Gestational Diabetes During and After Pregnancy

3. Evolution of Screening and Diagnostic Criteria for GDM Worldwide

Mukesh Agarwal 

(1)

Department of Pathology, UAE University, 17666, Al Ain, United Arab Emirates

Mukesh Agarwal

Email: magarwal7@gmail.com

Abstract

The world’s preeminent diabetes and health organizations advocate a plethora of diverse algorithms for the screening and diagnosis of gestational diabetes mellitus (GDM). These criteria are followed by numerous countries globally. However, many countries formulate their own recommendations based on nationally derived regional data (e.g. Sweden). Furthermore, the obstetric, health, and endocrine associations within some countries support markedly dissimilar schemes for GDM (e.g. United Kingdom). Therefore, in most countries the screening and diagnosis of GDM is idiosyncratic. This disarray is independent of whether a country is affluent with outstanding health care (e.g. Canada) or is relatively poor without any influential diabetes society (e.g. Sri Lanka). This review examines the evolution of the guidelines advocated by some of these venerable international and national health organizations. It demonstrates how many of these recommendations for GDM were a) developed from tenuous data, b) often the result of expert-opinion only, c) sometimes economically driven, and d) frequently convenience-oriented. Our obstetric health care providers need one clear, objective, “evidence-based” global guideline. We contend that after decades of research, the light at the end of the tunnel for providing such a universal guideline for GDM does appear bright.

3.1 Introduction

Despite several international workshops and over four decades of research, there is still no unified global approach to GDM. Most countries have their own diabetes associations; the International Diabetes Federation (IDF) Web site lists 158 countries, each one with 1–3 diabetes societies as an IDF member.1 These societies often advocate guidelines for GDM, which may be similar or markedly different; often, no guideline is proposed. Most pre-eminent diabetes/health organizations like the American Diabetes Association (ADA),2 the Australasian Diabetes in Pregnancy Society (ADIPS),3 the Canadian Diabetes Association (CDA),4 the European Association for the Study of Diabetes (EASD),5 the New Zealand Society for the Study of Diabetes, and the World Health Organization (WHO)6 support screening for GDM. They offer comprehensive guidelines on how to screen, diagnose, treat, and follow-up women with GDM. Many other regional health associations, e.g., the National Institute for Health and the Clinical Excellence (NICE)7 from the United Kingdom and Clinical Resource Efficiency Support Team (CREST)8 from Northern Ireland also have guidelines for caregivers to follow. The scourge of GDM is the lack of an international consensus among these organizations.

In countries with guidelines derived from regional and national data (e.g., Japan, Australia, and Brazil), it would be reasonable to expect uniformity in the screening and diagnosis for GDM, at least within the jurisdiction of the health organization. However, there is a wide diversity in the methods used in most of these countries (e.g., the United Kingdom) due to multiple reasons. Health providers often prefer to use alternate criteria; they may choose to follow the recommendation of a diabetes or health organization from another country.9 Often there is disagreement between the country’s national diabetes organization, its local health society, and its regional obstetric organization, with each one recommending a different approach for GDM.

In countries without any nationally derived guidelines, the situation would be expected to be more disorderly. But this may not always be the case, as most of these countries have local diabetes organizations that may choose to implement 1 (e.g., Spain) or more of these “international” guidelines. The two most popular international guidelines are those of the WHO6 and the ADA.2 However, since both these organizations have changed their approach over the last three decades, some health providers (and/or their advising organizations) have not kept up with the latest changes and updates. Thus, although the practice in the United States has moved from O’Sullivan and Mahan’s criteria to the National Diabetes Data Group (NDDG-1979) to the Carpenter and Coustan (C&C) criteria for the diagnosis of GDM, both the NDDG and C&C may still be vogue in the same country/region/county. If more than one international guideline is approved by a national diabetes organization, the inconsistency between the various well-known health organizations (e.g., WHO vs. EASD) is reflected at the ground level within these countries. Thus, similar to countries with national data, the diversity in practice observed remains varied. There are additional problems in some of these countries; often, they have minimal testing for carbohydrate intolerance in pregnancy. A deficiency of resources and poor dissemination of information are some of the reasons for this shortcoming. Many countries in Africa, South America, and Asia suffer from this predicament.

