Which of the following tests are used to screen for gestational diabetes in a 22 year old primigravida?

Glucose challenge test (GCT) is commonly used in screening for gestational diabetes. No special preparation is needed for this test. Fifty grams of oral glucose is given between 24-28 weeks of gestation irrespective of the time or the meal and blood glucose is determined 1 hour later. A plasma value of 140 mg/dl is considered significant to perform the confirmatory diagnostic test. Ref: Essential of Obstetrics By Arulkumaran, 2004, Page 149 ; Dutta, 6th ed, Page 285