Diabetes Care Volume 39, January 2016 55 Lois E. Donovan,1,2 Anamaria Savu,3 Prevalence and Timing of Alun L. Edwards,1 Jeffrey A. Johnson,3 and Screening and Diagnostic Testing Padma Kaul3,4,5 for Gestational Diabetes Mellitus: A Population-Based Study in Alberta, Canada Diabetes Care 2016;39:55–60 | DOI: 10.2337/dc15-1421 OBJECTIVE The extent to which pregnant women are screened for gestational diabetes mel- MANAGEMENT OF GESTATIONAL DIABETES MELLITUS litus (GDM) at the population level is not known. We examined the rate, type, and timing of GDM screening and diagnostic testing in the province of Alberta, Canada. Geographic and temporal differences in screening rates, and maternal risk factors associated with lower likelihood of screening, were also determined. RESEARCH DESIGN AND METHODS Our retrospective linked-database cohort study included 86,842 primiparous women with deliveries between 1 October 2008 and 31 December 2012. Multi- variable logistic regression analysis was used to examine maternal factors asso- ciated with lower likelihood of GDM screening. RESULTS n Overall, 94% ( = 81,304) of women underwent some form of glycemic assessment 1Division of Endocrinology and Metabolism, De- in the 270 days prior to delivery. The majority (91%) received a 50-g glucose screen partment of Medicine, University of Calgary, (GDS). Women not screened were younger and more likely to smoke and had Calgary, Alberta, Canada 2 lower maternal weight and median household income. When a diagnostic 75-g Department of Obstetrics and Gynecology, Uni- versity of Calgary, Calgary, Alberta, Canada oral glucose tolerance test (OGTT) was indicated, it occurred a median of 10 3Canadian VIGOUR Center, University of Alberta, (interquartile range 7, 15) days after the screen. Edmonton, Alberta, Canada 4School of Public Health, University of Alberta, CONCLUSIONS Edmonton, Alberta, Canada 5 GDS occurred widely in a system where it was universally recommended and paid Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada for publicly. When indicated, a 75-g OGTT was completed within 15 days in 75% of fi Corresponding author: Lois E. Donovan, lois. cases. Our nding that this two-step approach was widely implemented in a [email protected]. timely fashion supports continued endorsement of a two-step approach to Received 30 June 2015 and accepted 3 Septem- screening and diagnosis of GDM. Further research is merited to assess whether ber 2015. the one-step GDM diagnostic approach results in different rates and timing of the This article contains Supplementary Data online 75-g OGTT and affects pregnancy outcomes. at http://care.diabetesjournals.org/lookup/ suppl/doi:10.2337/dc15-1421/-/DC1. © 2016 by the American Diabetes Association. The 50-g oral glucose challenge test (GDS) is a common method of screening for Readers may use this article as long as the work is gestational diabetes mellitus (GDM) in North America. This test is recommended for properly cited, the use is educational and not for all women (1) or selectively for the vast majority (at least 90%) of pregnant women profit, and the work is not altered. (2) who have at least one risk factor for GDM (i.e., older age, non-Caucasian, ele- See accompanying articles, pp. 13, 16, vated BMI, history of adverse pregnancy outcomes, and personal or family history of 24, 31, 39, 43, 50, 53, 61, and 65. 56 Prevalence and Timing of Screening for GDM Diabetes Care Volume 39, January 2016 glucose intolerance) (3). Typically this median household income (MHI) as a value of 10.3 mmol/L (185 mg/dL) or screening test is administered between measure of the socioeconomic status of higher occurred, the woman was assumed 24 and 28 weeks’ gestation, but it has the mothers in the cohort (6). to have GDM and no further diagnostic been recommended earlier in gestation testing was required (10). A 2-h 75-g for those with multiple risk factors for Study Design and Population OGTT was recommended for all women GDM (1). If 1 h after the GDS the blood Our retrospective population-based co- whose GDS fell between 7.8 and glucose level is greater than the selected hort study included all primiparous births 10.2 mmol/L (140 and 184 mg/dL). When cutoff (usually 7.2 or 7.8 mmol/L), a sec- in the province of Alberta, Canada, be- women had GDS ,7.8 mmol/L, no further ond step, an oral glucose tolerance test tween 1 October 2008 and 31 December glucose testing was recommended except (OGTT) (with either 75- or 100-g glucose 2012. Alberta is a large, diverse multicul- in circumstances where the GDS was done load) is performed to confirm the diag- tural province in Canada with .3.9 million prior to 24 weeks’ gestation. According to nosis of GDM. Sensitivity and specificity residents (7). A health insurance plan is these criteria, women were diagnosed values of the GDS for predicting