This review is an attempt to get a bird’s eye-view of the reasons for dichotomy in the strategies for GDM, globally1011; it not an encyclopedic endeavor at synthesizing all the practices for GDM the world-over, which are easily available in multiple publications.12,13 An insight into the evolution of the common criteria for GDM diagnosis used worldwide may help us to find the ideal solution: one single, universal, global guideline for GDM.

3.2 Evolution of the World Health Organization Criteria

Outside of North America, the WHO criteria6 are the most uniformly accepted for the diagnosis of GDM, in part due to the global reach and influence of the WHO. The WHO guidelines were first published in 1965, one year after the first WHO Expert Committee on Diabetes Mellitus convened in Geneva. It was one of the earliest attempts at an international consensus on the classification of diabetes mellitus. At that time, GDM was defined as “hyperglycemia of diabetic levels occurring during pregnancy.” Subsequently, WHO guidelines evolved with bulletins in 1980, 1985, and 1999.

The WHO-1980 guidelines used the 75-g OGTT (for diabetes diagnosis in nonpregnant adults) limiting the requirement to only two (fasting and 2-hour (2-h)) plasma glucose levels, eliminating the need for intermediate readings. Pregnant women who met the WHO criteria for impaired glucose tolerance (IGT) in nonpregnant adults were classified as having GDM. The subsequent WHO-1985 criteria were very similar to the WHO-1980 criteria but for rounding the glucose values to the nearest tenth of a millimole instead of the nearest millimole. The WHO-1999 criteria (Table 3.1) incorporated some of the ADA-1997 recommendations, i.e., the fasting plasma glucose (FPG) was lowered (from 7.8 to 7.0 mmol/L) for the diagnosis of diabetes. However, the WHO has remained ambivalent about the term “impaired fasting glucose” (fasting glucose 5.6–6.9 mmol/L) of the ADA.

Table 3.1

Summary of major international recommendations for the screening and diagnosis of gestational diabetes

Continent

Organization

Screening

Screening method (1-h threshold ≥)

Diagnostic OGTT

Fasting

1-h

2-h

3-h

Abnormal values needed for diagnosis ≥

     

a = 50-g GCT (7.8)

b = 3-h, 100-g c = 2-h, 75-g

         

North America

ADA, 2003

NDDG, 1979

O’Sullivan and Mahan, 1964

CDA, 2003

SOGC, 2002

All except low-risk

No

All

Same as ADA

a

a

a

b

c

b

b

c

5.3

5.3

5.8

5.0

5.3

10.0

10.0

10.5

9.1

10.6

8.6

8.6

9.2

8.0

8.9

7.8

8.0

6.9

2

2

2

2

2

South America

BSD, 2007

All

FPG (4.7)

c

7.0

 

7.8

1

Europe

EASD, 1991

NS

NS

c

5.5 or 6.0

   

9.0

 

Asia

JDS, 2002

All

a

RPG (5.3)

c

5.5

10.0

8.3

2

Australia

ADIPS, 1998

NZSSD, 1998

All, unless resources limited

All should be offered

a

75-g (8.0)

a

75-g (8.0)

c

c

5.5

5.5

8.0

9.0

1

1

All continents (universal criteria)

WHO, 1999

ADA, 2003 (as above)

IDF, 2005

All except low risk

Glucose type NS

c

c

7.0

NS

NS

7.8

NS

1

ADA American Diabetes Organization; ADIPS The Australian Diabetes in Pregnancy Society; BSD Brazilian Society of Diabetes; CDA Canadian Diabetes Association; EASD European Association for the Study of Diabetes; IDFInternational Diabetes Federation; JDS Japan Diabetes Society; NDDG, National Diabetes Data Group; NZSSSD New Zealand Society for the Study of Diabetes; SOGC Society of Obstetricians and Gynecologists of Canada; WHOWorld Health Organization; NS not specified; FPG fasting plasma glucose; RPG random plasma glucose

