Meaning of upper limit of normal range of post-load 1-h plasma glucose level defined by oral glucose tolerance test in Japanese subjects

Abstract

Aims/Introduction: To identify upper limit post-load 1-h plasma glucose (1-h PG) after 75-g oral glucose test in a Japanese population. Materials and Methods: A total of 918 subjects were enrolled. We divided the subjects into two groups: normal 2-h post-load plasma glucose (2-h PG; <140 mg/dL) and impaired 2-h PG group (≥140 mg/dL). Results: A total of 417 subjects had normal 2-h PG and 501 had impaired 2-h PG. The receiver operating characteristic (ROC) curve showed that the optimal cut-off value of 1-h PG was 179 mg/dL (area under ROC curve = 0.89), providing that the sensitivity, specificity, and positive and negative predictive value were 85, 79, 82 and 83%, respectively. The subjects with 1-h PG < 179 mg/dL consisted of 0.5% diabetes and 99.5% non-diabetes, whereas those with 1-h PG ≥ 179 mg/dL consisted of 26.9% diabetes and 73.1% non-diabetes (P < 0.01). Furthermore, there was a significant correlation between 1-h PG and 2-h PG (r2 = 0.57, P < 0.01). Conclusions: These data suggested that 179 mg/dL is the upper limit of the normal range of post-load of 1-h PG in a Japanese population. Thus, the subjects with 1-h PG ≥ 179 mg/dL might be at risk of developing future diabetes. Therefore, appropriate prospective study should be carried out to test this hypothesis. © 2013 Asian Association for the Study of Diabetes and Wiley Publishing Asia Pty Ltd.