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Diagnosis of Gestational Diabetes Mellitus (GDM) in Australia

28 April 2016

For over 20 years, the diagnosis of GDM in Australia has been derived from an ad hoc consensus, based on very limited data available at that time.1   The landmark observation trial HAPO, 20082 and other important randomised trials (Crowther et al. 20053; Langdon et al. 20094) have led to recommendations for new criteria for the diagnosis of GDM5, which have been endorsed by the World Health Organisation (WHO).

Locally, these criteria have been endorsed by the Australasian Diabetes in Pregnancy Society (ADIPS) and the Australian Diabetes Society (ADS) but not by the Endocrine Society of Australia (ESA) or the Society of Obstetric Medicine of Australia and New Zealand (SOMANZ).  The result is that there are currently two sets of GDM diagnostic criteria in use – causing significant confusion amongst obstetricians, midwives, pathologists and patients.

On 1 November 2013, RANZCOG convened a multidisciplinary working party to progress the issue of variation in diagnosis of GDM (the Australian Multidisciplinary Gestational Diabetes Working Party). This working party included representation from:

  • The Royal Australian and New Zealand College of Obstetricians and Gynaecologists (RANZCOG),
  • The Australasian Diabetes in Pregnancy Society (ADIPS),
  • The International Association of the Diabetes and Pregnancy Study Groups (IADPSG),
  • The Royal College of Pathologists of Australasia (RCPA),
  • The Australian College of Midwives (ACM),
  • The Australian Diabetes Educators Association (ADEA),
  • The Australian Diabetes Society (ADS),
  • The Society of Obstetric Medicine of Australia and New Zealand (SOMANZ), and
  • Consumer representation.

Representatives from the Endocrine Society of Australia (ESA), The Australian College of Rural and Remote Medicine (ACRRM) and the Royal Australian College of General Practitioners (RACGP) were invited to attend but sent their apologies.

Following extensive review of implementation issues surrounding variable gestational diabetes diagnostic criteria, a key finding of the working party was that the current “two-step” process of an oral glucose challenge test (OGCT) at 28 weeks followed with an oral glucose tolerance test (OGTT) is inaccurate and inefficient. This two-step process misses 25% of cases of GDM and results in almost 30% of patients being “chased up” and recalled for a second test.

The working party recommended that by 1 July 2014, health services and practitioner should transition to single step testing with a 75g OGTT at 24-28 weeks’, replacing the practice of OGCT followed by OGTT. This is recommended because:

1. Up to 25% of GDM is missed by the two-step process

2. Diagnosis and therapy of GDM is delayed by the two-step process, sometimes beyond 30 weeks’ due to delays in arranging for and performing the second test.

3. Some women do not ever get to do the second test when indicated

4. Health services will be able to accurately determine the incidence of GDM.

A further recommendation of this Working Party is to aim for adoption of WHO-2013 diagnostic criteria by 1 Jan 2015.

Motions (passed by RANZCOG Council, March 2014)

  1. A single step OGTT at 24-28 weeks be implemented by 1 July 2014, and
  2. The target for adoption of WHO- 2013 diagnostic criteria is 1 Jan 2015.

References

1. Martin FI. The diagnosis of gestational diabetes. Ad Hoc Working Party. Med J Aust. 1991;155(2):112.
2. Metzger BE, Lowe LP, Dyer AR, Trimble ER, Chaovarindr U, Coustan DR, et al. Hyperglycemia and adverse pregnancy outcomes. N Engl J Med. 2008;358(19):1991-2002.
3. Crowther CA, Hiller JE, Moss JR, McPhee AJ, Jeffries WS, Robinson JS. Effect of treatment of gestational diabetes mellitus on pregnancy outcomes. N Engl J Med. 2005;352(24):2477-86.
4. Landon MB, Spong CY, Thom E, Carpenter MW, Ramin SM, Casey B, et al. A multicenter, randomized trial of treatment for mild gestational diabetes. N Engl J Med. 2009;361(14):1339-48.
5. Metzger BE, Gabbe SG, Persson B, Buchanan TA, Catalano PA, Damm P, et al. International association of diabetes and pregnancy study groups recommendations on the diagnosis and classification of hyperglycemia in pregnancy. Diabetes Care. 2010;33(3):676-82.




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Diagnosis of Gestational Diabetes Mellitus (GDM) in Australia

For over 20 years, the diagnosis of GDM in Australia has been derived from an ad hoc consensus, based on very limited data available at that time.

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