Cost-Effectivity Analysis of One-Step Versus Two-Step Screening for Gestational Diabetes

Objective: Early diagnosis of gestational diabetes mellitus (GDM) is important for both maternal and fetal health. The literature has varying recommendations about one-step and two-step tests for GDM screening and diagnosis. The present study aimed to investigate the difference in the cost and duration of hospital stay of a one-step procedure compared to a two-step procedure, which is routinely performed in our hospital. Materials and Methods: The two-step procedure was performed in 2,724 pregnant women, and the one-step procedure was performed in 185 pregnant women. The one-step and two-step screening procedures for gestational diabetes were compared with respect to the duration of hospital stay and cost. Results: The test cost per woman was 0.75 TL less in the one-step procedure; however, the duration of the one-step test was 18.6 min longer, and the number of blood sampling procedures was 1.08 times higher. Conclusion: The one-step method may be preferred over the two-step (or glucose challenge) test due to its diagnostic value and lower cost.


Introduction
Gestational diabetes mellitus (GDM) is carbohydrate intolerance that either begins or is first diagnosed during pregnancy.If untreated, this hyperglycemic condition leads to an increase in perinatal morbidity and mortality [1].Additionally, women with a history of GDM have a 3.5-fold increased risk of developing DM compared to the normal population [2].Therefore, the identification and early diagnosis of GDM are important for both maternal and fetal health.
Because of the discrepancy in diagnostic criteria, it is difficult to estimate the global prevalence of GDM.Studies performed in different regions of the world using different diagnostic criteria have reported prevalence rates ranging between 2% and 18% [3][4][5][6].It has also been reported that the prevalence of GDM has been gradually increasing [7].Risk factors for GDM include obesity, age >35 years, a previous history of neonatal death, and a previous history of cesarean section.Younger age groups have a lower risk for GDM [6].The prevalence of GDM was found to be 0.85% in a Turkish study of 1,653 young women (≤19 years) [8].Akbay et al. [9] reported a GDM prevalence of 8.9% among Turkish women by measuring plasma glucose levels in a two-step oral glucose tolerance test based on Carpenter-Coustan criteria.
A worldwide consensus on the diagnostic criteria of and recommended screening test for GDM in pregnant women has not yet been reached, and new diagnostic criteria are being introduced over time [10,11].Although the oral glucose tolerance test (OGTT) is widely accepted for the diagnosis of DM, strategies are being investigated to avoid exposure of pregnant women to non-physiological glucose loads.Various studies comparing the 75 g OGTT, 100 g OGTT, glucose stick, and 50 g glucose monomer or polymer drink tests have reported that there is not yet sufficient evidence to determine which method is best [12].
In literature authors have different recommendations about one-step or two-step tests for GDM screening and diagnosis.The American Diabetic Association (ADA) recommends a 50 g oral glucose load screening followed by a three-hour 100 g OGTT in those with positive screening results.ADA recommendations also include a two-hour 75 g OGTT [1].For the diagnosis of GDM, the World Health Organization (WHO) recommends a plasma glucose measurement after overnight fasting (8-14 hours) and two hours after giving 75 g anhydrous glucose in 250-300 mL water [13].According to the criteria recommended by the Association of Diabetes and Pregnancy Groups (IADPSG) in 2010, GDM can be diagnosed based on at least one abnormal 75 g OGTT value (fasting, one-hour and two-hour plasma glucose levels of ≥92, 180 and 153 mg/dL, respectively) [14].
The routine practice in our hospital is to perform a 100 g OGTT in pregnant women with a glucose level ≥140 mg at 60 minutes after the 50 g oral glucose load.The present study aimed to investigate the cost and duration of hospital stay of a one-step procedure with 75 g OGTT compared to the twostep procedure.

