Table 1.
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.