Glucose challenge test for detecting gestational diabetes mellitus: a systematic review

Abstract

Glucose challenge test for detecting gestational diabetes mellitus: a systematic review Sir, The sensitivity and specificity of screening tests are crucial to adequately detect, and thus efficiently prevent and treat, gestational diabetes mellitus (GDM). The fascinating report by van Leeuwen et al. 1 was a meta-analysis on the 50-g glucose challenge test (GCT), spanning 26 papers. The oral glucose tolerance test (OGTT), following the ingestion of 75 or 100 g of glucose, was used as the reference/diagnostic test for the meta-analysis, which found similar results among studies including women with risk factors and studies with consecutive recruitment: a pooled sensitivity of 0.74 and 0.74, and a pooled specificity of 0.77 and 0.85, respectively. Interestingly, GCT displayed only modest accuracy for GDM screening, with a positive likelihood ratio (LR) of 3.2 and 4.9, and negative LR of 0.34 and 0.32, respectively. As expected, a higher threshold for a positive OGTT increased the sensitivity and decreased the specificity of the GCT.Despite its relatively weak sensitivity and specificity values, the authors concluded that GCT is nevertheless acceptable for screening, but can't replace the OGTT. This conclusion is in agreement with the recent guidelines of the International Association of Diabetes and Pregnancy Study Groups (IADPSG) and the American Diabetes Association (ADA). Both associations recommend OGTT as a one-step screening and diagnosis combination. This limits the scope of the meta-analysis reported by van Leeuwen et al., but the degree of adherence to IADPSG/ADA guidelines has yet to be established.Other limitations are linked to the inherent drawbacks of GCT and OGTT, relating mainly to the length of time required to process blood samples in order to measure blood glucose (BG), as well as the actual time of day when women are tested. It is widely recognised that the nature of a sample (serum/plasma), its storage temperature, the time elapsed between sampling and centrifugation (in-tube glycolysis), and the use of a glycolysis inhibitor are all factors that can alter BG values. The impact of these factors was recently addressed in a study of 60 pregnant women. When tubes were processed systematically and centrifugation performed 5 minutes after blood collection, plasma BG values increased by 10 mg/l, uncovering fifteen cases of diabetes that were previously overlooked when the regular routine was used. 2Another key issue for screening accuracy is linked to the actual time of day when testing is performed. The literature supports a circadian variation of BG in pregnant women, with higher values for GCT and OGTT performed in the afternoon, observed in studies performed in relatively small cohorts.3,4 These all but forgotten results suggested that GCT cut-off values should be adjusted for morning versus afternoon testing. Unfortunately, no further recommendation has ever been issued regarding the best time of day for testing.The bottom line is that GDM may all too often be overlooked for reasons easily circu...

Gestational diabetes mellitus: In search of better screening and diagnostic pathway for Sri Lankan women

“…However, prevalence of macrosomia as the surrogate marker to diagnose GDM is not accurate as many factors including success of the treatment can confound the prevalence of macrosomia. There are other studies showing poor sensitivity of GCT in diagnosing GDM (19,20). A recent study conducted by V Mohan, et al in India showed a very low sensitivity of non-fasting GCT when compared to the IADPSG criteria (sensitivity 22.6%, specificity 97.8%) (21).…”

50 Grams Oral Glucose Challenge Test: Is It an Effective Screening Test for Gestational Diabetes Mellitus?

“…This test is easy to administer and cost-effective for screening purpose [17]. A systemic review by van Leeuwen et al, in 2010 concluded that the 50-g OGCT is acceptable to screen for GDM [18].…”

Gestational Diabetes Mellitus: a review of the diagnosis, clinical implications and management

“…However, for women with GCT above 7.8 mmol/l, only 45% of the women actually had GDM on the OGTT. In a systematic review, the sensitivity of the GCT was only 0.74 while the specificity was 0.77, at the glucose cut-off level of 7.8 mmol/l [18]. As a result, the GCT cannot replace the 75 g OGTT and is gradually being phased out in many centers.…”