Point: A Glucose Tolerance Test Is Important for Clinical Practice

There is no doubt that clinical, symptomatic diabetes is a risk factor for cardiovascular disease (CVD) and all-cause mortality. It has also been shown that the risk is graded across the entire range of hyperglycemia (1,2). However, it has been debated during the last decades whether asymptomatic, unrecognized diabetes, or even a lesser degree of hyperglycemia, increases the risk of CVD and death. Traditionally, investigators who studied the association between hyperglycemia and the development of diabetic complications focused on fasting glucose levels (3). Until the 1980s, the standards for measuring blood glucose concentration varied, HbA1c was not available, and consequently, the results between the studies were conflicting. Now that we have data from the multitude of studies in which recommended standards have been applied (4,5), it has been possible to get a clearer picture of the matter. A plethora of recent studies from diverse populations have demonstrated that asymptomatic hyperglycemia is an independent risk factor (6–10). Hyperglycemia, however, is not a simple issue. Blood glucose has a strong diurnal variation; it also varies seasonally and changes with age. Hyperglycemia can be determined at least in three ways by measuring fasting glucose, postchallenge (or postprandial) glucose, and HbA1c. The first is by definition the lowest glucose level during the day, during a few early morning hours. HbA1c indicates the mean glycemic level during a lengthy period of time—several weeks or months—summarizing both fasting and postprandial glucose levels. Postchallenge glucose level shows the magnitude of glucose elevation (peak) after the glucose load, lasting 1–3 h. If one eats the usual three meals a day, the postprandial glycemia usually lasts from 6 to 9 h a day (11). Even though there are moderate correlations between these parameters of glycemia, in the general …