the out- paid for by the Alberta Government with impaired glucose tolerance of preg- come on an OGTT range from 70 to 99% that covers all necessary medical service nancy or GDM if they had exactly one, or and 66 to 89%, respectively, depending expenses in the province. Population-level two or more, glucose values, respectively, on the glucose thresholds selected for laboratory data for the entire province ex- on the 75-g OGTT at or above the following the positive screening result and diag- cept for one of the nine health regions glucose thresholds: fasting, 5.3 mmol/L; nostic OGTT (4,5). were available as of 1 January 2008. We 1-h, 10.6 mmol/L; and 2-h, 8.9 mmol/L. There are limited data on the extent restricted the study cohort to birth events to which current practice guidelines for that occurred after 1 October 2008 to al- Statistical Analysis the screening for GDM are implemented low for a complete 9-month assessment We calculated the rates of GDM screen- in clinical practice at the population for gestational screening prior to delivery ing, overall and for each type of test (GDS, level. Accordingly, we evaluated the for all patients. Since screening for GDM is 75-g OGTT without GDS, HbA1c without prevalence, type, and timing of screen- recommended by 28 completed weeks of GDS or 75-g OGTT, and fasting or random ing for GDM and examined temporal pregnancy, women who delivered prior to glucose without GDS, 75-g OGTT, or and geographic differences in a defined 29 gestational weeks were excluded. HbA1c), for our entire study cohort, as geographic area (the province of Al- Women with preexisting diabetes, identi- well as by maternal place of residence berta, Canada) with universal health fied from the APHP antepartum risk (urban or rural) and calendar year. Gesta- care. Our secondary objectives were to assessment, were also excluded. We tional time of GDS and 75-g OGTT was identify maternal risk factors for not un- confined our primary analysis to primip- determined based on the gestational dergoing GDM screening. arous women because we are aware age at time of delivery, the collection that it is the practice of some health date of the laboratory test, and the de- RESEARCH DESIGN AND METHODS care providers in Alberta to treat livery date. When several GDS or 75-g Ethics Statement women with a previous diagnosis of OGTTs were collected, only the earliest Ethics approval for this study was ob- GDM without laboratory retesting in GDS and earliest 75-g OGTT following tained from the University of Alberta in- subsequent pregnancies, since there is GDS within 270 days prior to delivery stitutional review board (Pro00020230). a known high recurrence rate (8). How- were considered in the analysis. The ever, with this caveat in mind, we year of pregnancy was selected as the Data Sources and Linkage did examine GDM screening rates for calendar year of the delivery date. The Maternal personal health care number the entire population (both primiparous delivery date was obtained from labora- was used to link data from a provincial and multiparous) in a secondary analysis. tory data. We examined temporal trends perinatal database, the Alberta Perinatal for screening between 2009 and 2012. Health Program (APHP), with laboratory Outcome Measures Statistical significance of temporal trends data made available by the Data Integra- The primary outcome measure of interest was assessed using a logistic regression tion Measurement and Reporting (DIMR) was the incidence of laboratory screening model with screening as outcome and unit of Alberta Health Services (http:// testing for GDM. A woman was consid- year as the only predictor. www.albertahealthservices.ca) for the ered as having had a GDM screening test Descriptive statistics, specifically mean time period of 1 January 2008 to 31 De- if she had any of the five types of tests for (SD)andmedian(interquartilerange cember 2012. The APHP (www.aphp.ca) glycemic assessment (GDS, 75-g OGTT, [IQR]) for continuous variables and per- captures maternal, obstetrical, and neo- HbA1c, and fasting or random glucose) centages for categorical variables, were natal clinical information from the provin- within 270 days before delivery date. At compared between screened and un- cial delivery record for all hospital and the time the study was conducted, na- screened women using univariate Stu- registered midwife-attended home births tional clinical practice guidelines recom- dent t tests, Kruskal-Wallis test, and x2 in the province of Alberta, Canada. DIMR mended that all pregnant women be test, respectively; all tests of significance holds a central repository of laboratory screened for GDM with a GDS at were two sided, with P values of ,0.05 data for Alberta reported by four regional 24–28 weeks’ gestation (first trimester, if considered significant.