Screening for gestational diabetes: the time of day is important

To the Editor: The 50 g glucose challenge test (GCT) is widely recommended as a screening test for gestational diabetes (GD).1 The test consists of a 50 g oral glucose load given at any time of the day, followed one hour later by the measurement of the plasma glucose concentration.2 This test is recognised as imperfect for screening, as sensitivity and specificity are not 100%.2,3 It is known that glucose tolerance deteriorates in the afternoon,4 which raises the question of whether time of day influences the response to the 50 g GCT.