Fase 2: Cálculo del potencial turístico de los recursos arquitectónicos

The decision to adopt the IADPSG criteria globally and in particular in SA has been contentious for several reasons.

1. Firstly the IADPSG is associated with significantly increased prevalence. The expected increase is to up to 17.8% varying across populations between 9.3-25% (22). This is thought to be secondary to the lowering of the FPG cut off in those countries where the WHO-1999 criteria is used and to the lack of the initial 50 g glucose challenge in regions using the Carpenter-Coustan criteria. In countries like India where the previous WHO criteria and the 2 step Carpenter and Coustan [79] criteria are prevalent, the impact of changing to IADPSG may be significant. Studies have reported upto a three times increase in the prevalence of GDM by the IADPSG criteria in Asians[80].

2. Secondly, without including SA in the HAPO study it is impossible to say whether the odds of LGA in SA are comparable to WC at a particular glycaemic level. Considering that the prevalence of LGA in SA is far lower than WC, the corresponding level of glycaemia to result in the odds ratio (OR) of LGA of 1.75 could in fact be higher. Also, it has been shown that the effect of glycaemia on birth weight varies with ethnic groups [18, 81]. One recent study that compared the effect of the IADPSG criteria on a large population including SA minority in fact recommended lower GDM diagnostic thresholds for SA than in WC[82].

3. Thirdly, there is evidence from the DECODE study that SA have a greater proportion 2hPG abnormalities compared to FPG abnormalities and it is possible that raising the 2hPG cut off might miss a significant proportion of

the SA minority group [83]. In the HAPO study 55% of women were diagnosed based on FPG alone, however this was as low as 24-26% in Bangkok and Hong Kong, and up to 47% in Singapore reflecting ethnic differences in the prevalence of fasting and post-prandial hyperglycaemia. The highest rates of diagnosis by FPG were in Barbados and America (74 and 73%). Although lowering the FPG cut off to 5.1 is expected to identify women who are likely to be missed by the increased 2hPG cut off of 8.5mmol/l, this has not been assessed systematically in mixed ethnic populations.

4. Fourthly, it is now increasingly recognised that maternal obesity is a more significant and independent player for LGA and C-Section rates than maternal glucose except at the highest glucose category [71, 84, 85]. In fact 75% of LGA in the HAPO study were born to mothers without with normal glucose tolerance. The long-term risks of obesity and glucose intolerance in offspring associated with GDM were lost when maternal BMI is factored into the analysis [86]. With significantly lower prevalence of obesity in SA, it is conceivable that the OR of foetal outcome, especially LGA in the different glycaemic categories would be very different.

5. Lastly, evidence of treatment benefit in this newly diagnosed additional population with mild fasting hyperglycaemia is lacking. Two intervention studies, the ACHOIS and MFMU trials published in 2005 and 2009 showed the benefit of treating mild GDM, using 75g OGTT [10] and 100g OGTT [11] respectively. It is important to note that neither of these intervention studies included the same outcomes used to define the IADPSG criteria as their composite primary outcome, except the C-peptide level in the MFMU

43 study [11]. The ACHOIS trial screened women using either risk factor based selective screening or 50g glucose challenge test (GCT) to select women with a 1hPG ≥ 7.8mmol/l for the 75g OGTT. They defined mild GDM as FPG <7.8mmol/L with 2hPG between 7.8 & 11.1mmol/l on 75g OGTT. 95% of women in the ACHOIS study had a fasting plasma glucose (FPG) levels between 3.4mmol to 6.2mmol, with median (IQR) 2-hour glucose value of 8.6 (8.1-9.3) mmol/l after a 75g OGTT [10]. The MFMU trial used an initial screening test of 50g GCT to select women with 1hPG between 7.5 and 11.1mmol/l to undergo a subsequent 100g OGTT. Mild GDM was defined as FPG<5.3mmol/l with one of 3 other thresholds that include 1hPG, 2hPG, and 3hPG values greater than 10.0, 8.6 and 7.8mmol/l respectively. In the MFMU trial 95% of the women in the intervention arm had a FPG between 4.5 and 5.1mmol/l with a 2-hour value ranging between 7.2 and 12.1mmol/l after a 100g OGTT [11]. Therefore, while there was some overlap in the glycaemic ranges with the proposed IADPSG criteria in both these trials, a direct extrapolation of the results from the available interventional studies is difficult given the differences in screening methods and selection criteria used. Again both these trials were conducted in a predominantly WC population.

With both the NICE and IADPSG criteria recommending lower FPG thresholds than the prevalent mWHO99 criteria there is increased pressure among care providers to adopt a change in practice [87]. If universal screening is followed, the incidence of GDM is expected to increase to up to 17.8% with the new IADPSG criteria [88], identifying a larger proportion of women with mild fasting glucose abnormalities. However, many countries and around 90% of the units in the UK still use risk factor

based selective screening, with a majority using the WHO / mWHO-99 criteria for diagnosis with a 75g OGTT [89]. Only 4% of UK centres adopted the IADPSG criteria [89].

Meek et al were the first to compare the likely impact of the NICE and IADPSG criteria in a retrospective cohort. The centre used a random blood glucose in early pregnancy, and subsequent glucose challenge test (GCT) at 26-28 weeks for screening followed by a diagnostic 75gOGTT at 26-28 weeks [90]. They reported the highest risk of LGA and CS in the group diagnosed by IADPSG and NICE criteria compared to control women who did not have OGTT. While this study added additional critical evidence for the diagnosis of GDM, this may not be applicable to the UK and other countries that follow risk factor based selective screening and not a GCT. The impact of the new NICE guidelines should ideally be studied on a selectively screened population, on which the evidence for the guideline is largely based.

45