Values given in mmol/L

Thus, the WHO has opted to apply the same criteria to the pregnant and nonpregnant state. The WHO criteria for GDM diagnosis were extrapolated to pregnant women from diagnostic cutoffs of the nonpregnant women. However, data from nonpregnant women and men may not be applicable to pregnant women.14 Conversely, the WHO criteria for GDM are relatively simple to use. Moreover, studies have shown that they predict both maternal and fetal abnormalities in index pregnancy15 as well as increased risk for type 2 diabetes after delivery.16

3.3 Evolution of the American Diabetes Association Criteria

Many countries outside North America use the ADA definition, which is unique in that it relies on the 3-h 100-g OGTT for the diagnosis of GDM. The original diagnostic glucose thresholds were first established by the pioneering studies of John O’Sullivan and Claire Mahan, in 1964.17 This study used the Nelson-Somogyi glucose assay, which was not specific for glucose, but measured all reducing substances present in whole blood. In 1979, the National Diabetes Data Group (NDDG)18 converted these whole blood glucose thresholds to the higher (approximately 14%) plasma glucose values, as most of the laboratory instruments by that time had started reporting plasma glucose values instead of whole blood glucose. In 1982, Carpenter and Coustan (C&C)19 modified the O’Sullivan and Mahan’s original glucose thresholds by using two conversion factors, which corrected for the nonglucose reducing substances in blood and converted whole blood glucose to plasma glucose. Therefore, these C&C thresholds are similar to the current “glucose specific” enzymatic methods measuring plasma glucose. The correction proposed by C&C has been validated.20 In 2000, the ADA endorsed the recommendations of the (1998) Fourth International Workshop-Conference on GDM21 proposal that until more data became available, the C&C thresholds be used for the interpretation of the 100-g, 3-h OGTT.

There have been criticisms of the ADA criteria. The current ADA criteria for the diagnosis of GDM (C&C) were derived from the original O’Sullivan and Mahan’s criteria for the 100-g OGTT, which were originally formulated to predict type 2 diabetes in the future and not to predict maternal and fetal problems in index pregnancy. However, many subsequent studies have substantiated that they can predict perinatal problems of pregnancy.15 Another criticism of the ADA criteria has been its application of the 100-g OGTT cutoffs to the 75-g OGTT plasma glucose values (Table 3.1).22

3.4 Evolution of the European Association for the Study of Diabetes Criteria

The Diabetic Pregnancy Study Group of the EASD was founded in 1969. Its recommendations for GDM were published in 1991.5 This report analyzed 1,009 pregnant women who underwent the 75-g OGTT in 11 centers across Europe. Glucose was analyzed on different samples i.e., venous whole blood/plasma or capillary whole blood or plasma. Approximately 10% of women exceeded the 2-h cutoff of 8.0 mmol/L (which was close to the WHO-1980 threshold of 7.8 mmol/L) for glucose intolerance. The authors concluded that the prevailing WHO criteria identified an excess of pregnant women of northern European origin with glucose intolerance. Therefore, they recommended that the definition of GDM be limited to women who reached glucose thresholds of diabetes, as defined by the WHO-1965 guidelines. For a diagnosis of “gestational IGT,” they proposed that the 2-h plasma glucose equal or exceed 9.0 mmol/L and either the fasting or the 1-h value exceed 7.0 and 11.0 mmol/L, respectively.

In 1996, the Pregnancy and Neonatal Care Group23 suggested the cutoffs of 6.0 mmol/L and 9.0 mmol/L be used for the fasting and 2-h plasma venous glucose, respectively (either one or both) (Table 3.1). These have been used as the EASD criteria for GDM.24 Studies have compared perinatal outcomes using WHO and EASD thresholds; however, no definite conclusions about the advantages of one set of criteria over the other could be made.25 Since the EASD glucose thresholds were derived from pregnant women (unlike the WHO), they are still popular in many centers in Europe.26 Nevertheless, despite new epidemiological data with the modern advances in glucose standardization and laboratory technology,27 the EASD recommendations have not changed in nearly two decades.

