How to Identify Prediabetes?

Tests shall be performed to determine whether or not someone has prediabetes. The tests include the fasting blood sugar, conducted 2 hours after eating, and HbA1c tests.

- Fasting Blood Glucose

Blood sampling for this test is taken after 8-10 hours fasting. A fasting blood glucose level from 100-125 mg/dL indicates prediabetes because of the Impaired Fasting Glucose (IFG).

- Oral Glucose Tolerance Test

Blood sampling for this test is taken 2 hours after the administration of 75 g glucose in 300 ml of water. A blood glucose level from 140 to 199 mg/dL indicates prediabetes because of the Impaired Glucose Tolerance (IGT).

- Hemoglobin A1c (HbA1c)

Blood sampling for this test can be done anytime. An A1c level between 5.7 and 6.4% indicates prediabetes.

Diabetes prevention is the only way to reduce its occurrence and complications. Lifestyle intervention (calorie intake restriction and moderate-intensity physical activity) for those with prediabetes is useful to prevent the development of diabetes and type 2 diabetes. This intervention is more beneficial compared to prevention by medication. Medication has several downsides such as high toxicity, low tolerability, high cost, and low efficiency.

Many epidemiological studies have not yet employed the method of glucose test 2 hours after having glucose administration to establish prediabetes diagnosis and only used the result of fasting blood glucose test. This method cannot detect the IGT condition, which later may lead to a false negative result. Meanwhile, when someone with normal fasting blood glucose takes OGTT, the result may indicate an IGT case. It is necessary to detect IGT since the risk of developing T2DM and cardiovascular complication is higher for people with IGT than those with IFG.

The pathophysiology of prediabetes is usually based on the changes in insulin sensitivity and b-pancreas functions. IGT and IFG show different pathophysiologic mechanisms for the two conditions. IGT and IFG occurs due to insulin resistance, but both happen in different place within the body. Insulin resistance in those with IFG mainly happens within the liver tissue, while the insulin sensitivity within the muscle tissue is normal. In the cases of IGT, the insulin sensitivity within the liver tissue is normal or slightly decreased, while the insulin resistance happens to the muscle tissue.

Additionally, both conditions have different insulin secretion patterns. In GPT, there is a decrease of first phase insulin secretion (the first 10 minutes) after the administration of intravenous glucose and a decrease of first phase insulin secretion response (the first 30 minutes) after the administration of oral glucose. Whereas the prolonged phase of insulin secretion (60-120 minutes) is normal during OGTT. In IGT, there is also a disrupted first phase insulin secretion after the administration of oral glucose followed by a significant decrease of final phase insulin secretion.

HbA1c test has been recommended by ADA as an alternative analysis in diagnosing diabetes (> 6.5%) as well as to detect the increased risk of diabetes or prediabetes (5.7-6.4%). Currently, HbA1c is recognized as a better marker than blood glucose in predicting the mortality and cardiovascular risk in those who are non-diabetic. However, there is only a number of studies that proved the statement and there are other opinions saying that the result cannot be as good as the one obtained from the 2 hour postprandial glucose test. HbA1c, fasting blood glucose, and 2 hour blood glucose assess glucose metabolism aspects differently, but the difference of these three glycemic in assessing the insulin resistance, insulin secretion, and other metabolic abnormalities still remains unclear.