Materials and Methods
In Zekai Tahir Burak Women's Health Education and Research Hospital, the two-step OGTT procedure was performed in 2,724 pregnant women and the one-step OGTT was performed in 185 pregnant women during a four-month period in 2009 at the antenatal care unit.We excluded patients who were members of an ethnic group with a high prevalence of GDM, had first degree relatives with known diabetes, had a body mass index >25, were older than 35 years, or had a history of poor obstetric outcome.The homo-geneous patient population, a result of the strict exclusion criteria of the study, created a low-risk study group for the screening of GDM.Allocation into the two groups was determined by asking the patient's preference regarding these two glucose tolerance screening methods.During the first step, blood samples were obtained 60 min after a 50 g oral glucose load.The cost of this first step was found to be 15 TL per woman.Patients with a blood glucose level ≥140 mg/ dL underwent a 100 g OGTT.Blood samples were obtained at 0, 60, 120, and 180 min.During the same time period, 185 pregnant women underwent a 75 g OGTT, and blood samples were also obtained at 0, 60, and 120 min.Based on these data, the one-step and two-step procedures were compared with respect to the duration and costs.
Statistical analysis was performed with IBM SPSS Statistics Software (19.0, SPSS Inc., Chicago, IL, USA).The results are presented as the mean values and compared with the independent samples t test.P values <0.05 were considered statistically significant.

Results
Of the 2,724 pregnant women who underwent the 50 g oral glucose load screening, 23% (n=628) required a 100 g OGTT.A 75 g OGTT was performed in 185 pregnant women.The comparison of the one-step and two-step procedures with respect to the duration and costs is shown in Figure 1.The results are summarized in Table 1.
The cost of the test per woman was 0.75 TL less in the one-step procedure, but the duration of the one-step test was 18.6 min longer and the number of blood sampling procedures was 1.08 times higher.

Discussion
Among GDM screening tests, the procedure recommended by the WHO is accepted as a simple and cost-effective test, and the only disadvantage is that the pregnant woman has to undergo the test in a fasting state.Anjalakshi et al. [ compared the two-hour 75 g OGTT recommended by the WHO and a two-hour 75 g OGTT performed regardless of the time of the last meal and showed no significant difference in the glycemic profile.It has been proposed that the twohour 75 g OGTT performed regardless of the time of the last meal is the least disruptive method for the pregnant woman.Similarly, Balaji et al. [16] conducted a study in India with a modified version of the WHO criteria.In that particular study, blood samples were obtained two hours after a 75 g oral glucose load was given regardless of the time of the last meal, and the diagnosis of GDM was established in those with a plasma glucose level ≥7.8 mmol/L.The authors reported that establishing the diagnosis based on a single blood sample was cost-effective.Meltzer et al. [17] conducted a randomized controlled trial and compared one-step and two-step methods of GDM screening and diagnosis.The results of the screening showed that the two-step method (with 75 or 100 g of glucose) had a lower cost compared to the one-step method (two-hour OGTT).The authors reported that the one-step method required longer times and more blood draws.A cost-effectiveness analysis of four screening strategies was performed by Nicholson et al. [18].These strategies included a no-screening strategy, the 75 g OGTT strategy, the 100 g OGTT strategy and the sequential strategy (initial 50 g glucose challenge test followed by, in those who test positive, a 100 g OGTT), and the authors reported that the sequential strategy was cost-effective and that the 100 g OGTT strategy might also be a cost-effective alternative strategy in populations with a high prevalence of GDM.By also considering the level of individual patient risk, Round et al. [19] investigated the cost-effectiveness of eight screening strategies, including a no-screening strategy.While the no-screening strategy was cost-effective when the risk for GDM was <1%, fasting plasma glucose followed by OGTT was most likely to be a cost-effective strategy when the risk was between 1% and 4.2%.The universal OGTT was most likely to be cost-effective when the risk for GDM was >4.2%.
The present study showed that the single-step procedure required an 18.6 min longer interval and 1.08 times more blood draws, but it was associated with a 0.75 TL lower cost.Our study group was a low risk group for GDM, which was comprised of subjects who did not possess the exclusion criteria related to increased GDM risk.The exclusion of patients with a high risk for GDM is a limitation of our study, and randomized controlled studies comparing the cost-effectiveness of one-step and two-step glucose challenge tests among low risk and high risk patients are also needed in the future.It has been reported that the glucose challenge test might overlook 13% to 17% of the cases according to the criteria used [20].Considering the importance of accurately diagnosing GDM for the health of the mother and baby, the one-step method can be utilized instead of the glucose challenge test or the two-step test due to its diagnostic value and lower cost, although it requires a longer time and more blood draws.

Figure 1 .
Figure 1.Comparison of one-step and two-step procedures with respect to the duration and cost.

Table 1 . Comparison of one-step and two-step procedures (Zekai Tahir Burak Women's Health Education and Research Hospital, 2009)
15] *: p values are calculated with the independent samples t test