Objective
This study investigated the cost-effectiveness of treating mild gestational diabetes mellitus (GDM).
Study Design
A decision analytic model was built to compare treating vs not treating mild GDM. The primary outcome was the incremental cost per quality-adjusted life year (QALY). All probabilities, costs, and benefits were derived from the literature. Base case, sensitivity analyses, and a Monte Carlo simulation were performed.
Results
Treating mild GDM was more expensive, more effective, and cost-effective at $20,412 per QALY. Treatment remained cost-effective when the incremental cost to treat GDM was less than $3555 or if treatment met at least 49% of its reported efficacy at the baseline cost to treat of $1786.
Conclusion
Treating mild GDM is cost-effective in terms of improving maternal and neonatal outcomes including decreased rates of preeclampsia, cesarean sections, macrosomia, shoulder dystocia, permanent and transient brachial plexus injury, neonatal hypoglycemia, neonatal hyperbilirubinemia, and neonatal intensive care unit admissions.
Gestational diabetes mellitus (GDM), defined as glucose intolerance that first occurs or is first identified in pregnancy, is thought to occur in 2-5% of all pregnancies and along with the rate of obesity is rising in frequency in the United States. It is associated with higher rates of preeclampsia, operative deliveries, macrosomia, shoulder dystocia, and birth injuries.
Current recommendations from the American College of Obstetricians and Gynecologists are that all patients be screened during the second trimester of pregnancy, those that screen positive have a confirmatory test, and those that are diagnosed with GDM be treated first by medical nutrition therapy (diet), and if that fails, then with insulin. However, the US Preventative Services Task Force in their 2008 recommendation stated that there was insufficient evidence to support screening for GDM and that it was uncertain whether treatment led to improved health outcomes.
Until recently the best evidence for treating GDM was from a multicenter study (Australian Carbohydrate Intolerance Study in Pregnant Women [ACHOIS]) that randomized women diagnosed with “glucose intolerance of pregnancy” by pre-1998 World Health Organization (WHO) criteria (fasting glucose <140 mg/dL and a 75 g, 2 hour oral glucose tolerance test between 140 and 198 mg/dL) to treatment vs no treatment. The results showed that treating these women with GDM with dietary advice, glucose monitoring, and insulin if necessary reduced serious perinatal morbidities, including neonatal death, shoulder dystocia, bone fracture, and nerve palsy.
A more recent (2009) multicenter randomized controlled trial (RCT) investigated women with mild GDM, defined as a normal fasting glucose (<95 mg/dL) but 2 or more values exceeding the postprandial thresholds of the Carpenter-Coustan criteria after a 100 g, 3 hour oral glucose tolerance test, which is commonly used in the United States as opposed to the WHO criteria. Women were assigned to receive formal nutritional counseling, diet therapy, and insulin if required (treatment group) or usual prenatal care (control group). The results showed that treating mild GDM resulted in reduced risks of fetal overgrowth, shoulder dystocia, cesarean delivery, and hypertensive disorders.
In the setting of wide variations in the definition and management of GDM, cost-effectiveness analyses on the results of clinical trials are an integral component of public policy decision making. Understanding the cost-effectiveness of treating mild GDM is particularly important because a normal fasting glucose in the setting of abnormal postprandial glucose levels represents the margin of GDM care because its definition and clinical implications continue to evolve as a result of ongoing research efforts. To date, there has been no cost-effectiveness analysis on treating mild GDM based on the most recent clinical trial results.
Materials and Methods
A decision-analytic model ( Figure 1 ) from the societal perspective was created using TreeAge Pro (version 2009; TreeAge, Williamstown, MA) to simulate a cohort of pregnant women diagnosed with mild GDM and divided into a treatment and no treatment arm. Because no human subjects were involved in creating this theoretical model, this study was exempt from institutional review board approval. Maternal outcomes in the model included preeclampsia, shoulder dystocia, cesarean vs vaginal delivery, and maternal death. Neonatal outcomes included macrosomia (>4000 g), permanent or transient brachial plexus injury, hypoglycemia, admission to a neonatal intensive care unit (NICU), hyperbilirubinemia, and neonatal death. All probabilities, costs, and utilities were derived from the literature. A cost-effectiveness threshold of $100,000 per quality-adjusted life year (QALY) was used.
Probabilities
The baseline probabilities for preeclampsia, macrosomia, cesarean delivery, neonatal death, and NICU admission and how treatment affected these probabilities were derived directly from a 2009 RCT on treating mild GDM ( Table 1 ). Because the presence of macrosomia affects the probability of shoulder dystocia, brachial plexus injury, hypoglycemia, and hyperbilirubinemia, these probabilities were derived from a separate body of work that examined these factors independently in patients with GDM ( Table 2 ). To estimate the effect of GDM treatment on shoulder dystocia, brachial plexus injury, hypoglycemia, and hyperbilirubinemia, their baseline probabilities were multiplied by the relative risk associated with treatment published in the 2009 RCT. Although treating mild GDM affected the probability of brachial plexus injury occurring, once it occurred, the probability that it would be permanent (vs transient) did not change because there were no data to support how treatment affected the severity of a brachial plexus injury. Probabilities for maternal death were derived from the literature.
| Parameter | Probabilities | Utilities | Costs | Reference | |
|---|---|---|---|---|---|
| GDM treatment | $1786 | ||||
| Maternal outcomes | Without treatment | With treatment | |||
|---|---|---|---|---|---|
| Preeclampsia | 0.136 | 0.086 | $19,184 | ||
| Cesarean delivery | 0.338 | 0.269 | 0.99 | $11,979 | |
| Vaginal delivery | 1 | $7790 | |||
| Maternal death | |||||
| Cesarean | 0.000022 | 0.000022 | 0 | $100,000 | |
| Vaginal | 0.000002 | 0.000002 | 0 | $100,000 | |
| Shoulder dystocia | |||||
| With macrosomia | 0.105 | 0.03885 | |||
| Without macrosomia | 0.016 | 0.00592 |
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