A postnatal fasting plasma glucose is useful in determining which women with gestational diabetes should undergo a postnatal oral glucose tolerance test

Abstract

In our population, a 6-week postnatal fasting plasma glucose is useful in determining which women with gestational diabetes should undergo an OGTT. Consequently we now perform OGTT only in women whose postnatal fasting plasma glucose is > or =6.0 mmol/l.

Performance Characteristics of Postpartum Screening Tests for Type 2 Diabetes Mellitus in Women with a History of Gestational Diabetes Mellitus: A Systematic Review

“…Five studies 22, 24, 29, 30, 32 compared the FBG ≥ 7.0 mmol/L (≥ 126 mg/dL)7 to a 2-hr 75-gm OGTT with a fasting threshold ≥ 7.8 mmol/L (≥ 140 mg/dL) and a 2-hr plasma glucose > 11.1 mg/dL (> 200 mg/dL) 21. (Tables 1 and 2) These studies consistently reported high specificity of the FBG (range: 94 to 99 percent) with very few “false positives.” (Figure 3) However, the sensitivities of the FBG alone ranged from 14 to 100 percent.…”

“…Holt et al was the only study that reported a measure of reproducibility. The coefficient of variation for the plasma glucose assay was 1.2 percent at 3.3 mmol/L (59.4 mg/dL) and 1.5 percent at 16.5 mmol/L (297 mg/dL), which reflects low variability 24. No included studies compared the reproducibility of the FBG with the OGTT, which included a 2-hr plasma glucose value.…”

“…A single study24 included in our review reported the coefficient of variation for the plasma glucose assay, but no study reported the reproducibility of the FBG or OGTT in their population. A study by Corcoy et al, which did not meet inclusion criteria for this review, focused on examining the reproducibility of the 2-hr 75-gm OGTT according to the 1999 WHO criteria for diagnosing type 2 diabetes in women with a history of gestational diabetes 38.…”

“…Clinically, it is not yet clear whether identification of this asymptomatic pre-diabetes state will alter provider recommendations or change outcomes 16. Second, there were seven studies, 22-24 27, 29, 30, 32 that used a FBG threshold value ≥ 7.8 mmol/L (≥ 140 mg/dL) as part of the 2-hr 75-gm OGTT. This test may no longer be clinically useful as current guidelines recommend a threshold ≥ 7.0 mmol/L (126mg/dL) as part of the 2-hr 75-gm OGTT 6, 7.…”

“…This test may no longer be clinically useful as current guidelines recommend a threshold ≥ 7.0 mmol/L (126mg/dL) as part of the 2-hr 75-gm OGTT 6, 7. However, these articles met our inclusion criteria and the comparisons with the FBG still provide information about the additive value of the 2-hr plasma glucose 22, 24, 29, 30, 32. Third, overall study quality was limited by sampling methods involving use of convenience samples that had high losses to followup.…”