THE REPRODUCIBILITY AND USEFULNESS OF THE ORAL GLUCOSE-TOLERANCE TESTIN SCREENING FOR DIABETES AND OTHER CARDIOVASCULAR RISK-FACTORS

We examined the reproducibility of oral glucose tolerance tests (OGTT) using the World Health Organization criterion in 212 Chinese subjects (male 149, female 63) who underwent two 75g OGTTs within a 6-week per iod. The overall reproducibility was 65.6% (139/212) of which 74 subje cts had normal glucose tolerance, 24 had diabetes and 41 had impaired glucose tolerance (IGT) on two occasions. The subjects were divided in to three groups [group 1: normal OGTTs on both occasions (n = 74); gro up 2: one abnormal OGTT (either diabetes or IGT) (n = 51); group 3: 2 abnormal OGTTs (n = 87)]. Subjects in group 1 were younger, had lower blood pressure, body mass index (BMI), waist-to-hip ratio (WHR), fasti ng and 2h plasma insulin levels, triglyceride, very-low density lipopr otein and apolipoprotein-B concentrations than both groups 2 and 3. Gr oup 2 had similar characteristics as group 3 except for a lower glycat ed haemoglobin (HbA(lc)), string and 2h plasma glucose during the two OGTTs. With receiver operating characteristic curve (ROC) analysis, a HbA(lc) of 5.3% gave an optimal sensitivity of 70.7% and specificity o f 74.3% to predict diabetes as defined by a 2h plasma glucose value gr eater than or equal to 11.1 mmol/L in the first OGTT. Of the 212 subje cts, 73 had HbA(lc) greater than or equal to 5.3%. The reproducibility of OGTT was 56.2% for these 73 subjects. With ROC analysis, a BMI of 25 kg/m(2) gave an optimal sensitivity of 53.7% and specificity of 56. 7% to predict diabetes. For the 36 subjects with BMI greater than or e qual to 25 kg/m(2), reproducibility of OGTT was 58.3%. Similarly, for the 140 subjects with WHR greater than or equal to 0.9, the reproducib ility of OGTT was 57.9%. These findings confirmed the poor reproducibi lity of OGTT which was not improved even amongst subjects HbA(lc), BMI or WHR. Furthermore, subjects with one abnormal OGTT, whether reprodu cible or not, had a higher cardiovascular risk profile compared to sub jects who had two normal OGTTs.