Clinical and cost‐effectiveness of non‐invasive cell‐free DNA testing to optimise foetal outcomes for women with monogenic diabetes due to inactivating glucokinase gene mutations: a case series

BACKGROUND: Management of glucokinase-maturity-onset diabetes of the young (GCK-hyperglycaemia, or GCK-MODY) GC in pregnancy relies on knowledge of foetal genotype, which is traditionally estimated by foetal ultrasound measurements with poor diagnostic accuracy. Non-invasive pre-natal testing for GCK-MODY genotype (NIPT-GCK) has recently been developed (Exeter, United Kingdom) and is highly accurate but not currently available in Australia. AIM: We aimed to investigate the clinical and health economic impact of NIPT-GCK MODY testing in Australia. METHODS: A case series of two pregnancies affected by GCK-MODY in pregnancy was conducted. Case 1 had NIPT undertaken at Exeter University, United Kingdom, while case 2 was managed per standard care with ultrasound estimation of foetal genotype. Clinical outcomes and health system costs were obtained from medical and health system records. RESULTS: Case 1 (42-year-old female, G8P1) had GCK-NIPT at 19 weeks, with the baby confirmed to have GCK-MODY. Management was tailored to this result, with a reduced physical and psychological burden of the disease. Case 2 (33-year-old female, gravida 2 para 1) declined NIPT because of cost and had genotype estimated from serial ultrasound methods with post-partum genetic testing required. After adjustment for additional maternal co-morbidities and standardisation of care setting, the GCK-MODY NIPT was cost-effective (-$266) and patient concern and care burden were significantly reduced. CONCLUSIONS: NIPT has the potential to improve diagnostic uncertainty associated with the management of GCK-MODY in pregnancy, reduce the economic and personal burden of intensive foetal monitoring and improve perinatal outcomes.