Association (ADA) Expert Committee on the Diagnosis and Classification of Diabetes Mellitus has recommended lowering the diagnostic threshold of impaired fasting glucose (IFG) from 6.1 to 5.6 mmol/l (1). The advantages of this change as reported by the committee (1) have been questioned (2,3). Impaired glucose tolerance (IGT) and IFG, as defined by the World Health Organization (WHO) (4), differ in various aspects: IGT is more prevalent than IFG, and postchallenge hyperglycemia is more closely associated with a risk of developing diabetes and cardiovascular disease (CVD) (5-7) than fasting hyperglycemia. Lowering the diagnostic glucose threshold for IFG to 5.6 mmol/l would supposedly result in a similar prevalence of IFG and IGT and increase the concordance between the two groups with respect to risk definition (1). Application of the lower diagnostic threshold would increase the prevalence of IFG, and this has indeed been demonstrated in various, mostly nonwhite populations (3,8). To what extent this would also enhance alignment between IFG and IGT in the classification of individuals and, more importantly, in the definition of risk for diabetes and CVD is less clear and is relevant for the implementation of preventive strategies.The present analysis was undertaken to evaluate to what extent lowering the IFG diagnostic threshold would increase the concordance between the IFG and IGT categories with regard to classification of individuals, cardiovascular risk, and risk of progression to diabetes in an Italian population of white adults.RESEARCH DESIGN AND METHODS -Our analysis was conduc...