Predictors of efficacy of percutaneous tibial nerve stimulation for fecal incontinence: a post-hoc analysis of a randomized trial.

A recent UK multicentre, phase III trial [The CONFIDeNT Trial: Lancet 2015; 386: 1640-48], demonstrated no significant clinical benefit of percutaneous tibial nerve stimulation (PTNS) over sham stimulation; however this study did not analyse predictors of response. This study aimed to determine predictors of PTNS efficacy in adults with fecal incontinence (FI) using data from this randomized controlled trial.The study population comprised 205 patients from the CONFIDeNT Trial, with original primary outcome (≥ 50% reduction in weekly FI episodes after 12 weeks of treatment) remaining the binary denominator of success or failure. Characteristics including baseline FI symptom type, defecatory urgency and co-existent symptoms of baseline liquid stool consistency and obstructive defecation (OD) were defined a priori. Uni- and multi-variable analyses were performed to explore these factors as response covariates of response to PTNS and sham.In both uni- and multi-variable analysis, the presence of OD symptoms negatively predicted outcome in patients who received PTNS (OR 0.38; CI: 0.16-0.91; P=0.029), and positively predicted sham response (OR 3.45; CI: 1.31-9.21; P=0.012). No other tested variable affected outcome. Re-analysis of the primary outcome excluding patients with OD symptoms (n = 112) resulted in a significant clinical effect of PTNS compared to sham (48.9% vs. 18.2% response, P=0.002; multivariable OR: 4.71; CI 1.71-12.93; P=0.003).Concomitant OD symptoms negatively affected the clinical outcome of PTNS vs. sham in a major RCT. Future appropriately designed studies could further explore this observation with potential for future stratified patient selection.