3.5 Evolution of The Australasian Diabetes in Pregnancy Society Criteria

The ADIPS first published its guidelines for GDM in 1998.3 Originally, its diagnostic criteria for GDM were adapted in 1991 from the WHO criteria for the 75-g OGTT.28 There has been much debate whether universal or selective screening is more appropriate for GDM diagnosis in Australian women. ADIPS recommends that screening should be considered in all pregnant women, i.e., universal screening. However, if resources are limited, screening may be reserved for those at highest risk. In other words, they endorse both selective and universal screening. The screening test recommended is either a nonfasting 50-g or 75-g challenge test with thresholds to proceed for the OGTT of ≥7.8 or 8.0 mmol/L, respectively. The suggested diagnostic thresholds for GDM on the 75-g OGTT are ≥5.5 mmol/L and ≥ 8.0 mmol/L (either one/both) for fasting and 2-h glucose, respectively (Table 3.1).

The criteria of ADIPS are the most liberal of all the diagnostic benchmarks for GDM in that they classify more women as having GDM than any other criteria.11 It has been suggested that one-third of women in Australia with type 2 diabetes could be identified earlier via a GDM pregnancy by the ADIPS diagnostic thresholds.29 Thus, they may be the ideal criteria for prevention of future type 2 diabetes, since they detect more women with carbohydrate intolerance.

3.6 Evolution of New Zealand Society for the Study of Diabetes Criteria

In New Zealand, the 1998 consensus guidelines of the ADIPS3 were accepted for the screening and diagnosis of GDM. However, by a majority decision of the New Zealand Society for the Study of Diabetes (NZSSD), the New Zealand criteria for GDM diagnosis were made more restrictive.3031 The 2-h cutoffs for the 75-g OGTT were raised to 9.0 mmol/L in New Zealand from the Australian 8.0 mmol/L threshold (Table 3.1) so that fewer women with GDM would be identified. The higher figure for the glucose threshold was also chosen “to reduce the worry and inconvenience for women of being given a false positive diagnosis and to reduce the strain on stretched specialist resources in many centers.” Community-based studies have shown that this would reduce the number of women with GDM by half thereby giving respite to New Zealand’s stretched resources.31 Thus, standards were dictated by resource use concerns and cost. The NZSSD recommendation is a little different from the Australian approach but very unlike the American College of Obstetricians and Gynecologists (ACOG) approach.32

3.7 Evolution of Japan Diabetes Society Criteria

The Japan Diabetes Society (JDS) has been a leader in diabetes screening in Japan. Over the last four decades, the JDS has changed its criteria for the diagnosis of diabetes in 1970, 1982, and 1995 in order to keep pace with the changes made by major international bodies. However, regarding GDM, the JDS currently continues to endorse the approach to GDM established in the early 1980s.33 These thresholds were established in 1984 by the Committee for Nutrition and Metabolism of the Japan Society of Obstetrics and Gynecology (JSOG). GDM is diagnosed when any two glucose values on the 75-g OGTT, exceeded 5.5, 10.0, and 8.3 mmol/L on the FPG, 1-h, and 2-h values respectively (Table 3.1). These cutoff values were initially selected from the mean value plus two standard deviations of healthy pregnancies. Later, their validity was also supported by greater frequency of abnormal perinatal outcomes in pregnant women. Subsequent studies have validated that these criteria as more predictive than the WHO criteria of pregnancy outcomes in Japanese women.34

After this initial report, some multicenter studies which investigated the screening of GDM in Japan became available. The accuracy and cost of various screening methods during the early and middle part of pregnancy were critically analyzed. In some of these reports, it was shown that in about 80% of Japanese women, GDM could be diagnosed during the first trimester of pregnancy. Further, it was also found that random blood glucose (threshold ≥5.5 mmol/L) and the glucose challenge test were valid screening methods.33

Thus, the JDS currently states that appropriate screening methods include a random blood glucose (cutoff : 5.3 mmol/L) in the first trimester and a glucose challenge test (cutoff: 7.8 mmol/L) in the second trimester. These recommendations differ from the findings of a study on screening tests for GDM in Japan.35 Currently, a Committee on the Reassessment of Definition, Screening, and Diagnostic Criteria for Gestational Diabetes Mellitus has been established under the aegis of the JDS. Based on new information from the Hyperglycemia and Pregnancy Outcomes Study (HAPO), a chapter on which is included in this book, the criteria are scheduled to be updated.

