Diagnostic Accuracy of the Serum-free Androgen Index in Diagnosing Polycystic Ovary Syndrome: An Updated Systematic Review and Meta-analysis

Abstract Aim: To assess the diagnostic accuracy of the free androgen index (FAI) in diagnosing polycystic ovary syndrome (PCOS). Methods: We systematically searched PubMed, Cochrane Library, and Google Scholar databases for relevant studies published up to June 2024. The inclusion criteria were studies that reported the sensitivity and specificity of FAI for PCOS diagnosis. We used a random-effects model to find the pooled sensitivity, specificity, diagnostic odds ratio (DOR), and summary receiver operating characteristic area under the curve (SROC AUC). We determined positive and negative likelihood ratios (NLRs) using the Fagan nomogram and assessed heterogeneity using I 2 statistics. We performed meta-regression and subgroup analysis to explore sources of heterogeneity and used Deeks’ funnel plot to assess publication bias. This study is registered with PROSPERO (ID: CRD42024546829). Results: We included 14 studies with 2870 PCOS patients and 3985 non-PCOS controls. Pooled sensitivity and specificity were 0.81 (95% confidence interval [CI]; 0.73–0.86) and 0.82 (95% CI; 0.72–0.90), respectively. The positive and NLRs were 4.6 (95% CI; 2.8–7.6) and 0.23 (95% CI; 0.17–0.33), respectively. The DOR was 20 (95% CI: 10–39), and the SROC AUC was 0.88 (95% CI: 0.85–0.90). Variability in FAI cutoff values contributed significantly to heterogeneity across studies. Conclusion: Serum FAI is a reliable biomarker for diagnosing PCOS, demonstrating sensitivity and specificity exceeding 80%. It is particularly valuable in primary care settings where ultrasound facility is unavailable. FAI assists in diagnosing biochemical hyperandrogenism, especially in cases where clinical criteria are inconclusive.