Study design, materials and methods
A retrospective cohort study of patients who completed ≥6 PTNS sessions and underwent SNM Stage I. PTNS success was defined as >50% symptom improvement; SNM success as progression to full implant. Negative predictive value (NPV) of PTNS failure, correlation between PTNS and SNM outcomes, and subgroup analyses by urodynamic parameters (DOI vs. DO ) were performed. Univariate logistic regression explored additional predictors of SNM success.
Results
We found 22 patients, 4 (18%) achieved PTNS success and 15 (68%) achieved SNM success. The correlation between PTNS response and SNM success was negligible (p = 0.75). The NPV of PTNS failure was 33.3% (95% CI 13.3–59.0%), meaning 66.7% of PTNS failures still succeeded with SNM. In the OAB-wet subgroup (DO‐positive, n=3), SNM success was 100% regardless of PTNS response. In the OAB dry subgroup (DO‐negative, n=13), PTNS success was associated with a non‐significant higher SNM success rate (66.7% vs. 40.0%, p = 0.58).
Device reprogramming frequency in SNM implanted patient did not differ between PTNS responders and non‐responders. Univariate analysis identified detrusor overactivity (DO) as a potential predictor of SNM success ( p = 0.07).
Interpretation of results
PTNS response poorly predicts SNM success (phi=0.07). Two‑thirds of PTNS failures still achieved SNM success (NPV 33%). The wet phenotype (DO‑positive) showed universal SNM response. Thus, PTNS non‑response should not preclude an SNM trial, particularly in patients with urgency incontinence. Detrusor overactivity may be a stronger predictor than PTNS outcome.