3.8 Evolution of Brazilian Society of Diabetes Criteria

The Brazilian Society of Diabetes (BSD) is one of the unique organizations that recommends using the fasting venous plasma glucose (FPG) as a screening test for GDM.36 An FPG of ≥4.7 mmol/L (at the first visit and at 24–28 weeks gestation) is used to decide if the diagnostic OGTT is needed. These recommendations are based on a study by the Brazilian Study of Gestational Diabetes (EBDG) Working Group published in 1998.37 However, the value of the FPG as a screening test in this study has been controversial, as shown by a review about the utility of the FPG as a screening test for GDM.38 The definitive diagnosis of GDM in Brazil is based on the criteria of the WHO-1999 for the 75-g OGTT (Table 3.1). The BSD submits that most of the current recommendations for GDM are based on consensus of specialists which should be replaced by recommendations based on evidence.36

3.9 International Diabetes Federation Guidelines

The International Diabetes Federation (IDF)39 acknowledges that there are no randomized control trials testing the effectiveness of GDM screening. It also notes that there are many strategies available. Its 2005 recommendations are a hybrid of the ADA and WHO guidelines. Screening in low-risk women should be done by a plasma glucose (fasting, random, or postprandial not specified) at the time of the first antenatal visit or directly with a 75-g OGTT in women at high-risk for GDM (criteria not defined).

3.10 Regional Approaches to GDM

In this section, the actual screening practices in some selected countries and continents are outlined. In almost all countries without exception, there is a wide spectrum of practices for the screening and diagnosis of GDM.

3.10.1 Canada

In Canada, a decision not to screen, to screen all pregnant women, or to screen only women at “high-risk” would all be acceptable approaches based on the current recommendations. The two main associations that have published guidelines for GDM are the CDA4 and the Society of the Obstetricians and Gynecologists of Canada (SOGC).40 Both organizations have updated GDM guidelines over time based on available data. However, they differ considerably (Table 3.1). The SOGC-2002 recommends a scheme which is similar to that of the ADA i.e., selective screening with a 50-g GCT followed by a 100-g OGTT or 75-g OGTT, using the ADA criteria for diagnosis. However, the SOGC also agrees that not screening for GDM is also considered acceptable. The CDA prefers universal screening, due to the risk of missing cases with selective screening with a 50-g GCT.4 However the diagnosis is based on the 75-g OGTT with much tighter thresholds than the ADA criteria; in fact the CDA criteria have some of the most stringent thresholds for the 75-g OGTT.11

The problem of a lack of consensus in Canada illustrates the challenges of GDM globally, if extended into a wider context. Consider a woman living in a Canadian province, who does not have GDM based on the 75-g OGTT by the CDA criteria. If she moves to another district in Canada, she will now have GDM if the SOGC recommendations are in vogue. A similar situation would also arise if she crosses the border into the USA, where the more liberal ADA criteria are used. The reverse would be true if she moved in the opposite direction. This lack of consensus is well summed up by the CDA: “In the year 2003, screening, diagnosis and management of GDM remain controversial and continue to be debated in the medical community.4

3.10.2 United Kingdom

The National Institute for Health and Clinical Excellence (NICE) guidelines of March 2008 recommend that the random and fasting glucose, GCT, or urinalysis should not be used for screening of GDM. Rather, screening should be done using risk factors followed by a 75-g OGTT using the criteria of WHO-1999 for the diagnosis of GDM.7

