PURPOSE: InterStim device is an U.S. Food and Drug Administration approved minimal invasive therapy for sacral neuromodulation for lower urinary tract dysfunction. Before InterStim implantation, a trial with the appropriate screening tests is required to determine patient therapy eligibility. There are two different techniques for patient screening: percutaneous nerve evaluation (PNE) test and staged test. Few studies have reported success and failure rates for each technique. However, test sensitivity and predictive values of either test have not been studied. The aim of our study was to determine the sensitivity and specificity of each test and to establish a decision algorithm for the most appropriate testing method to be used as a screening test. METHODS: This cross-sectional study was conducted from August 2009 to February 2012 and included patients with lower urinary tract dysfunction who participated in the stimulation test trial. Patients underwent PNE as the first stimulation test, while those who encountered technical difficulty during PNE or electrode migration underwent staged testing. RESULTS: A total of 213 patients, including 172 female and 41 male subjects, underwent PNE. The patients’ diagnoses included refractory overactive bladder (47.9%), nonobstructive urinary retention (29.6%), and frequency urgency syndrome (22.1%). A total of 202 patients were screened with PNE and 10 patients with staged testing. Overall sensitivity of PNE was 87.3%, and it was 90% for staged test. PNE specificity was 98.5% as compared to 92.9% for staged test. Positive and negative predictive values for PNE were 99% and 82.1% and for staged test were 90% and 92.9%, respectively. CONCLUSIONS: PNE test has high specificity and positive predictive value. We recommend PNE, a simple office-based, less expensive procedure as the first option for screening.
Cross-Sectional Studies ; Diagnosis ; Electrodes ; Female ; Humans ; Male ; Mass Screening ; Methods ; Sensitivity and Specificity* ; United States Food and Drug Administration ; Urinary Bladder, Overactive ; Urinary Retention ; Urinary Tract

PURPOSE: Sacral neuromodulation (SNM) therapy is indicated for some refractory urological conditions. The electrode lead position in sacral x-rays during routine follow-up may predict the outcome of SNM therapy. To determine whether the radiographic position of the electrode in the sacral foramen predicted the long-term outcome of SNM therapy. METHODS: This was a retrospective study of patients who underwent InterStim SNM at Toronto Western Hospital by 2 surgeons from July 2013 to March 2014. The position of electrodes in relation to the sacral bone was assessed on follow-up sacral x-rays. In the lateral view, we determined the location of the radio-opaque marker of the electrode relative to the inner surface of the sacrum (P3, D3, P2, D2, P1, D1, P0, and D0). In the anteroposterior view, the angle between a line through the spinous process shadow and the electrode was measured (0°–30°, 30°–60°, 60°–90°, >90°, or medial). Dissatisfied patients were defined as those who did not improve based on a voiding diary or those who needed salvage treatment after SNM. The primary endpoint was to determine whether the electrode lead position on sacral x-rays predicted the outcome of SNM therapy. RESULTS: A total of 69 patients (61 female and 8 male patients) were included, with a median age of 55 years. Forty-two of the patients (60.9%) had refractory overactive bladder, 21 (30.4%) suffered from chronic urinary retention, and 6 (8.7%) had lower urinary tract symptoms and chronic pelvic pain syndrome. The univariate analysis did not show any correlation between SNM response and the electrode position or angle. Dummy regression analysis using response to implantation as the dependent outcome variable did not show any significance for any of the predictors. CONCLUSIONS: Our study did not show a correlation between the long-term response to SNM and the electrode position on follow-up sacral x-rays. In this study, electrode lead position in sacral x-ray at follow-up was not correlated with the outcome of SNM therapy.
Electrodes* ; Female ; Follow-Up Studies ; Humans ; Lower Urinary Tract Symptoms ; Male ; Pelvic Pain ; Retrospective Studies ; Sacrum ; Salvage Therapy ; Surgeons ; Urinary Bladder, Overactive ; Urinary Incontinence ; Urinary Retention