Cost effectiveness of early metformin in addition to usual care in the reduction of gestational diabetes mellitus effects (EMERGE)-A randomised placebo-controlled clinical trial.

Aims: To investigate the cost-effectiveness of early initiation of metformin and usual care for gestational diabetes mellitus (GDM).

Methods: Economic evaluation from a healthcare perspective, based on the EMERGE randomised controlled trial. In total, 535 women with GDM were randomised to placebo in addition to usual care or metformin in addition to usual care. Economic outcomes included incremental healthcare costs and quality adjusted life years (QALYs) and expected cost-effectiveness at cost-effectiveness threshold values of €20,000, €45,000 and €100,000 per QALY gained. Uncertainty was explored using parametric, non-parametric, deterministic and probabilistic methods and heterogeneity using subgroup analysis.

Results: On average, relative to the placebo arm, the early metformin arm was associated with non-statistically significant mean increases of €193.07 (95% CI: -€789.88, €1176.01; p = 0.700) and 0.002 QALYs (95% CI: -0.009, 0.013; p = 0.771). In terms of expected cost-effectiveness at threshold values of €20,000, €45,000 and €100,000 per QALY gained, the probability of the early metformin arm being more cost-effective was estimated at 0.423, 0.452 and 0.524. Exploratory subgroup analyses provided more favourable but not definitive evidence in favour of the early metformin arm for cohorts with previous GDM and previous caesarean section.

Conclusions: We do not find definitive evidence that early initiation of metformin in addition to usual care for GDM was more cost-effective than usual care alone. The clinical and economic evidence may be considered equivocal, but worthy of further examination.