The Scottish Intercollegiate Guidelines network (SIGN) advocates recommendations contrary to NICE for both the screening and diagnosis of GDM. Its latest guidelines (2001) propose the use of glucosouria and random venous glucose for screening, with the 75-g OGTT and the EASD criteria used for diagnosis.41

The CREST Working Group on Diabetes in Pregnancy guidelines were developed for Northern Ireland in 2001.8 Guidelines recommend a diagnostic 75-g OGTT if (a) urine shows glycosuria, (b) fasting glucose or 2-h glucose levels after food exceed 5.5 mmol/L, or (c) plasma glucose within 2-h after food exceeds 7.0 mmol/L. They recommend diagnostic thresholds from the EASD-1991 study, i.e., either FPG ≥5.5 mmol/L or 2-h ≥9.0 mmol/L.

Not surprisingly, surveys in the U.K. have shown that there is wide variation in the practices for screening and diagnosis of GDM. In a recent mail-questionnaire study,42 the screening practices among the respondents was variable and included glycosuria (40%), random venous glucose (28%), and FPG (6%). The confirmatory test was the 75-g OGTT, but the thresholds for diagnosis varied considerably. Two other studies have shown similar variation in the approach to GDM among the various caregivers/obstetric units in the U.K.43,44

3.10.3 Italy

The Italian Treatment Standards for Diabetes were drafted in 2007 by members from several Italian associations including the Italian scientific diabetes societies, Italian Society of Diabetology (SID), and the Italian Association of Diabetologists (AMD).45 The guideline was formulated after considering all the major international recommendations for GDM, including the suggestions of the Italian Society of Obstetrics and Gynecology (SIGO). They have endorsed the latest approach of the ADA (the C&C thresholds for the 75-g OGTT) but are waiting for the results of the HAPO to make further recommendations.

A survey from Italy46 has shown that only 50% of the laboratories performed the OGTT as per the protocols of their diabetes association. There was a wide variability in the OGTT used after a positive GCT. Some laboratories performed the 100-g OGTT, others the 75-g OGTT with 2–4 blood samples for diagnosis; many laboratories used only the 50-g GCT without confirmation by a follow-up OGTT. Some Italian laboratories used a variety of unique methods. A variable relationship between laboratories and diabetes organizations was detected, leading to the conclusion that there was a need for greater collaboration between the different regulatory bodies.

3.10.4 Australia

In Australia, despite the presence of ADIPS, an audit of 360 hospitals across the country47 showed that the 50-g GCT was the most popular screening test, but 10% hospitals still used either a random glucose or a 75-g OGTT for screening. For the diagnosis for GDM, 30 (12%) hospitals used the obsolete 50-g OGTT, while 2% used the 100-g OGTT, which is not recommended by ADIPS.3 Moreover, the number of glucose samples used to confirm a diagnosis varied from 1 to 3 values on the diagnostic OGTT.

3.10.5 Sweden

In Sweden, similar to many other countries, both the screening and diagnostic criteria for GDM have changed over time. In the early 1980s, screening for GDM was done by urine glucose. Subsequently, random blood glucose with a cutoff of 6.1 or 5.6 mmol/L for less or more than 2-h after a meal was used.48 Later in 1985, repeated random blood glucose measurements became popular, with a cutoff of over 6.5 mmol/L as the threshold for proceeding to the OGTT.49 In 1991, the popular Hemocue apparatus, which uses 5 μL of capillary whole blood (Hemocue AB, Angleholm, Sweden), was introduced into the Swedish market. Since then, most studies from Sweden have used capillary whole blood. In fact, even for the diagnostic OGTT, capillary whole blood is more likely to be used all over Sweden rather than plasma glucose. Currently, many large centers use 4–6 capillary glucose measurements as screening tests starting from the end of the first trimester with a value of ≥8.0 mmol/L as the threshold to proceed with the diagnostic OGTT.50

