Comparison of differing diagnostic criteria for diabetes: experience from a New Zealand community laboratory.
OBJECTIVE
To compare rates of diabetes and impaired glucose tolerance in oral glucose tolerance tests (OGTTs) from a New Zealand community laboratory applying differing diagnostic criteria.


METHODS
Results from 455 non-pregnant subjects in 75 g oral glucose tolerance tests were reviewed with diabetes assigned according to 1985 WHO criteria (either fasting plasma glucose (FPG) > or =7.8 mmol/L or two-hour glucose > or =11.1 mmol/L), the American Diabetes Association (ADA) criteria (FPG > or =7.0 mmol/L alone), or revised WHO criteria (adopted by the Australasian Working Party) for OGTT (either FPG > or =7.0 mmol/L or 2-h value of > or =11.1 mmol/L). Impaired glucose tolerance (IGT) was assigned according to 1985 WHO criteria (FPG <7.8 mmol/L and 2-h glucose > or =7.8 mmol but <11.1 mmol/L), impaired fasting glucose (IFG) according to the ADA criteria (FPG of > or =6.1 but <7.0 mmol/L), or combination of IFG and IGT (revised WHO criteria).


RESULTS
The 1985 WHO criteria assigned 266 cases (58.5%) as normal glucose tolerance (NGT), 93 (20.4%) as IGT and 96 (21.1%) as diabetic. The ADA fasting criterion assigned 299 (65.7%) as NGT, 82 (18%) as IFG and 74 (16.2%) as diabetic. Only 55 (47.8%) cases identified as diabetic by either criterion met both. Using the combination of FPG > or =7.0 mmol/L or the 2-h glucose of > or =11.1 mmol/L (revised WHO criteria), 115 (25.3%) were assigned as diabetic, 102 (22.4%) as IFG or IGT, and 238 (52.3%) as NGT.


CONCLUSIONS
There is thus a 22.9% decrease in diabetes with the ADA fasting criterion, compared with the 1985 WHO criteria. With revised WHO criteria (as adopted by the Australasian Working Party), there is a 19.8% increase in diabetes and a 9.7% increase in those with IFG/IGT. These figures have resource implications for the management of diabetes in New Zealand.
Florkowski
C
C
Southern Community Laboratories, Christchurch. cflorkowski@chmeds.ac.nz
Thompson
A
A
D000293:Adolescent; D000328:Adult; D000368:Aged; D001786:Blood Glucose / Q000378:metabolism*; D019411:Clinical Laboratory Techniques / Q000592:standards; D003924:Diabetes Mellitus, Type 2 / Q000145:classification / Q000175:diagnosis*; D005215:Fasting / Q000378:metabolism*; D005951:Glucose Tolerance Test; D006801:Humans; D008875:Middle Aged; D009520:New Zealand
D001786:Blood Glucose