Changing the definition of impaired fasting glucose: impact on the classification of individuals and risk definition.
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.


METHODS
A total of 1,285 employees of the Italian Telephone 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.
Department of Clinical and Experimental Medicine, University of Naples Federico II, Via S Pansini 5, 80131 Napoli, Italy. ovaccaro@unina.it
Olga
O
Vaccaro
Gabriele
G
Riccardi
D000328:Adult; D000367:Age Factors; D001786:Blood Glucose / Q000032:analysis*; D001794:Blood Pressure; D015992:Body Mass Index; D002318:Cardiovascular Diseases / Q000453:epidemiology*; D005215:Fasting; D018149:Glucose Intolerance / Q000097:blood / Q000145:classification* / Q000453:epidemiology; D006306:Health Surveys; D006801:Humans; D007558:Italy / Q000453:epidemiology; D008403:Mass Screening / Q000379:methods; D008875:Middle Aged; D012307:Risk Factors; D013689:Telephone
D001786:Blood Glucose