The implementation of the recently published Australasian Diabetes In Pregnancy Society (ADIPS) Consensus Guidelines for the Testing and Diagnosis of Gestational Diabetes Mellitus in Australia requires two substantial changes to be made to pathology laboratory practice. These are the replacement of oral glucose challenge testing with a 2 hour 75 gram load oral glucose tolerance test (POGTT) for all pregnant patients and the application of new diagnostic cut-offs for the diagnosis of gestational diabetes mellitus (GDM).
Currently there are differences in pathology practice in Australia with some laboratories performing glucose challenge testing to screen for GDM together with applying the old ADIPS criteria to interpret the POGTT, and some endorsing the new conditions for the assessment and diagnosis of GDM. In order to fully implement the new ADIPS guidelines, it is important to ensure that a clear consensus is obtained to provide uniform guidance for laboratories and that the requisite resources are available to accommodate the increased number of patients undertaking a 2 hour oral glucose tolerance test. To this end, it would seem timely to review the various protocols that have been developed by different pathology practices for oral glucose tolerance testing so that a harmonised approach can be adopted in the performance of a POGTT.
It is also important to consider two other issues raised by the implementation of the new ADIPS guidelines. The first concerns the limited concordance between the two patient groups diagnosed with GDM using the old and new diagnostic criteria as this not only determines current management but also affects a patient’s perceived risk of type 2 diabetes and long term follow-up. The second issue involves the specimens obtained for a POGTT and whether collection conditions should reflect those which applied to the Hyperglycemia and Adverse Pregnancy Outcomes (HAPO) study upon which the new GDM diagnostic criteria are based. The prevalence of GDM may be underestimated by collecting specimens in unbuffered fluoride oxalate which is currently in widespread use by pathology practices for oral glucose tolerance testing. Pathology laboratories can play a vital role in the uniform implementation of clinical guidelines. It is essential that practical details such as terminology and specimen collection conditions are clearly defined in order to achieve uniform outcomes.