Data from: Cost effectiveness of the New Zealand Diabetes in Pregnancy guideline screening recommendations

Objective: To compare the cost effectiveness of two possible screening strategies for gestational diabetes from the perspective of the New Zealand health system, developed as part of a gestational diabetes guideline.
Design: A decision analytic model was built comparing 2-step screening (HbA1c at first booking and a 2 hour 75g OGTT as a single test at 24-28 weeks) with 3-step screening (HbA1c at first booking and a 1 hour GCT followed by a 2 hour 75g OGTT when indicated from 24-28 weeks) using a 9-month time horizon. Setting: A hypothetical cohort of 62,000 pregnant women in New Zealand. Methods: Probabilities, costs and benefits were derived from the literature and supplementary data was obtained from National Women’s Annual Clinical Reports. Main outcome measures: Screening and treatment costs (NZD$ 2013) and effect on health outcomes (incidence of complications). Results: The total cost for both strategies under baseline assumptions shows that the 2-step screening strategy would cost NZD$1.38m more than the 3-step screening strategy overall. The additional cost per case detected is NZD$12,460. The model found that the 2-step screening strategy identifies 12 more women with diabetes and 111 more women with GDM when compared against the 3-step screening strategy. We assessed the effect of changing the sensitivity and specificity of the OGTT. The baseline model assumed that the 2 hour 75g OGTT has a sensitivity and specificity of 95%. The 2-step strategy becomes more cost effective when the diagnostic accuracy measures are improved. Conclusion: Adopting a 2-step strategy would moderately increase the number of GDM cases detected at the same time as moderately increasing the number of women with false negatives at a significant cost to the health system. Further evidence on the benefits of the two different approaches would be welcome.