Oral glucose tolerance test in general practice--when is it worthwhile?
OBJECTIVE
To examine the probability of impaired glucose tolerance and diabetes, diagnosed with oral glucose tolerance test, at different levels of fasting blood glucose.


METHODS
When indicated, fasting capillary whole blood glucose was measured. Patients with blood glucose ranging from 4.4 to 6.6 mmol/l had an oral glucose tolerance test.


METHODS
General practice.


METHODS
355 patients had an oral glucose tolerance test.


RESULTS
33% had impaired glucose tolerance and 12% had diabetes. One or more diabetics were found at every level of fasting blood glucose. The probability of finding a diabetic was ten times larger in the fasting blood glucose stratum 6.1 to 6.6 mmol/l than in the fasting blood glucose stratum 4.4 to 4.9 mmol/l. Likelihood ratio increased 30 times from the lowest to the highest stratum. No cutoff point in the interval 4.4 to 6.6 mmol/l had both a high sensitivity and a high specificity for the diagnosis of diabetes.


CONCLUSIONS
If it is of great importance to find every patient with impaired glucose tolerance and diabetes, one has to do an oral glucose tolerance test in every fraction of the fasting blood glucose range 4.4 to 6.6 mmol/l (according to WHO's diagnostic criteria). Using 5.2 mmol/l as a cutoff point for an oral glucose tolerance test, the sensitivity is still high (0.95), but one would miss a few with diabetes.
Rutle
O
O
Department of General Practice, University of Oslo, Norway.
Bruusgaard
D
D
Furuseth
K
K
Vaaler
S
S
D000293:Adolescent; D000328:Adult; D000368:Aged; D003920:Diabetes Mellitus / Q000097:blood*; D005194:Family Practice; D005260:Female; D005951:Glucose Tolerance Test; D006801:Humans; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D012680:Sensitivity and Specificity