Evidence Doesn’t Support a 1-step Approach to Diagnosing Gestational Diabetes

An independent panel convened by the National Institutes of Health has concluded that there is insufficient evidence to adopt a 1-step approach to the diagnosis of gestational diabetes mellitus (GDM).¹ The panel believes that more evidence is needed to ensure that the benefits of a 1-step diagnostic approach outweigh the harms.
   
In the United States, GDM is estimated to occur in 5% to 6% of pregnancies, but adoption of the 1-step approach, which is based on an oral glucose tolerance test (OGTT) without prior plasma or serum glucose level screening, is expected to increase the prevalence of GDM to between 15% and 20%. The possibility of potentially tripling the number of women identified as having GDM will have an enormous impact on the health care system, and the panel believes that it would be prudent to better understand the cost-benefit and cost-effectiveness of a new diagnostic protocol before changing it.
   
The 2-step diagnostic approach involves an initial measurement of plasma or serum glucose concentration 1 hour after a glucose challenge test (GCT), followed by an OGTT in women whose GCT results were above a prespecified threshold, usually 140 mg/dL or higher or 130 mg/dL or higher. The American College of Obstetricians and Gynecologists currently recommends this 2-step approach, but the American Diabetes Association and other countries support the 1-step diagnostic approach for all pregnant women.
   
From a clinical perspective, the 1-step approach offers the benefit of better standardization of patient care and allows for a diagnosis in a single office visit rather than 2 visits. The 1-step approach also seems to be cost-effective in high-risk patients, such as those with obesity, a personal history of GDM, glycosuria, or a strong family history of diabetes.²
   
Despite these potential benefits, it is unknown whether the increased number of women identified as having GDM will benefit from treatment. The panel cites research that shows that a diagnosis of GDM can result in increases in anxiety levels, the number of clinic visits, the rates of cesarean deliveries, and more intensive antenatal and neonatal assessments.¹ These unintended consequences of GDM will generate additional health care costs, and without clear evidence that a 1-step approach results in improvements in key short- and long-term outcomes, the panel currently cannot justify abandoning the current 2-step diagnostic approach.

Pertinent Points:
- Clinicians should continue using the 2-step approach to the diagnosis of gestational diabetes mellitus.
- Before adoption of a 1-step approach, more evidence is needed to demonstrate clearly that improvements in outcomes will outweigh the expected increased prevalence of and costs related to gestational diabetes mellitus.
 

References:

1. National Institutes of Health Consensus Development Panel. Diagnosing Gestational Diabetes Mellitus Conference. March 4-6, 2013. Available at: http://prevention.nih.gov/cdp/conferences/2013/gdm/files/DraftStatement.pdf. Accessed March 16, 2013.
2. American Diabetes Association. Standards of medical care in diabetes-2016. Diabetes Care. 2006;29(suppl 1):S4-S42.