Regarding diagnosis, most Swedish units used the WHO-1985 diabetes criteria for capillary whole blood with either fasting ≥6.7 mmol/L or 2-h values ≥11.1 mmol/L after a 75-g OGTT. After the publication of the EASD study in 1991, a 2-h IGT value of 9.0–11.0 mmol/L was used for the diagnosis of GDM. With some exceptions, these criteria have been generally accepted in Sweden since the early 1990s, similar to many European countries. However, even as late as 2001 many counties (around Stockholm and Orebo) were using the WHO-1965 criteria for GDM, which did not consider “IGT in pregnancy”51as GDM. This was different from most of Sweden which included “IGT in pregnancy” as diagnostic for GDM. Thus in Sweden, there is heterogeneity in the diagnosis of GDM; additionally, using capillary whole blood extrapolated from values for plasma remains an additional complicating factor.52

3.10.6 Germany

There have been many discussions about the screening and diagnosis of GDM in Germany. In 2001, the guidelines were based on the suggestions of an expert panel of the German Society of Obstetrics and Gynecology (DGGG) and the German Diabetes Association (DDG). These were modified recommendations of the Fourth International Workshop-Conference on GDM. Women are screened on the basis of risk factors in the first trimester. Both the one-step (75-g OGTT alone) and the 2-step approach (50-g GCT followed by a 75-g OGTT) are accepted as valid methods for screening and diagnosis of GDM. The threshold for the GCT is a glucose value ≥ 7.8 mmol/L. Some of the diagnostic cutoffs for the 75-g OGTT have been retained from the original data of O’Sullivan and Mahan (1964), i.e., fasting,1-h, and 2-h thresholds are 5.0, 10.0 and 8.6 mmol/L, respectively.53 The possible reason is that in many parts of Germany, capillary whole blood was still being used for measuring glucose; formerly, the Hemocue was the only glucose meter approved by the German Diabetes Association for point-of-care testing.

3.10.7 China

In China, there is no consensus on which criteria are best suited for Chinese women; therefore, most hospitals have adopted one of the criteria of the various international organizations. In 1993, Dong Zhiguang suggested Chinese-specific criteria for the 75-g OGTT. They were lower than WHO criteria but similar to the criteria of the JDS. These criteria have been popular in China. However, it has also been shown that criteria of Carpenter and Couston as applied to the 100-g OGTT are suitable for Chinese women.54 A chapter on diagnostic testing in China is included in this book.

3.10.8 South America, Africa, and Asia

There is a paucity of data about diabetes from many countries of these continents. Even lesser data is available about the practices regarding the screening and diagnosis of GDM. Hence, the methods used are harder to gauge in these regions. In South America, Brazil and Argentina are on the forefront of research on GDM.3755 Publications from Uruguay show that they follow the thresholds suggested by the NDDG. There is little information from Peru, Bolivia, Chile, and Venezuela. The African continent exhibits the same issues as South America, in that there is a lack of published data on OGTT reports. Studies from Ethiopia, Nigeria, Uganda, and South Africa show that the WHO criteria are popular.5659

In some countries of Asia, like Korea,60 Sri Lanka,61 and Malaysia,62 the WHO-1999 criteria appear to be used most frequently. However, other countries like Thailand63 and Turkey64 use the 50-g GCT followed by the 100-g OGTT as recommended by the ADA. In India6566 and the Middle-East,11 both ADA and WHO criteria are frequently used. In Hong Kong, selective screening is popular67; additionally, the WHO criteria have been validated in pregnant Chinese women from Hong Kong.68

3.11 Conclusions

The evolution of the screening and diagnostic criteria for GDM worldwide have been in flux. As can be appreciated from this review, guidelines may lack updates and they often rely on expert opinion rather than evidence based data. We can best serve the interest of our pregnant patients by formulating unified universal guidelines for GDM133069; this consistency is essential for GDM. In many other areas of medicine, such standardization in clinical research has been attained with fruitful results.70 Consensus could be achieved due to the insight gained from the recent trials; an awareness of the shortcomings of the various global guidelines would help to avoid them in the future. With over four decades of hindsight, it is high time that we develop one clear-cut global guideline for GDM.

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