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.