#Grand Rounds

Glucose Tolerance Test Alternatives During the COVID-19 Pandemic (and Beyond)?

BACKGROUND AND PURPOSE:

Oral glucose tolerance tests can be challenging during the COVID-19 pandemic due to social distancing restrictions
- National guidelines for many countries recommend alternative options for hyperglycemia screening
Meek et al. (Diabetic Medicine, 2020) evaluated the diagnostic and prognostic performance of oral glucose tolerance tests alternatives

Retrospective study
Data sources
- Cambridge University Hospital NHS Foundation Trust (CUHFT) data
- OPHELIA prospective observational study, UK
Participants
- From CUHFT: Singleton pregnancies with GDM
- From OPHELIA: Women with ≥1 GDM risk factor
Study design
- Receiver-operating characteristic (ROC) curves and unadjusted logistic regression were used to compare
  - Random plasma glucose
  - Fasting plasma glucose
  - HbA1c performance
Primary outcomes
- Gestational diabetes (NICE or International Association of Diabetes and Pregnancy Study [IADPS] Groups criteria)
- Diabetes in pregnancy (WHO criteria)
- Cesarean delivery
- LGA
- Neonatal hypoglycemia
- NICU admission

In CUHFT: 17,736 singleton pregnancies | 826 GDM pregnancies
In OPHELIA: 361 women with ≥1 GDM risk factor
GDM diagnosis was significantly associated with
- Random plasma glucose at 12 weeks
  - AUROC (NICE and IADPS) 0.81 (95% CI, 0.79 to 0.83)
- Fasting plasma glucose
  - AUROC (NICE): 0.75 (95% CI, 0.65 to 0.85)
  - AUROC (IADPS): 0.92 (95% CI, 0.85 to 0.98)
- HbA1c at 28 weeks’ gestation
  - AUROC (NICE): 0.83 (95% CI, 0.75 to 0.90)
  - AUROC (IADPS): 0.84 (95% CI, 0.77 to 0.91)
For a 5% GDM detection rate (similar to detection rate using standard oral glucose testing) the following cut-offs would be required
- At 12 weeks: Random plasma glucose ≥8.5 mmol/l (153 mg/dL | Sensitivity 42%; Specificity 96%
- At 28 weeks
  - HbA1c ≥39 mmol/mol (5.7%) | Sensitivity 26%; Specificity 96%
  - Fasting plasma glucose ≥5.2–5.4 mmol/l (93.6 mg/dL to 97.2 mg/dL) | Sensitivity 18–41%; Specificity 97–98%
These measures predicted some of the pregnancy outcomes

The following alternative testing strategies can identify pregnant women with hyperglycemia at risk of adverse pregnancy outcomes vs oral glucose testing
- Random plasma glucose at 12 weeks
- Fasting plasma glucose
- HbA1c at 28 weeks
The authors state that while all 3 approaches can predict obstetric and neonatal outcomes, practice should not be changed post-pandemic without further research and long term data

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