Endocrine Abstracts

Introduction: A two-step approach is usually used to diagnose GDM. At 24–28 weeks of pregnancy, a 50 g 1-hour glucose or O’Sullivan test is performed. If it is positive (≥140 mg/dl), it is followed by a 100 g-3 hours-Oral Glucose Tolerance Test (OGTT) which is considered positive if at least two or more values are ≥ of reference values (105-190-165-145 mg/dl). Despite it is not include in any clinical practice guideline, sometimes the 100 g OGTT is obviated if O’Sullivan is ≥200 mg/dl.

Objective: To evaluate the usefulness of O’Sullivan≥200 for diagnosis of GDM.

Material and methods: We analyzed data from 2774 patients presenting O’Sullivan test positive, who were carried out the 100g-OGTT at Virgen de la Victoria Hospital from 2015 to 2017 in order to compare 100g-OGTT vs O’Sullivan≥200 for diagnosis of GDM. In addition, we compared maternal and perinatal characteristics of 3 groups of patients: O’Sullivan<200 and non-pathological 100g-OGTT (A), O’Sullivan≥200 and non-pathological 100g-OGTT (B) and O’Sullivan≥200 and pathological 100g-OGTT (C).

Results: From 2774 patients with O’Sullivan test positive, 523 (18.9%) presented pathological 100g-OGTT and 2251 (81.1%) non-pathological. From 140 patients with O’Sullivan≥200, 83 (59.3%) presented pathological 100g-OGTT and 57 (40.7%) non-pathological. Therefore, the parameters of internal validity of O’Sullivan≥200 were: sensitivity 15.8%, specificity 97.4%, positive predictive value 59.2%, negative predictive value 83.3%, false-positive rate 2.5%, false-negative rate 84.1%. Comparison between groups: table 1. We only observed patients from group A to be significantly younger than those from groups B and C.

Conclusions: - If O’Sullivan ≥200 is considered as diagnosis of GDM, in order to avoid the 100g OGTT, 4.1 in every 10 pregnant women would be falsely diagnosed of GDM, causing unnecessary concern in patients and, probably, and an increase in GDM prevalence probably unacceptable by gestational diabetes units.

- O’Sullivan ≥200 is not useful to identify pregnant women with a higher obstetric risk.