Associations between subjective overactive bladder symptoms and objective parameters on bladder diary and filling cystometry

A study was conducted to assess associations between different overactive bladder (OAB) symptoms and their outcomes on bladder diary and filling cystometry parameters. We performed a retrospective cohort study in database of 6,876 Urinary Distress Inventories, 3,185 bladder diaries and 2,153 filling cystometries from women referred to our urogynecological center between 2003 and 2009. Women were dichotomized into two groups. Group I: those women without symptoms, and those with symptoms that were not bothersome. Group II: women with bothersome symptoms. Data obtained from bladder diaries were: daytime urinary frequency, nocturnal frequency, minimum voided volume, maximum voided volume, average voided volume, and incontinence episodes. From filling cystometries, volumes at first desire to void, normal desire to void, strong desire to void and maximum cystometric capacity, were extracted. Univariate and multiple linear regression analysis were performed to determine associations between OAB symptoms and bladder diary and filling cystometry measurements. After multivariate analysis the objective daytime frequency was most strongly associated with the frequency symptom (beta 0.27, p < 0.05), night time frequency with the nocturia symptom (beta 0.40, p < 0.05) and the number of incontinence episodes with the urge incontinence symptom (beta 0.37, p < 0.05). Both frequency and nocturia symptoms were significantly associated with bladder diary and cystometry filling volumes, and their effect size was the same. The urgency symptom proved to be poorly associated with objective parameters. In contrast to the frequency and nocturia symptom, the urgency symptom is poorly associated with objective parameters on bladder diary and filling cystometry. Therefore, the current practice of using frequency and incontinence episodes in outcome research of OAB trials is justified.