Characteristics associated with subjective and objective measures of treatment success in women undergoing percutaneous tibial nerve stimulation vs sham for accidental bowel leakage

Introduction and hypothesis: In randomized trials both percutaneous tibial nerve stimulation (PTNS) and sham result in clinically significant improvements in accidental bowel leakage (ABL). We aimed to identify subgroups who may preferentially benefit from PTNS in women enrolled in a multicenter randomized trial. Methods: This planned secondary analysis explored factors associated with success for PTNS vs sham using various definitions: treatment responder using three cutoff points for St. Mark’s score (≥3-, ≥4-, and ≥5-point reduction); Patient Global Impression of Improvement (PGI-I) of ≥ much better; and ≥50% reduction in fecal incontinence episodes (FIEs). Backward logistic regression models were generated using elements with significance of p<0.2 for each definition and interaction terms assessed differential effects of PTNS vs sham. Results: Of 166 women randomized, 160 provided data for at least one success definition. Overall, success rates were 65% (102 out of 158), 57% (90 out of 158), and 46% (73 out of 158) for ≥3-, ≥4-, and ≥5-point St Mark’s reduction respectively; 43% (68 out of 157) for PGI-I; and 48% (70 out of 145) for ≥50% FIEs. Of those providing data for all definitions of success, 77% (109 out of 142) met one success criterion, 43% (61 out of 142) two, and 29% (41 out of 142) all three success criteria. No reliable or consistent factors were associated with improved outcomes with PTNS over sham regardless of definition. Conclusions: Despite exploring diverse success outcomes, no subgroups of women with ABL differentially responded to PTNS over sham. Success results varied widely across subjective and objective definitions. Further investigation of ABL treatment success definitions that consistently and accurately capture patient symptom burden and improvement are needed.