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 Table of Contents  
Year : 2013  |  Volume : 5  |  Issue : 3  |  Page : 191-194

New guidelines for diagnosis of gestational diabetes: Pathology-based impact assessment

1 Charles Darwin University, NT; NSW Health Pathology, NSW, Australia
2 Charles Sturt University, NSW, Australia
3 NSW Health Pathology, NSW, Australia

Date of Web Publication20-Mar-2013

Correspondence Address:
Ezekiel Uba Nwose
School of Psychological and Clinical Sciences, Casuarina Campus, Yellow 2.2.58, Charles Darwin University, NT 0909
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Source of Support: Management of South West Pathology Service of NSW Health Australia., Conflict of Interest: None

DOI: 10.4103/1947-2714.109184

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Background: A recent study indicated an average of 19.5% abnormal oral glucose tolerance in antenatal clients per year. Aim: The purpose of this study was to determine the impact on gestational diabetes cases due to new guidelines for diagnosis and classification of hyperglycaemia in pregnancy. Materials and Methods: This study reviewed the archived clinical pathology data on oral glucose tolerance tests performed between January 1999 and December 2008 on antenatal clients ( N = 615). The cases were reviewed to determine changes if any in percentage of gestational diabetes due to new guidelines. Results: Over the 10 years period, a yearly average of additional 10.8% antenatal cases suggestive of gestational diabetes was observed due to the new recommended thresholds. Further, the average yearly incidence would have increased from 8.8 cases to 16.2 cases, which translates to almost 46% increase in the prospective numbers of gestational diabetes. Conclusions: This report presents the extent of how the new recommended guidelines for diagnosis and classification of hyperglycaemia in pregnancy could increase the prevalence of gestational diabetes. It also provides pathology-based evidence for the epidemiology of gestational diabetes mellitus and allows for planning the costs that would be attendant to the full implementation of the new guidelines.

Keywords: Gestational diabetes, Impact evaluation, New guidelines, Oral glucose tolerance test, Pathology-based evidence

How to cite this article:
Nwose EU, Richards RS, Bwititi PT, Butkowski EG. New guidelines for diagnosis of gestational diabetes: Pathology-based impact assessment. North Am J Med Sci 2013;5:191-4

How to cite this URL:
Nwose EU, Richards RS, Bwititi PT, Butkowski EG. New guidelines for diagnosis of gestational diabetes: Pathology-based impact assessment. North Am J Med Sci [serial online] 2013 [cited 2023 Jun 7];5:191-4. Available from: https://www.najms.org/text.asp?2013/5/3/191/109184

  Introduction Top

A report from Norway published in 1994 in the Scandinavian Journal of Primary Health Care indicated a prevalence of up to 45% abnormal oral glucose tolerance test (OGTT). [1] Although OGTT is highly criticized as inconsistent, inconvenient and poorly reproducible, [2] it still adds predictive advantage to the use of fasting blood glucose level alone. Thus, it is still the gold standard, [2],[3] especially to make gestational diabetes diagnoses. However, 18 years since the Norwegians' report, corroborative data from other countries are lacking, including pathology-based evidence regarding the actual prevalence of gestational diabetes.

In 2010, the International Association of Diabetes and Pregnancy Study Groups issued new guidelines for diagnosis and classification of hyperglycaemia in pregnancy. That is, diagnosis of gestation diabetes mellitus (GDM), which is defined in this report as any degree of glucose intolerance with onset or first recognition during pregnancy. [4] A concern is that there is a subpopulation of overt diabetics in antenatal patients who are at risk of adverse pregnancy outcomes, but there seems to be no clear correlation to hyperglycaemia. [4],[5] Thus, the new guidelines introduced a brand set of thresholds and recommendations. Since the recommendations, there have been series of comments, [5],[6],[7],[8],[9] especially on the potential increase in number and the associated cost of management of gestational diabetes. [10],[11],[12] However, pathology-based data indicating the extent of the increase is yet to be reported. Such a study would be a contribution to the epidemiology on the impact of the new guidelines in terms of quantity of laboratory reports of abnormal OGTT suggestive of gestational diabetes.

