Hypothesis / aims of study
The Neurogenic Bladder Symptom Score (NBSS) is a psychometric multidimensional tool to assess neurogenic lower urinary tract dysfunction (NLUTD). This patient-reported outcome instrument has been developed as a 24-item questionnaire that measures bladder symptoms across 3 different domains: incontinence (scored 0–29), storage and voiding (scored 0–22), and consequences (scored 0–23); there is a single general urinary QOL question scored from 0 (pleased) to 4 (unhappy). For all domains, a higher score represents a worse symptom burden or QOL.
It has been validated in different languages (Greek, Russian, Turk, Spanish, Polish, Portuguese) and various populations (multiple sclerosis, spinal cord injury, cerebral palsy).
The aim of this study was to translate, culturally adapt and validate a French-Canadian version of the NBSS for patients with multiple sclerosis (MS) or spinal cord injury (SCI).
Study design, materials and methods
In this prospective monocentric observational cross-sectional study, patients 18 years or older diagnosed with MS and SCI were recruited at our neuro-urology clinic at our rehabilitation center from November 2019 until January 2022. Standardised guidelines and well-established methods were used for translation and cross-cultural adaptation of the NBSS. Participants completed the NBSS and other measurement tools (SF-12, ICIQ, SCI-QOL). Questionnaires were filled at initial evaluation, 3-month and 6-month follow-up at in-person or phone follow-up appointments during the COVID-19 pandemic.
Internal consistency was investigated using a Cronbach's α coefficient, while test-retest evaluated reliability using an Intraclass Correlation Coefficient (ICC). Positive correlations were hypothesised for all questions. An α value of 0.70 was considered acceptable while >0.8 was considered good. Construct validity was assessed by comparing NBSS quality of life question 24 with SCI-QOL questionnaire.
Results
121 participants commenced the study, with 107 (88%) completing all questionnaires (MS (27) or SCI (80)). The total sample population (n=107) had a median age of 56 years [interquartile range (IQR) 40.5-62.6 years]. Majority of participants (n=72) were male (67%), with 35 female participants (33%). Seventy-nine patients (74%) used a wheelchair. Bladder management method was indwelling catheter in 29, intermittent catheterization (IC) in 43, voiding into a toilet in 24, condom catheter in 4 and mixed (IC+voiding) in 7.
At initial evaluation, median NBSS overall score was 24/78 (IQR 15-32.5) and subdomain scores were 9 of 29 for incontinence, 8 of 22 for storage and/or voiding, 7 of 23 for consequences and 1 of 4 for quality of life (QOL). At 6-month follow-up, median overall score was 24/78 IQR 14-31) and subdomain scores were 10/29, 6/22, 7/23 and 1/4 respectively.
The dimensions of NBSS exhibited good internal consistency, both for overall questionnaire score as shown with the Cronbach's α values in Table 1. Test-retest reliability demonstrated good stability both for overall score and for every subdomain separately at 3 months ([overall ICC of 0.66, 95%CI(0.54-0.76)], ICC of 0.58 for incontinence, 0.73 for storage symptoms and 0.58 for consequences) and 6 months ([overall ICC of 0.80, 95%CI(0.72-0.86)], ICC of 0.82 for incontinence, 0.82 for storage symptoms and 0.66 for consequences). In the construct validity, the Pearson Correlation revealed a statistically not significative (p>0.05) correlation between question number 24 of the NBSS questionnaire regarding quality of life with the SF-12 questionnaire (r= -0.12, 95%CI (-0.30 – 0.07); p=0.217 at initial evaluation; r= -0.18, 95%CI (-0.36 – 0.01); p=0.065 at 3 months.
Interpretation of results
Choosing the right measurement tool to follow-up patients with neurogenic bladder can be challenging.
Our study included a large cohort of patients with NLUTD and a follow-up of 6 months which increased the Power of our analysis and external validation. Internal consistency of the questionnaire was proven to be good (alpha value >0.70) for overall and subdomains score as demonstrated with Cronbach’s alpha analysis (see table 1).
Reliability was demonstrated as strong through test-retest assessment with intraclass coefficient (ICC) by measuring the agreement between the patients’ NBSS score at 3 months and follow-up evaluation at 6 months.
Validity was evaluated through Pearson Correlation analysis between NBSS’ question 24 and SF-12 questionnaire for quality-of-life parameters. This analysis showed a statistically non-significant result at initial evaluation and at 3 months follow-up.
These results show that NBSS questionnaire provides good internal consistency, reliability, but a limited validity as it is statistically non-significant but provides consistent information on a clinical level in a population of patients with NLUTD.