Diagnostic accuracy of oral glucose tolerance tests, fasting plasma glucose and haemoglobin A1c for type 2 diabetes in women with polycystic ovary syndrome: A systematic review and meta-analysis

Aims: To inform international guidelines, a systematic review and meta-analysis was conducted to assess the performance of diagnostic methods for type 2 diabetes in women with polycystic ovary syndrome (PCOS). Methods: An updated systematic search was conducted on five databases from 2017 until October 2023 and combined with prior searches (from inception). Meta-analyses of diagnostic accuracy tests were conducted. Results: Nine studies comprising 2628 women with PCOS were included. Against the oral glucose tolerance test, a haemoglobin A1C (HbA1c) ≥ 6.5% had a pooled sensitivity of 50.00% (95% confidence interval (CI): 35.53–64.47), specificity of 99.86% (95%CI: 99.49–99.98), and positive and negative predictive values of 92.59% (95%CI: 75.27–98.09) and 98.27% (95%CI: 97.73–98.68), respectively, with an accuracy of 98.17% (95%CI: 97.34–98.79). Fasting plasma glucose values ≥ 7.0 mmol/L had a pooled sensitivity of 58.14% (95%CI: 42.13–72.99), specificity of 92.59% (95%CI: 75.35–98.08), positive and negative predictive values of 92.59% (95%CI: 75.35–98.08) and 99.09% (95%CI: 98.71–99.36), respectively, and an accuracy of 99.00% (95%CI: 98.46–99.39) against the oral glucose tolerance test. Conclusions: To our knowledge, this is the first systematic review assessing the performance of diagnostic methods for type 2 diabetes in women with PCOS. We demonstrate that using a cut-off for HbA1c of ≥6.5% in this population may result in misdiagnosis of half of the women with type 2 diabetes. Our results directly informed the recommendations of the 2023 International PCOS Guideline, suggesting that the oral glucose tolerance test is the optimal method for screening and diagnosing type 2 diabetes in women with PCOS and is superior to fasting plasma glucose and HbA1c.