Fasting plasma glucose and risk factor assessment: Comparing sensitivity and specificity in identifying gestational diabetes in urban black African women

Abstract

Background. Identifying women with gestational diabetes mellitus (GDM) allows interventions to improve perinatal outcomes. A fasting plasma glucose (FPG) level ≥5.1 mmol/L is 100% specific for a diagnosis of GDM. The International Association of Diabetes and Pregnancy Study Groups acknowledges that FPG <4.5 mmol/L is associated with a low probability of GDM. Objectives. The validity of selective screening based on the presence of risk factors was compared with the universal application of FPG ≥4.5 mmol/L to identify women with GDM. FPG ≥4.5 mmol/L or the presence of one or more risk factors was assumed to indicate an intermediate to high risk of GDM and therefore the need for an oral glucose tolerance test (OGTT). Methods. Consecutive black South African (SA) women were recruited to a 2-hour 75 g OGTT at 24 -28 weeks' gestation in an urban community health clinic. Of 969 women recruited, 666 underwent an OGTT, and of these 589 were eligible for analysis. The glucose oxidase laboratory method was used to measure plasma glucose concentrations. The World Health Organization GDM diagnostic criteria were applied. All participants underwent a risk factor assessment. The χ 2 test was used to determine associations between risk factors and a positive diagnosis of GDM. The sensitivity and specificity of a positive diagnosis of GDM were calculated for FPG ≥4.5 mmol/L, FPG ≥5.1 mmol/L, and the presence of one or more risk factors. Results. The prevalence of overt diabetes mellitus and GDM was 0.5% and 7.0%, respectively. Risk factor-based selective screening indicated that 204/589 (34.6%) of participants needed an OGTT, but 18/41 (43.9%) of positive GDM diagnoses were missed. Universal screening using the FPG threshold of ≥4.5 mmol/L indicated that 152/589 (25.8%) of participants needed an OGTT, and 1/41 (2.4%) of positive diagnoses were missed. An FPG of ≥5.1 mmol/L identified 36/41 (87.8%) of GDM-positive participants. The sensitivity and specificity of the presence of one or more risk factors were 56% and 67%, respectively. The sensitivity and specificity of FPG ≥4.5 mmol/L were 98% and 80%, respectively. Conclusions. Universal screening using FPG ≥4.5 mmol/L had greater sensitivity and specificity in identifying GDM-affected women and required fewer women to undergo a resource-intensive diagnostic OGTT than risk factor-based selective screening. A universal screening strategy using FPG ≥4.5 mmol/L may be more efficient and cost-effective than risk factor-based selective screening for GDM in black SA women.

The influence of maternal blood glucose during pregnancy on weight outcomes at birth and preschool age in offspring exposed to hyperglycemia first detected during pregnancy, in a South African cohort

“…However, there are currently no prediction models for Africa populations and most of the existing prediction models lack external validity [ 34 ]. Recent data from Johannesburg suggest that the use of a dual-threshold fasting plasma glucose, ≥4.5mmol/L to rule out, and 5.1mmol/L to rule in GDM, may result in only 2.4% missed cases of GDM [ 21 ]. Using fasting blood glucose only for the diagnosis of HFDP will be less costly than the standard OGTT, and maybe a useful solution in the meantime.…”

“…In South Africa, recent epidemiological studies reported prevalences of HDFP and GDM of 26% [ 16 ] and 9% [ 15 ], respectively, suggesting that up to a quarter of pregnancies may be complicated by HFDP. Since most provinces in the country use a selective risk factor screening approach and consequently may miss up to 50% of women with HFDP, a substantial proportion of children are likely to be exposed to untreated HFDP [ 21 ]. This study was undertaken to contribute to the understudied area of the cardiometabolic outcomes of children from HFDP in South Africa and elsewhere in Africa.…”

Perspectives on gestational diabetes mellitus in South Africa

“…The growing body of research in the field of HFDP over the past decade has highlighted numerous shortfalls in healthcare delivery in SA, in addition to the health burden and consequences of HFDP. [5][6][7][8][9][10][11][12][13][14] The significance of HFDP lies in the well-established short-and more recently explored long-term ramifications for both mother and child, ultimately augmenting the intergenerational risk of cardiometabolic diseases. Of profound concern is that HFDP is fuelling the type 2 diabetes mellitus (T2DM) epidemic, with over half the mothers developing diabetes within the first decade following delivery, making HFDP one of the strongest predictors of T2DM.…”

“…Fortunately, there is now a growing body of research in SA highlighting the burden and risk factors for HFDP, as well as maternal, neonatal and early childhood outcomes following HFDP. [5,6,8,10,11,14,[25][26][27][28][29][30][31] The burden of HFDP in SA Urbanisation and recent socioeconomic changes in SA have fuelled a rapid nutritional transition that has been accompanied by a dramatic shift in the burden of disease from communicable diseases, such as HIV, to non-communicable diseases (NCDs) such as diabetes mellitus and HFDP. [32] Prevalence studies of HFDP for SA are limited to seven studies in the past four decades, [8,13,[26][27][28][29]33] in which the prevalence ranged from 1.8% to 25.8% owing to varying screening strategies and diagnostic tests being employed.…”

An Update on Screening Strategies for Gestational Diabetes Mellitus: A Narrative Review

“…More recently, a prospective study in South-African women confirmed that universal screening using FPG ≥ 4.5 mmol/L had greater sensitivity and specificity in identifying GDM-affected women and required fewer women to undergo a resource-intensive diagnostic OGTT than risk-factor-based selective screening. 90 Likewise, a retrospective study found that risk factor screening for GDM alone or in combination with random capillary glucose was poorly predictive of GDM, but FPG 4.8–5.0 mmol/l showed good test characteristics and resulted in a low rate of OGTTs needed. 91 A study evaluating FPG as a screening tool to rule-out GDM in a low-risk population found that women with FPG ≤3.4 mmol/L were at low risk of developing GDM with a sensitivity of 91.3%, thereby avoiding a two-step screening in 10% of their population.…”