Correlations of mean voided volume with other parameters of overactive bladder syndrome

Abstract

Mean voided volume (MVV) is a non-invasive indicator of urinary bladder capacity and frequently used as secondary or even primary endpoint in clinical studies of bladder function, particularly in the context of overactive bladder syndrome. We have analyzed previously reported results from two large, non-interventional studies (n = 1335 and 745 patients with overactive bladder syndrome treated with 30–45 mg propiverine ER) to address two questions: How does MVV relate to other typically used parameters of overactive bladder syndrome (primary aim)? Is MVV a normally distributed variable (secondary aim)? We found that distribution of MVV at baseline and after treatment exhibits a skewed distribution and deviates from a normal distribution, albeit not to a major extent. Basal MVV was weakly to moderately inversely correlated to numbers of urgency, incontinence and nocturia episodes (Spearman’s correlation coefficient 0.2224–0.2960) and somewhat stronger but still only moderately to micturition frequency (0.3296–0.3505). Associations of similar strength were found for absolute and % treatment-associated changes of MVV. MVV was not associated with age and only inconsistently with gender. We conclude that MVV should not be treated as a normally distributed variable and propose that at least partly different (patho)physiological factors may regulate MVV as compared to urgency, incontinence, frequency and nocturia. This should be considered in the choice of primary endpoint in clinical studies.

Keywords

• Overactive bladder syndrome
• Mean voided volume
• Propiverine
• Non-interventional study
• Normality testing
• Correlation analysis