## 5 Methods
### Statistical Analyses  
Data were synthesized using meta-analytic methods. For the analysis, only the cohorts of patients thar underwent BTX-A treatment in the considered studies were included if data were available. The analysis was performed comparing baseline pain scores with the last available follow up pain scores. The effect size was calculated using standard mean differences and 95% CI. Data were statistically pooled by the standard meta-analysis approach, meaning that studies were weighted by the inverse of the sampling variance. A test of heterogeneity was applied and the I2 statistic computed. The I2 statistic indicates the proportion of total variation among the effect estimates attributed to heterogeneity rather than sampling error and has the advantage to being intrinsically independent of the number of the studies. Categorical characteristics were treated as moderators and effectiveness was compared across sub-groups formed by these moderators. Continuous characteristics were examined as covariates using random-effects (method of moments) meta-regression. We assessed publication bias using a funnel plot with a significance value on 1-tailed p values. Comprehensive Meta-Analysis V.3 (c) software (BIOSTAT, Inc. [[https://www.meta-analysis.com/](https://www.meta-analysis.com/)]([https://www.meta-analysis.com/](https://www.meta-analysis.com/)) (accessed on 10 November 2021) Comprehensive Meta-Analysis V.2 Software [computer program] was used for statistical analyses. **Supplementary Materials:** The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/toxins14010025/s1](https://www.mdpi.com/article/10.3390/toxins14010025/s1)]([https://www.mdpi.com/article/10.3390/toxins14010025/s1](https://www.mdpi.com/article/10.3390/toxins14010025/s1)), Table S1. Characteristics of the 18 included studies evaluated the efficacy of BTX-A in CPPS. Table S2. Pain score and Frequency/Nocuturia episodes for 8 included studies evaluated the efficacy of BTX-A for IC/BPS. Table S3. Pain score and Frequency/Nocuturia episodes for 3 included studies evaluated the efficacy of BTX-A for CP/PPS. Table S4. Pain scores for one included study evaluated the efficacy of BTX-A in CSP. Table S5. Pain scores in 4 included studies evaluated the efficacy of BTX-A in GPP. Table S6. Pain scores in 2 included studies evaluated the efficacy of BTX-A in MPP. Table S7. Meta-regression analysis using concomitant treatment, number of site injections and gender as moderators to test the efficacy of BTX-A injection in pain relief in IC/BPS patients. Table S8. Meta-regression analysis using symptoms duration as moderator to test the efficacy of BTX-A injection in pain relief in IC/BPS patients. Table S9. Meta-regression analysis using complications as moderator to test the efficacy of BTX-A injection in pain relief in IC/BPS patients. Table S10. Meta-regression analysis using concomitant treatment, number of site injections, symptoms duration and complication as moderators to test the efficacy of BTX-A injection in pain relief in GPP patients. Table S11. Meta-regression analysis using symptoms duration and complication as moderators to test the efficacy of BTX-A injection in pain relief in CP/PPS patients. Table S12. Meta-regression analysis using concomitant treatment and number of site injections as moderators to test the efficacy of BTX-A injection in the bladder trigone in IC/BPS patients. Table S13. Type and prevalence of adverse events/side effects of BTX-A injections in CPPS for all the 18 included studies. Figure S1. Funnel plot using standard error by Hedges' of the pooled meta-analysis of 21 selected cohorts coming from 14 included overall studies. **Author Contributions:** Conceptualization, M.A.C. and A.T.; methodology, A.P. and A.T.; software, M.A.C. ; validation, A.T. and M.A.C. ; formal analysis, M.A.C. ; investigation, A.P. and A.T.; resources, A.P., G.M., C.C. and R.O. ; data curation, A.P. ; writing--original draft preparation, A.P., A.T. and M.A.C. ; writing--review and editing, M.A.C.