Final answer:
The Glucose Tolerance Test (GTT) is a key diagnostic tool for Gestational Diabetes Mellitus (GDM), involving a three-step process with fasting and post-glucose ingestion blood sampling.
Step-by-step explanation:
The Glucose Tolerance Test (GTT) is a test used to diagnose Gestational Diabetes Mellitus (GDM), which is a type of diabetes that develops during pregnancy. The test involves a three-part process where the patient is kept on a carbohydrate-rich diet for three days prior to testing. On the day of the test, blood glucose is measured after a fasting period and then every half hour after the ingestion of a glucose solution. The solution usually contains 50-60 grams of glucose in 300 ml of water, which equates to either 0.75 grams per kg body weight for an Indian adult male or 1.0 gm/kg body weight for individuals in developed countries. The criteria for diagnosing GDM with a 3-hour OGTT (Oral Glucose Tolerance Test) typically involve meeting or exceeding set thresholds in at least two of the blood samples collected after glucose ingestion.
Further testing, such as the Insulin Tolerance Test (ITT) or Glucagon Tolerance Test (GuTT), may be conducted if a GTT is positive, to differentiate between types of diabetes, such as insulin-dependent or independent.