Supplementary Material for: Neck circumference in polycystic ovary syndrome: a systematic review and bootstrapped meta-analysis with GRADE approach

Introduction: Our aim was to perform a systematic review and meta-analysis for the association of neck circumference (NC) in polycystic ovary syndrome (PCOS) patients as compared to non-PCOS controls. Methods: Primarily the PubMed/MEDLINE database, and others such as SCOPUS, Google Scholar, Cochrane Library, up to November 15, 2023 for observational studies comparing NC in PCOS versus non-PCOS women. The mean and SD values of NC and other covariates in PCOS and control groups were extracted by two independent reviewers, and the quality and risk of bias assessment was done using Newcastle–Ottawa Scale of the studies. The meta-analysis employed combined standardized mean differences (SMD) with 95% confidence intervals (CI) to compare NC between PCOS patients and controls. The heterogeneity and validity were addressed by sub-group, meta-regression, and sensitivity analyses. We conducted a Bootstrapped meta-analysis using 1000 and 10000 simulations to test the accuracy of the obtained results. The certainty of evidence was assessed by GRADE approach. Results: Our meta-analysis included 9 observational studies. The PCOS patients showed a significantly higher NC values than the non-PCOS controls (SMD 0.66, 95% CI 0.41-0.91, p<0.0001). In the bootstrap meta-analysis, the accuracy of the observed findings was proved (SMD=0.66, CI=0.42 to 0.91) for the NC outcome. No publication bias was detected in the funnel plot analysis using Begg’s and Egger’s tests. The 95% prediction interval of 0.036 to 1.28, suggest that the true outcomes of the studies are generally in the same direction as the estimated average outcome. The sensitivity analysis provided the robustness of the outcome, and no single study was overly influential on the pooled estimate. Conclusion: This meta-analysis provides accurate evidence for significantly higher NC in PCOS as compared to non-PCOS controls. There is no sufficient evidence on the diagnostic accuracy measures for NC in PCOS. Hence, further research on its diagnostic utility in PCOS is needed.