Investigation Of Clinical Application Value And Strategy Of Oral Glucose Tolerance Test

Oral glucose tolerance test (OGTT) is standard screening method for impaired glucose regulation (IGR) and diabetes mellitus (DM). However, it remains debate about the role of OGTT in population screening due to poor reproducibility, inconvenience and high cost. First of all, the reproducibility of OGTT was explored by two OGTTs performed in 259 subjects without previously diagnosed DM over a period of 2-3 weeks in our study. The clinical application value of OGTT was evaluated by the results of repeated OGTTs. Two kinds of diabetes risk scores (DRS) were developed basing on medical materials of middle-aged or old-aged adults living in Beijing by Logistic regression and their efficacies of predicting DM were evaluated by receiver operating curve. Finally, clinical application strategy of OGTT was explored for screening abnormal glucose metabolism in population.The overall reproducibility was 55.6% according to the criteria of ADA 2008 and 59.1% according to the criteria of WHO 2006. The reproducibility was lower in subjects with over 55-year-old than subjects with below 55-year-old (P<0.05). Subjects with IGR showed lower reproducibility (34.7%-36.1%), as compared with those with normal glucose tolerance (NGT) (90.9%-91.2%) and newly diagnosed DM (63.8%)(P<0.05). The reproducibility of OGTT in subjects with two and more than two components of metabolic syndrome (MS) according the criteria of Chinese Diabetes Society (CDS) is lower than those with less than two components of MS (P<0.05). Logistic regression analysis showed that the time of drawing blood was independent risk factor of reproducibility of OGTT.In two tests, prevalences of DM and IGR were respectively 5.79%-8.11% and 30.1%-38.2% only using FPG, 15.1%-18.5% and 44.8%-56.4% using one OGTT, 21.2% and 54.8% using two OGTTs. According to the results of the two OGTTs, non-diabetes mellitus (NDM)/DM group and NGT/IGR group respectively had older age, higher blood pressure, waist circumference and waist-hip-ratio (WHR) than NDM/NDM group and NGT/NGT group (P<0.05). However, NDM/DM group and NGT/IGR group respectively had similar clinical characteristics with DM/DM group and IGR/IGR group. According to the criteria of IDF or CDS, prevalence of MS was higher in NDM/DM group and NGT/IGR group, comparing with NDM/NDM group and NGT/NGT group (P<0.05). NDM/DM group showed higher prevalence of obesity and dyslipidemia than NDM/NDM group, and NGT/IGR group showed higher prevalence of hypertension than NGT/NGT group (P<0.05).DRS1 derived from cohort materials inlucded age, hypertension, history of impaired glucose tolerance (IGT), body mass index (BMI), elevated FPG, hypertriglyceridemia and hypo-high-density-lipoproteinemia. To predict incident DM, the area under the receiver operating curve (AUC) was 0.734 (95% CI 0.702-0.766)-0.759(0.686-0.831). The sum score value≥4 had sensitivity of 64.5%-72.9%, specificity of 63.9%-71.6%. DRS2 derived from cross-sectional materials included age, hypertension, BMI, elevated FPG, hypertriglyceridemia and hypo-high-density-lipo-proteinemia. AUC was 0.761(0.696-0.826)-0.788 (0.761-0.815). The sum score value≥5 had sensitivity of 61.5%-63.0%, specificity of 78.1%-78.3% for predicting DM. Incidence of DM was gradually elevated with the increase of DRS1 and DRS2 (P<0.05).The sensitivities for DM and IGR were 88.8%-100.0% and 53.8%-69.1% using DRS as an initial screening for high-risk population; 87.5% and 42.2% using FPG≥5.6 mmol/L; 98.8% and 87.9% using risk factor (two or more than two positive among age, history of hyperglycemia, hypertension and waist circumference), respectively saving 75.8%-89.4%, 100% and 38.9% OGTT performance in subjects with NGT.In conclusion, these findings confirmed the poor reproducibility of OGTT which was obvious in subjects with older age, abnormal glucose metabolism or components of MS. However, prevalence of DM and IGR can be obviously increased by performance of OGTT and subjects with one abnormal OGTT had a higher level of metabolic risk factors and prevalence of MS, as compared with subjects with NGT on two OGTTs. Therefore, OGTT is still important for screening of abnormal glucose metabolism and high risk population. DRS is effective predicting DM. The use of DRS as an initial screening for high-risk group not only increases the detection of DM, but also minimizes personal costs of OGTTs. Risk factor is a simple and easily-performed screening for abnormal glucose metabolism.