Supplementary Material for: Diagnostic performance of Adrenal Gland cytology following the World Health Organisation (WHO) standardized categories – Systematic review and Meta-analysis

Introduction: Fine needle aspiration cytology (FNAC) reporting systems for adrenal gland cytology lack global uniformity. Implementing a standardized global reporting system would improve diagnostic accuracy, risk assessment, clinical communication, and uniformity in adrenal gland cytology practices worldwide. The current systematic review and meta-analysis aimed to assess the proposed WHO standardized reporting categories for adrenal gland cytology and evaluate the role of FNAC in adrenal lesion diagnosis. Material and Methods: A comprehensive search was conducted in PubMed, Scopus, and Embase databases up to June 2024. Studies with more than 15 patients were included. The QUADAS-2 tool was employed for quality assessment of the selected studies. Heterogeneity and publication bias among the studies were also evaluated. Cytological categories were recategorized according to the proposed WHO reporting system. Pooled sensitivity, specificity, and risk of malignancy (ROM) ranges for each cytological category were calculated. Results: Fifteen studies met the inclusion criteria. Pooled diagnostic performance across studies showed high sensitivity (92.2%) and high specificity (99.5%). Heterogeneity and publication bias were low. Range and pooled ROM across cytology categories were: Inadequate/nondiagnostic/unsatisfactory - 0% to 100% (18%), Benign – 0% to 14.7% (3.7%), Atypical category - 0% to 50% (46.2%), “Suspicious for malignancy” - 0% to 100% (76.5%), and Malignant category - 94.4% to 100% (99.6%) Conclusion: High sensitivity and specificity, as well as ROM values across categories, demonstrate that the proposed WHO cytological categories offer reliable risk stratification for adrenal lesions, supporting accurate diagnosis and treatment decisions. The low heterogeneity and minimal publication bias ensure that the findings are applicable across various clinical settings and patient populations.