Supplementary Material for: Systematic Review and Meta-Analysis of the Diagnostic Accuracy of the Sydney System for Reporting Lymph Node Fine-Needle Aspiration Biopsy in Diagnosing Malignancy

Introduction To perform the first meta-analysis for assessment of the pooled risk of malignancy of each category of the Sydney system for reporting of lymph nodal aspirates along with evaluation of diagnostic accuracy. Methods Pubmed/ MEDLINE and Embase were searched with the following keywords “(Lymph node) AND ("fine needle aspiration biopsy" OR FNAB) OR (International system OR Sydney system)” in the timeframe 2020 to August 04, 2023. The selected articles were assessed for risk of bias by the QUADAS-2 tool. The meta-analysis for sensitivity and specificity for each cut-off, that is, “Atypical considered positive,” “Suspicious of Malignancy considered positive,” and “Malignant considered positive” for the lesions was carried out after excluding the inadequate samples in each study. To assess the diagnostic accuracy, summary receiver operating characteristic (sROC) curves were constructed, and the diagnostic odds ratio (DOR) was pooled in both scenarios. Results Nine studies, all of which were retrospective cross-sectional studies were evaluated with a total of 13205 cases. The sensitivity and specificity for the “Atypical and higher risk categories” considered as positive for malignancy were 97% (95% CI, 95%-99%), and 96% (95% CI, 91%-98%) respectively. The sensitivity and specificity for the “Suspicious for malignancy and higher risk categories” considered as positive for malignancy were 91% (95% CI, 85%-95%), and 99% (95% CI, 97%-100%) respectively. The sensitivity and specificity for the “Malignant” considered as positive for malignancy were 75% (95% CI, 65%-84%), and 100% (95% CI, 99%-100%) respectively. The pooled Area under the curve was 99-100% for each of the cut-offs. Conclusion This meta-analysis highlights the accuracy of the Sydney system in reporting lymph node aspirates. It exhibits the significance of the “Suspicious” and “Malignant” categories in diagnosing malignancy and of the “ Benign” category in excluding malignancy.