Table 1.

Advantages and disadvantages of two-step and one-step testing for GDM

Characteristic	Two-step	One-step
Method	In the two-step screening approach, a 50-g GCT followed by a 100-g, 3-hour OGTT. Those who screen positive are followed up by an oral 100-g glucose tolerance test	In the one-step screening approach, 75-or 100-g OGTT is done in all patients, without the preliminary step by GCT
Advantages	• Fewer false positives • Avoids OGTT in more than 75% of the women	• Simple to follow • Easily diagnosed
Disadvantages	• Missed diagnosis: 75% sensitivity with 84% specificity as compared with single-step 100-g OGTT • Delay in initiating treatment even in those who test positive • It requires patients to make two visits for testing, where GCT is not feasible throughout the day	• Poor reproducibility • All women need to come in fasting state

Abbreviations: GDM, gestational diabetes mellitus; GCT, glucose challenge test; OGTT, oral glucose tolerance test.