Final answer:
The criteria for testing for early GDM involves conducting a glucose tolerance test (GTT) in patients suspected of having diabetes. If GTT is positive for diabetes mellitus, further investigations can be done to determine the type of diabetes through an Insulin Tolerance Test (ITT) and a Glucagon Tolerance Test (GuTT).
Step-by-step explanation:
Early testing for gestational diabetes mellitus (GDM) involves conducting a glucose tolerance test (GTT) in patients suspected of having diabetes. GTT is performed in individuals who do not show any glucosuria but have a high renal threshold for glucose or have blood glucose levels that are within the normal range but around the lower end. The test helps to determine the presence of hyperglycemia, which is observed during the GTT.
If GTT results are positive and the patient is confirmed to have diabetes mellitus, further investigations are required to determine the type of diabetes, whether it is insulin-dependent or insulin-independent. This can be done through an Insulin Tolerance Test (ITT) and a Glucagon Tolerance Test (GuTT). In an ITT, patients with Insulin Dependent Diabetes Mellitus (IDDM) will show relative hypoglycemia compared to the initial glucose level.