Urodynamics (UDS) is a routine procedure used to evaluate lower urinary tract dysfunction (LUTD). However, UDS rely upon subjective interpretation and capture only a snapshot of patient symptoms and experiences, which may not reflect LUTD phenotype outside the hospital. Previously, we have demonstrated that spectral measures of bladder pressure signals derived from a novel Fast Fourier Transform (FFT)-based algorithm can identify and differentiate patients with Detrusor Overactivity (DO) throughout filling [1]. However, it is unclear how our measurements correlate with the presence, history, and severity of patient urgency symptoms. In this study, our aims were to validate our algorithm using a prospectively enrolled cohort and investigate the correlation between spectral measures and urgency symptoms as captured by the LURN SI-29, a validated patient-reported inventory of LUTD.

A total of 41 patients undergoing UDS were prospectively enrolled. The LURN SI-29 questionnaire was completed by each participant immediately before undergoing UDS. Patients with suspected urinary urgency and DO or only stress urinary incontinence (non-DO) were enrolled. Deidentified data were extracted from the clinic’s UDS system and exported for analysis. A detailed description of the FFT algorithm has previously been published [1]. Briefly, UDS were divided into equal “Early Fill” and “Late Fill” halves. After applying a custom artifact filter, FFT was applied to the vesicle pressure (Pves) and abdominal pressure (Pabd) data. Using spectra between 1-6 cycles per min, the spectra from Pabd was subtracted from Pves to estimate FFT signals specific to the bladder. Spectral power (SP), a proxy of signal amplitude, and Weighted Average Frequency (WAF), an estimate of the average signal frequency, were calculated. For LURN SI-29 analysis, we calculated the urgency subscore value (using questions 16, 17, and 18, Figure 1) as previously done by the LURN network study group [2]. Urgency subscore values greater than the upper, median, and lower quartile of the patient cohort were calculated. Similarly, individual question responses were encoded as binary outcomes, with patients reporting a score of 3 or greater. Two Sample T-test and Fisher exact test were used as appropriate to determine the association between spectral measures across filling phases and binary urgency score as well as individual question responses. Alpha value was selected at 0.05. Algorithm development and statistical analysis were performed using MATLAB (R2022a) and R (4.1.3), respectively.

Of the 42 enrolled patients, 2 withdrew, and 18 with either mixed incontinence or neither physician-diagnosed DO or SUI were excluded. 12 were classified as pure DO and 9 as non-DO. Sample size calculation to detect difference in DO diagnosis based upon a power of 85% was determined to be 7 patients per group. The mean (sd) age was 66 (13). 13 patients (62%) identified as female. Compared to Non-DO patients, the mean Late SP was significantly greater among DO patients (22 (18) vs. 4 (3), p-value = 0.006).  The mean urgency subscore was greater in DO patients compared to non-DO patients (53 (30) vs. 39 (22), p=0.2). DO patients had a greater mean score for question 16 compared to non-DO patients (3 (2) vs. 1 (1), p-value = 0.043). However, there was no difference among the remaining urgency questions (17 and 18) between groups (p<0.05). Similarly, SP during the late filling phase was significantly higher among those with a Q16 score of 3 or greater (25 (10) vs. 7(8), p-value = 0.048, Table 1].

To the best of our knowledge, this is one of the first studies to investigate the association between bladder pressure contraction spectra and severity of patient-reported symptoms. Key findings include significant associations between late SP and DO, late SP and experiencing urgency “most of the time” or “every time” over the last 7 days, as well as DO and higher mean Q16 score. It is possible that correlation of these three features are all representative of the same phenomenon: LUTD-producing pathologic bladder contraction and the sensation of urgency. However, technology for continuous outpatient bladder pressure contraction monitoring and a detailed LUTD diary are necessary to prove this hypothesis. Our findings are limited by our small patient number and exclusion of patients with mixed urgency. The direction of spectral measures was similar to our previous retrospective study. In this study, however, only Late SP was significantly different between DO and non-DO groups, unlike all spectral measures across filling phases as previously described. Future studies will aim to assess the clinical relevance of our algorithm using a larger number of patients as well as a more inclusive set of patient diagnoses.

Using a limited number of prospectively enrolled patients, an objective spectral analysis based-measure is significantly associated with severe symptoms of urinary urgency and detrusor overactivity. Further testing and validation in a larger data set are essential. However, clinical integration of this method may be useful to better assess urgency symptom severity and guide therapeutic interventions.

Ravishankar B, Vasdev RMS, Timm GW, et al. Objective Quantification of Detrusor Overactivity Using Spectral Measures of Cystometry Data [published online ahead of print, 2023 Jan 25]. Urology. 2023;S0090-4295(23)00058-4. doi:10.1016/j.urology.2023.01.012
Cella D, Smith AR, Griffith JW, et al. A new outcome measure for LUTS: Symptoms of Lower Urinary Tract Dysfunction Research Network Symptom Index-29 (LURN SI-29) questionnaire. Neurourol Urodyn. 2019;38(6):1751-1759. doi:10.1002/nau.24067

Continence 7S1 (2023) 100865
DOI: 10.1016/j.cont.2023.100865