Diabetes is a group of diseases linked with high blood sugar levels. The number of people affected by diabetes is increasing. Gestational diabetes (GDM) only affects pregnant women. GDM doesn't usually cause symptoms, so a woman might not know she has GDM unless she has a test. We know that GDM causes problems during pregnancy and birth. But recent research also shows GDM can cause health problems for women later in life. Women who develop GDM are at increased risk of developing type 2 diabetes, high blood pressure and heart attacks when compared to women who don't have GDM. This means it is likely that the use of health services such as GP appointments and hospital stays may be higher in women who develop GDM than women who don't, both during pregnancy and later in life. As a result, the costs of treating women with GDM is also likely to be higher than women without GDM. Similarly, there may be implications for the babies of mothers with GDM, such as greater risks of complications at birth. The differences in health outcomes and costs for mothers and babies with and without GDM is currently unclear. The purpose of this project is to quantify the healthcare costs attributable to GDM.
Gestational diabetes mellitus (GDM) is defined as glucose intolerance with onset during pregnancy and resolving after birth. GDM is usually diagnosed by an oral glucose tolerance test (OGTT) at approximately 24-28 weeks gestation. A diagnosis of GDM is made in those who meet a predefined diagnostic threshold, with women diagnosed with GDM typically offered lifestyle advice and encouraged to self-monitor their blood glucose to manage hyperglycemia. GDM is known to be associated with an increased risk of adverse outcomes for mother and infant during pregnancy and birth. Furthermore, women who get GDM are at substantially greater risk of developing type 2 diabetes, hypertension and ischaemic heart disease compared with those who do not develop GDM.
Despite this evidence of elevated risk of disease, the healthcare usage and costs of caring for GDM women (beyond pregnancy) are not known. In this project we aim to quantify these evidence gaps through the healthcare costs associated with women who receive a diagnosis of GDM during pregnancy. We intend to use the Clinical Practice Research Datalink (CPRD), which provides anonymised patient data from a network of GP practices across the UK. The data encompasses 60 million patients, including 16 million currently registered patients. Our application aims to link CPRD data with HES records to determine the differences in resources used and costs between mothers who suffer from GDM and those who do not. The study period is between 2010 and 2021. We will use national reference costs to attribute costs to each type of resource. Once all events have been attributed a cost, we will calculate the cumulative healthcare expenditure for each participant and average annual healthcare expenditure will be compared between groups using generalized linear multivariable (GLM) models, adjusted for potentially moderating factors.
We plan to use primary care data linked to HES data in this project.
We aim to estimate the impact of GDM to healthcare resources and costs. To do so, we require CPRD-HES linked data. The HES requirement includes Admitted Patient Care, Outpatients and Accident & Emergency. The data request ranges from 2008 to 2021, to cover the study period.
We require data on Index Level of Multiple Deprivation, age, smoking, ethnicity to assess heterogeneities across the population. These are important co-variates and so it is important they are included as control variables.
The first step will be to link primary care and secondary care resources to patients. Once we have established differences in resources used, we will attribute costs to the resources.
For primary care visits, costs of consultations will be derived from the Personal Social Services Research Unit (PSSRU) Unit Costs of Health and Social Care 2020 compendium. Prescription costs will be obtained from the Prescription Cost Analysis (PCA) 2020/21 database, electronic searches of the British National Formulary (BNF) 2021 or the Monthly Index of Medical Specialities (MIMS). Where costs are not directly linkable from these sources, literature searches will be conducted.
Secondary care service use will include admitted patient care, outpatients and emergency care services. The HRG4+ grouper will be used to derive Health Resource Groups (HRG) codes which can then be costed using the publicly available National Schedule of NHS costs. Inpatient costs are a function of clinical speciality, admission type, length of stay, procedure codes, etc. For each episode, the National Costs Grouper will produce a relevant HRG as well as a dominant HRG for a spell. We will use the HRGs to cost at the episodic level and then aggregate at the spell level. This will include costs associated with excess bed days, unbundled drugs and devices.
Outpatient costs will be costed on a similar basis. We will use publicly available costs for first, follow-up, telephone clinics. Emergency department costs can be considerable and so we will also include the resources used to treat these patients.
Where appropriate, costs will be adjusted by the Market Forces Factor (MFF) so that cost estimates reflect local market conditions. All costs will be expressed in pound sterling and valued at 2021 prices; earlier unit costs for previous periods will be inflated to 2021 prices using the NHS Hospital Community Pay and Prices Index.
The findings will inform future research, and provide key parameter variables that can be used in the development of cost-effectiveness models that could be used to test novel interventions to prevent GDM and also to reduce the risks of developing associated diseases later in life. The evidence for the costs associated with treating women who get GDM may suggest modifications to current models used to estimate the cost-effectiveness of GDM prevention and treatments. The results will provide important information to women who are pregnant or planning pregnancy, and it will inform the development of clinical guidelines or to help commissioners to judge the cost-effectiveness of potential new pathways of care for GDM.
Nerys Astbury - Chief Investigator - University of Oxford
Nerys Astbury - Corresponding Applicant - University of Oxford
Cynthia Wright Drakesmith - Collaborator - University of Oxford
Lydia Prieto Sepulveda - Collaborator - University of Oxford
Margaret Smith - Collaborator - University of Oxford
Nadeem Hussein - Collaborator - University of Oxford
Stavros Petrou - Collaborator - University of Oxford
Subhashisa Swain - Collaborator - University of Oxford
Cynthia Wright Drakesmith - Collaborator - University of Oxford
Elizabeth-Ann Schroeder - Collaborator - University of Oxford
Margaret Smith - Collaborator - University of Oxford
Nadeem Hussein - Collaborator - University of Oxford
Stavros Petrou - Collaborator - University of Oxford
Subhashisa Swain - Collaborator - University of Oxford
HES Accident and Emergency;HES Admitted Patient Care;HES Outpatient;Patient Level Index of Multiple Deprivation Domains