STUDY IMPLICATIONS

6.4.1 Implications for practice

The systematic review has analysed and drawn conclusions based on existing evidence in the field. Universal screening is recommended for countries or areas wherein GDM prevalence is relatively high and economic constraints are not experienced. For areas where GDM prevalence is low, it is recommended that they retain their current practice (whether it is universal or selective screening) before more robust evidence emerges. For countries which are implementing selective screening, a risk score-based selective screening approach could be explored. For the risk score calculation in real practice during future implementation, it is easy for practitioners to make calculations when they are facilitated by a simple web- or computer-based calculation tool. A similar tool is the QRISK2 tool for cardiovascular risk calculation (https://www.qrisk.org/2016/).

Pregnant women generally believe that the IADPSG one-step screening approach is important and necessary to be carried out on all expectant mothers. However, the non-GDM women feel strongly that the OGTT test is inconvenient and a burden. Also both the GDM and non-GDM participants felt that they would like more information both before and after the OGTT. In GDM screening services, it is recommended that a detailed GDM and OGTT information leaflet should be offered to pregnant women both before and after the OGTT to meet their health needs.

Translating the research evidence to real-world guidelines, policymaking and implementation can be challenging and time-consuming. While a great deal of research evidence exists, relatively little has been disseminated, taken up or applied in practice. Currently, as described in the Chapter 1, substantial inconsistencies and

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controversies exist between research evidence, guidelines and different field practices for gestational diabetes screening. The research evidence is of little relevance if it remains unused by health clinicians and policymakers.

However, policymaking or guideline setting is a process of deliberation. Apart from scientific evidence, other factors such as values and the culture of each country can be influential. Countries have different values in relation to effectiveness and cost- effectiveness, which are sometimes associated with, but not always relevant to, the economic level of the country. For example, cost-effectiveness of heath care is emphasised in the UK (Raspe, 2016), which might be one of the reasons for implementation of selective screening in the UK as suggested by NICE (2015). Secondly, different countries have different normative cultures in healthcare. For example, Sweden and Norway have person-centred solidarity, whereas the UK has community-centred solidarity (Raspe, 2016). The UK tends to care more about health maximisation as a whole, compared to the person-centred solidarity, which tends to prioritise the worst off or sickest. Under such cultural imperatives, the UK presents a large chance to balance the benefit of avoiding unnecessary OGTT/burden for non-GDM women (over 90% of all pregnant women) and the cost of missing a small proportion of GDM women. Thirdly, understanding patient needs and promoting patient involvement in healthcare decision making is being increasingly emphasised and implemented. Therefore, it is considered of value to provide space for the projection of patients’ voices when making any healthcare decision including GDM screening.

6.4.2 Recommendations for future research

The systematic review identified only one cost-effectiveness study on universal versus selective screening for GDM (Poncet et al., 2002). This showed a slight

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difference between, indicating that the cost to obtain one unit of additional effectiveness under universal screening was 1.1 times more expensive than that for selective screening. More cost-effectiveness studies will be needed to advance more robust conclusions.

There are only three existing studies on a risk score-based selective screening approach for GDM, each demonstrating that developing a risk-scoring algorithm based on the local population profile made selective screening an effective screening approach. However, more risk score studies are recommended for each country. The effectiveness of the risk score-based selective screening approach is high dependent on the local setting of each country. When conducting future risk-score studies, it is essential that the researchers should investigate a full range of potential GDM risk factors to maximise the accuracy and effectiveness of the prediction model, since it is uncertain whether any other simple biomarkers can improve upon this prediction. A recent study (Meek et al., 2016) showed how even random glucose is a better predictor of GDM than BMI or maternal age during the first trimester. Some recent studies showed that the homeostatic model assessment for insulin resistance index (HOMA IR) level was associated with GDM and could be used as a predictor (Mohamed et al., 2013; Alptekin et al., 2016). Whether these hold true in Chinese population is a matter of research in the future. Additionally, it also remains to be established whether the random glucose indicator could be improved by using HbA1c as a predictor, either on its own or as a composite risk marker. Whether any urinary metabolomics during 1st trimester could be used as predictor for GDM worth further investigation. In the study of Sachse et al. (2012), an increase of excreted urinary citrate correlated with the severity of GDM was observed. Meta-analysis of candidate gene studies and genome-wide association analysis (GWAS) have identified a number of genes which were reproducibly associated with GDM, including TCF7L2, GCK, KCNJ11, KCNQ1, CDKAL1, IGF2BP2, MTNR1B, and

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IRS1 (Lowe et al., 2016). These genes are also associated with T2DM. Genetics of T2DM and GDM as predictive markers of GDM are also worth exploring in the future.

Since only two studies on pregnant women’s perspectives on GDM screening have been conducted in Australia (Griffiths et al., 1993) and China, with the Australian study being conducted early in 1993, future qualitative perspective studies are needed under other local screening settings other than China. This is to ensure that patient needs and viewpoints are understood fully so as to facilitate decisionmaking for each country.

There is trend to transfer the outcome measure of test accuracy to clinical outcomes for screening studies. The systematic review synthesised the test accuracy of selective screening in comparison with universal screening. As explained in the Discussion section in Chapter 3, the present systematic review did not synthesise clinical outcomes is because there were only three studies (Griffin et al., 2000; Cosson et al., 2006; Ezimokhai et al., 2006) using the clinical outcome measures but each had the same bias in study design. The most appropriate study design compares the clinical outcomes of all pregnant women not just GDM women under the two screening approaches. Therefore, it is recommended that future studies are designed in line with this consideration. Moreover, future studies can also examine the clinical outcomes of the GDM women with lowest risk. These are the GDM women who would be missed during the application of selective screening as having none or low risks; whether or not these lowest risk GDM women develop adverse outcomes has important implications for assessing the selective screening approach. As a further step beyond using clinical outcome measures, future studies could consider using a decision tree to illustrate the two choices of universal screening and selective screening approaches. A decision tree is a decision support tool that uses a tree-like

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graph or model of decisions and their possible consequences, including chance event outcomes, resource costs, and utility. Use of this technique can further facilitate the judgment and decision making in clinical medicine.