Achieving continence with antimuscarinic therapy for overactive bladder: effects of baseline incontinence severity and bladder diary duration.

OBJECTIVE: To examine the continence ('dryness') rate as an outcome measure of the efficacy of antimuscarinic treatment, and to explore how changes in bladder diary duration, baseline severity of urinary incontinence (UI), and study population characteristics affected this outcome.

PATIENTS AND METHODS: Urgency UI is a symptom of overactive bladder (OAB) and antimuscarinic agents are a first-line treatment for OAB symptoms; several studies have used dryness rate as an efficacy endpoint, calculated as the percentage of patients who record no UI episodes in a diary period. We performed a post hoc analysis of data from a 12-week, multicentre, randomized, double-blind, placebo-controlled trial of tolterodine extended-release (ER) in patients with symptoms of urinary frequency (> or =8 voids/24 h) and urgency UI (> or =5 episodes/week). Patients with stress UI were excluded. Diary entries from the 3-, 5-, and 7-day periods immediately preceding the baseline and the week 12 visit were used to assess the relationships between the percentage of patients reporting total dryness at week 12, diary duration (3, 5, or 7 days), baseline number of weekly UI episodes (1-6, 7-13, 14-20, > or = 21), and population analysed (intent-to-treat, ITT, or per protocol, PP). The mean changes in weekly UI episodes from baseline to week 12 are also reported by diary duration and baseline frequency of UI for patients treated with tolterodine-ER.

RESULTS: The total dryness rates decreased with increasing diary duration and greater frequency of UI at baseline. Analysis of the ITT population also showed lower dryness rates than the PP population. However, the mean reductions in weekly UI episodes for the ITT and PP populations were consistent across diary duration for each level of baseline UI frequency.

CONCLUSION: 'Dryness' varies with diary duration, baseline frequency of UI, and the population analysed. Comparisons of dryness rates between studies might lead to erroneous conclusions when these factors are not considered.