Screening for gestational diabetes mellitus in a South African population : prevalence, comparison of diagnostic criteria and the role of risk factors

Abstract

BACKGROUND. The prevalence of gestational diabetes mellitus (GDM) is increasing. Most major world organisations now recommend universal screening for GDM based on the International Association of Diabetes in Pregnancy Study Groups (IADPSG) criteria. Currently there is a lack of consensus on the diagnostic criteria for GDM used in South Africa (SA). The Society for Endocrinology, Metabolism and Diabetes of South Africa’s revised guidelines recommend the use of the IADPSG criteria for the diagnosis of GDM. OBJECTIVES. To determine the prevalence of GDM in an SA population. We compared the prevalence of GDM using the various diagnostic criteria and evaluated the risk factors associated with GDM. METHODS. This was a prospective cohort observational study carried out at a level 1 clinic in Johannesburg, SA. All pregnant women at <26 weeks’ gestation were recruited. Patients known to have GDM were excluded. At recruitment, a data questionnaire was completed and bloods were drawn for a random glucose test and measurement of the glycated haemoglobin level. A 75 g 2-hour oral glucose tolerance test (OGTT) was scheduled before 28 weeks’ gestation. RESULTS. Five hundred and fifty-four patients (55.4%) completed the OGTT. The prevalence of GDM was 25.8% if universal screening and the IADPSG criteria were used. If universal screening and the National Institute for Health and Care Excellence (NICE) criteria were used, the prevalence was 17.0%. If selective risk factor-based screening was used, only 254 (45.8%) of the women would have had an OGTT. The prevalence of GDM in this instance would have been 15.2% with the IADPSG criteria and 3.6% with the NICE criteria. Two hundred and fifty-four patients (45.8%) had at least one risk factor for GDM. The presence of one or more risk factors had a poor sensitivity (58.7%) and specificity (58.6%) for the detection of GDM in our study population. CONCLUSIONS. The prevalence of GDM would be substantially increased if universal screening with the IADPSG criteria were to be employed. Risk factors are a poor screening test for GDM.