Accuracy of capillary blood glucose for 50-g glucose challenge test for gestational diabetes screening

Purpose

To assess the accuracy of capillary blood glucose (CBG) compared to conventional venous plasma glucose (VPG) testing for 50-g glucose challenge test (GCT) in gestational diabetes (GDM) screening.

Methods

A total of 300 women were enrolled and 50-g GCT for GDM screening was offered. At 1 h after glucose loading, CBG was evaluated by CONTOUR® PLUS glucose meter by well-trained nurses immediately after venipuncture for VPG. Results of CBG were compared with those from VPG to evaluate its accuracy. Women with venous plasma glucose > 140 mg/dL were offered 100-g OGTT for GDM diagnosis.

Results

The mean age was 30.2 years and the mean gestational age at testing was 21.8 weeks. GDM was diagnosed in 34 women (11.3%). The mean VPG was 142.1 ± 32.9 mg/dL and the mean CBG was 129.3 ± 33.5 mg/dL. Mean difference was -12.3 ± 12.5 mg/dL, corresponding to -8.8 ± 11.4%. CBG significantly correlated with VPG with correlation coefficient of 0.929, p < 0.001. In the detection of abnormal 50-g GCT results (VPG ≥ 140 mg/dL), at 126 mg/dL cutoff, CBG had sensitivity of 92.5%, specificity of 81.8%, and positive and negative predictive values of 82.8%and 92%. None of the GDM would have been missed if CBG was used.

Conclusion

CBG by a certified glucose meter could be considered as an alternative to conventional VPG testing for 50-g GCT for GDM screening using 126 mg/dL cutoff value.

Use of capillary blood glucose for screening for gestational diabetes mellitus in resource-constrained settings

AIMS

The aim of the study was to evaluate usefulness of capillary blood glucose (CBG) for diagnosis of gestational diabetes mellitus (GDM) in resource-constrained settings where venous plasma glucose (VPG) estimations may be impossible.

METHODS

Consecutive pregnant women (n = 1031) attending antenatal clinics in southern India underwent 75-g oral glucose tolerance test (OGTT). Fasting, 1- and 2-h VPG (AU2700 Beckman, Fullerton, CA) and CBG (One Touch Ultra-II, LifeScan) were simultaneously measured. Sensitivity and specificity were estimated for different CBG cut points using the International Association of Diabetes in Pregnancy Study Groups (IADPSG) criteria for the diagnosis of GDM as gold standard. Bland-Altman plots were drawn to look at the agreement between CBG and VPG. Correlation and regression equation analysis were also derived for CBG values.

RESULTS

Pearson's correlation between VPG and CBG for fasting was r = 0.433 [intraclass correlation coefficient (ICC) = 0.596, p < 0.001], for 1H, it was r = 0.653 (ICC = 0.776, p < 0.001), and for 2H, r = 0.784 (ICC = 0.834, p < 0.001). Comparing a single CBG 2-h cut point of 140 mg/dl (7.8 mmol/l) with the IADPSG criteria, the sensitivity and specificity were 62.3 and 80.7 %, respectively. If CBG cut points of 120 mg/dl (6.6 mmol/l) or 110 mg/dl (6.1 mmol/l) were used, the sensitivity improves to 78.3 and 92.5 %, respectively.

CONCLUSIONS

In settings where VPG estimations are not possible, CBG can be used as an initial screening test for GDM, using lower 2H CBG cut points to maximize the sensitivity. Those who screen positive can be referred to higher centers for definitive testing, using VPG.