  Materials and Methods Top

Study setting

This work was done at the South West Pathology Service of New South Wales (NSW) Health Australia, as part of a Translational Biomedical Science Research initiative. The pathology operates a Laboratory Information System (LIS) that could only be access by permission and with a password. The Ethics Committee of the Area Health Service approved the acquisition and use of de-identified database from the LIS. The database comprises 10 years of archived clinical pathology data from January 1999 to December 2008. All OGTT (glucose load 75 g) performed in the 10 years period were audited. This included 5126 cases, of which 615 were antenatal. The OGTT results from the 10 years under review, including all those selected as GDM, had blood glucose levels for the three points (fasting, as well as 1 h and 2 h postprandial).

Source of information and definition on gestational diabetes

As this study was based on de-identified data, and no immediate benefit for the study clients was envisaged, no personal contact was made or letter from clinicians solicited ( N = 615). OGTT were performed on antenatal patients. There was no record indicating previous diabetes or pre-diabetes on these clients. The source of information about GDM for this evaluation was from the de-identified OGTT reports in the LIS. The definition of GDM was based on the clinical pathology reports sent out to the clinicians, i.e. cases that were reported as indicating gestational diabetes were evaluated as percentage of the 615 antenatal subpopulations.


To assess the impact of the new guidelines on potential increase in number of GDM, the same antenatal subpopulation ( N = 615) was further reviewed. Based on the recommended threshold, data were sorted as follows:

  1. First, by the diagnostic report sent to clinicians: for each year, those reported as suggestive of GDM were ranked on top. The counts were evaluated as percentage of antenatal subpopulations to determine the prevalence of GDM diagnosis (% Dx).
  2. Second, by the new threshold: those not reported as suggestive of GDM, but had fasting blood glucose level of 5.1 mmol/L (92 mg/dL), 1-h postprandial glucose level of 10.0 mmol/L (180 mg/dL) and/or a 2-h postprandial glucose level of 8.5 mmol/L (153 mg/dL) were identified. [4] The counts were evaluated as percentage of antenatal subpopulations to determine the prevalence of "DM diagnosis based on new guideline" (% other).
  3. The absolute numbers that made up "% Dx" and "% other," from (i) and (ii), respectively, were then pooled together to determine the might-have-been prevalence or prospective GDM diagnosis (% Pro) by the new guidelines. Lastly, the fraction of the "other" in the "Pro" for the 10 years period is expressed as the potential impact of the new guidelines.

  Results Top

The summary statistics of the results is presented in table. The yearly average of 19.5% was reported as gestational diabetes [Table 1]. The focus of evaluations is the "normal" reports; how many of them would have been reported as GDM based on the new recommended guideline or threshold. Using the new guidelines, the results show an additional yearly average of 10.8%, and the 10 years additive of 12% (74 out of 615) would have been reported as GDM. That is, the incidence or number of GDM cases would have increased from 88 to 162 [Table 2], which translates to approximately 46% impact [Figure 1].
Figure 1: Percentage* impact of the new guidelines on number of gestation diabetes mellitus cases

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Table 1: Summary statistics of all oral glucose tolerance test reports for antenatal subpopulation

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Table 2: Yearly incidence of gestation diabetes mellitus cases with and without considering the new guidelines

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  Discussion Top

The main focus of this study was to investigate and quantify the potential impact of the new guideline thresholds for diagnosis or classification of hyperglycemia in pregnancy. Initial review shows that by the pathology's protocol, yearly average of 19.5% of antenatal OGTT tests were reported as gestational diabetes. [13] A further review of the case reports that were classified as normal [Table 1], but this time using the new recommended thresholds, revealed that an additional yearly average of 10.8% would have been reported as gestational diabetes [Table 2].

A cursory look at the descriptive statistics or the information on [Table 2] may not reveal the full impact of the new recommendations on prospective incidence of GDM. For instance, it could be hastily translated to be "10.8/(19.5 + 10.8) ×100 = 35.6%." Another potential hasty translation could be to take only 1 or 2 years, but the results show unevenness in the yearly impact. A critical evaluation shows that the increase in number from 88 to 162 translates to 45.7% [Figure 1].

