Study question: Are HbA1c and fasting glucose (FG) useful in predicting the presence of prediabetes and type 2 diabetes (T2DM) in a large cohort of women with polycystic ovary syndrome (PCOS)?
Summary answer: HbA1c and FG are not suitable as screening tools for prediabetes in a large cohort of PCOS women but do show a good level of agreement with T2DM.
What is known already: Women with PCOS have an increased risk of prediabetes and T2DM. As performing an oral glucose tolerance test (OGTT) is time consuming, HbA1c and FG have been suggested as screening tools for prediabetes and T2DM.
Study design, size, duration: This was a cross-sectional study of 671 women with PCOS conducted from 2006 to 2012.
Participants/materials, setting, methods: The study was carried out at the endocrinological outpatient department of the Medical University of Graz, Austria. We performed 75 g 2-h OGTTs and measured HbA1c in 671 women with PCOS aged 16-45 years with a median BMI of 24.2 (21.3-30.1) kg/m². PCOS was defined according to the Rotterdam criteria. Prediabetes (FG 100-125 mg/dl and/or 2-h glucose 140-199 mg/dl and/or HbA1c 5.7-6.4%) and T2DM (FG ≥ 126 mg/dl and/or 2-h glucose ≥200 mg/dl and/or HbA1c ≥ 6.5%) were diagnosed according to the American Diabetes Association (ADA) criteria. Levels of agreement between different definitions were analyzed using κ-index.
Main results and the role of chance: According to the ADA criteria, we found prediabetes and T2DM in 12.8% (n = 76) and 1.5% (n = 9) of PCOS women, respectively. When using elevated HbA1c (5.7-6.4%) for defining prediabetes, 19 (3.2%) of all PCOS women had prediabetes with a κ-index of 0.36. When using elevated FG (100-125 mg/dl) for defining prediabetes, 31 (5.2%) of all the PCOS women were diagnosed with prediabetes with a κ-index of 0.05. Further, elevated HbA1c (≥6.5% defining T2DM) was found in six (0.9%) PCOS women (κ-index 0.80), and elevated FG (≥126 mg/dl diagnosing T2DM) was found in seven PCOS women (1%; κ-index 0.82).
Limitations, reasons for caution: Our results are limited to an Austrian cohort of PCOS women diagnosed by Rotterdam criteria with a median BMI in the normal weight range.
Wider implications of the findings: Our results are in line with results from previous smaller PCOS cohorts. Our findings do not support the recommendation that FG or HbA1c can be used for the screening of prediabetes in women with PCOS. For such women, OGTT should be performed for screening of prediabetes. Whether this finding is generalizable to other cohorts remains to be determined in further studies.
Keywords: HbA1c; oral glucose tolerance test; polycystic ovary syndrome; prediabetes; type 2 diabetes.