The WHO 2013 oral glucose tolerance test: The utility of isolated glucose measurements - A retrospective cohort study

Abstract

Objective: The WHO 2013 guidelines recommend screening for gestational diabetes mellitus (GDM) by 3-point oral glucose tolerance test (OGTT). The objective of this retrospective cohort study was to evaluate GDM diagnosed by an isolated high glucose.

Study design: We included pregnant women deemed at risk for GDM were offered GDM screening. We examined the records of 1939 consecutively screened pregnancies at two teaching hospitals in Amsterdam during 2016-2020. Using the WHO 2013 diagnostic criteria, we calculated the proportion of GDM cases diagnosed by isolated abnormal glucose values.

Results: Among those screened in our high risk cohort, GDM incidence was 31.5%. Of the GDM diagnoses, 57.0% were based on an isolated fasting glucose value, 30.9% based on multiple raised glucose measurements, 7.4% on an isolated raised 2-hour glucose and 4.7% on an isolated raised 1-hour glucose. For 1-hour glucose, the number needed to screen was 67 persons for one additional GDM case.

Conclusion: The 1-hour glucose in the 3 point OGTT, as suggested by the WHO 2013 guidelines for GDM, contributes only small numbers of GDM cases and a high number needed to screen (67 for 1 additional case in a selective high risk GDM screening strategy), and is likely even less effective in universally screened populations.

Keywords: Gestational diabetes; HAPO study; Oral glucose tolerance test; Overdiagnosis.