It is pertinent to note one of the reviews of the new criteria that the total incidence of gestational diabetes in the Hyperglycemia and Adverse Pregnancy Outcome (HAPO) population was 17. 8%, [7] which is less than half of what is being reported here. This is probably a reflection of the different populations studied. Nevertheless, the significance comes to bear in estimating and planning for the management of GDM in the population, and reinforces the call to study local populations because of geographical and social impacts among others.

  Conclusion Top

We report a level of prevalence of abnormal OGTT that has yet to be fully appreciated. We also report pathology-based evidence that the new guidelines for diagnosis and classification of hyperglycaemia could increase the GDM cases by as much as 46%. The importance of this report is in the epidemiological information necessary for estimating the cost of adopting criteria.

  Acknowledgments Top

The acquisition of archived clinical pathology data used in this work was permitted and supported by the management of South West Pathology Service of NSW Health Australia. There is no financial interest.

  References Top

1.Rutle O, Bruusgaard D, Furuseth K, Vaaler S. Oral glucose tolerance test in general practice - When is it worthwhile? Scand J Prim Health Care 1994;12:255-60.  Back to cited text no. 1
2.Waugh N, Scotland G, McNamee P, Gillett M, Brennan A, Goyder E, et al. Screening for type 2 diabetes: Literature review and economic modelling. Health Technol Assess 2007;11:3-iv, ix-xi, 1-125.  Back to cited text no. 2
3.Sorkin JD, Muller DC, Fleg JL, Andres R. The relation of fasting and 2-h postchallenge plasma glucose concentrations to mortality: Data from the Baltimore Longitudinal Study of Aging with a critical review of the literature. Diabetes Care 2005;28:2626-32.  Back to cited text no. 3
4.International Association of Diabetes and Pregnancy Study Groups Consensus Panel, Metzger BE, Gabbe SG, Persson B, Buchanan TA, Catalano PA, et al.; International association of diabetes and pregnancy study groups recommendations on the diagnosis and classification of hyperglycemia in pregnancy. Diabetes Care 2010;33:676-82.  Back to cited text no. 4
5.Mandelbrot L, Legardeur H, Girard G. Screening for gestational diabetes mellitus: Is it time to revise the recommendations?. Gynecol Obstet Fertil 2010;38:409-14.  Back to cited text no. 5
6.Mulla WR, Henry TQ, Homko CJ. Gestational diabetes screening after HAPO: Has anything changed? Curr Diab Rep 2010;10:224-8.  Back to cited text no. 6
7.Legardeur H, Girard G, Mandelbrot L. Screening of gestational diabetes mellitus: A new consensus?. Gynecol Obstet Fertil 2011;39:174-9.  Back to cited text no. 7
8.Weinert LS. International Association of Diabetes and Pregnancy Study Groups recommendations on the diagnosis and classification of hyperglycemia in pregnancy: Comment to the International Association of Diabetes and Pregnancy Study Groups Consensus Panel. Diabetes Care 2010;33:e97; author reply e98.  Back to cited text no. 8
9.Hadar E, Hod M. Establishing consensus criteria for the diagnosis of diabetes in pregnancy following the HAPO study. Ann N Y Acad Sci 2010;1205:88-93.  Back to cited text no. 9
10.Werner EF, Pettker CM, Zuckerwise L, Reel M, Funai EF, Henderson J, et al. Screening for gestational diabetes mellitus: Are the criteria proposed by the international association of the Diabetes and Pregnancy Study Groups cost-effective? Diabetes Care 2012;35:529-35.  Back to cited text no. 10
11.Reece EA, Moore T. The diagnostic criteria for gestational diabetes: To change or not to change? Am J Obstet Gynecol 2012 [In press].  Back to cited text no. 11
12.Cundy T. Proposed new diagnostic criteria for gestational diabetes - A pause for thought? Diabet Med 2012;29:176-80.  Back to cited text no. 12
13.Nwose EU, Richards RS, Cann NC. Prevalence of abnormal oral glucose tolerance with concomitant dyslipidaemia: Implications for cardiovascular risk assessment in prediabetes. Br J Biomed Sci 2012;69:97-8.  Back to cited text no. 13


  [Figure 1]

  [Table 1], [Table 2]

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