Introduction and Hypothesis <p>Progression from sacral neuromodulation (SNM) test stimulation (stage 1) to permanent implantation (stage 2) is a key decision in refractory interstitial cystitis/bladder pain syndrome (IC/BPS), but conversion rates and comparisons between percutaneous nerve evaluation (PNE) and staged tined-lead testing remain inconsistent. The primary objective of this systematic review and meta-analysis is to estimate stage 1-to -stage 2 SNM conversion in adults with refractory IC/BPS.</p> Methods <p>We registered the protocol with Prospective Register of Systematic Reviews (CRD420261286234) and conducted a Preferred Reporting Items for Systematic Reviews and Meta-Analyses-guided MEDLINE, Embase, and Web of Science review. Eligible studies included adult IC/BPS cohorts undergoing SNM test stimulation by PNE or staged tined quadripolar lead trials. Random-effects meta-analysis of proportions was performed, with subgroup analysis by test strategy and exploratory meta-regression by data source in staged studies.</p> Results <p>Seventeen studies contributed 24 cohorts (11 PNE-only, 11 staged-only, 2 mixed). Across 1087 test-phase patients, pooled conversion was 64% (95% confidence interval [CI] 55–72; I² = 72.6%). Nonmixed cohort conversion was 53% for PNE (95% CI 46–59) and 75% for staged trials (95% CI 60–86), with significant subgroup differences (<i>p</i> = 0.0058). Clinical staged cohorts converted more often than administrative/claims cohorts (79.1% vs 44.6%); administrative data source was associated with lower progression odds (odds ratio 0.21, 95% CI 0.07–0.65; <i>p</i> = 0.0153).</p> Conclusions <p>Approximately two-thirds of patients with refractory IC/BPS progressed from SNM test stimulation to permanent implantation. Staged tined-lead cohorts showed higher conversion than historical conventional PNE cohorts. Standardized success criteria and prospective, phenotype- and sex-stratified studies are needed to optimize trial strategy selection.</p>