Reproducibility of cystometry in overactive detrusor

Abstract

Objective: To examine the reproducibility of cystometry in the overactive detrusor.

Methods: The study sample involved 30 patients of the placebo arm in double-blind clinical trials for an overactive detrusor. They had demonstrated detrusor overactivity and underwent the second cystometry after 2-4 weeks. Nonparametric tests for paired data were used to examine the reproducibility of four variables: volume at first desire to void, volume at first involuntary contraction, cystometric capacity, and the maximum pressure of involuntary contraction. Percent change and within-subject standard deviation were calculated to assess intraindividual variability.

Results: The second test results showed a significant and systematic change for the better. Volume variables increased by 10-13% (p<0.01), involuntary contraction was not elicited in 3 cases (10%), and the maximum contraction pressure decreased by 18% in the remaining cases. Intraindividual variability was not small. Seventeen patients (57%) demonstrated > or = 25% change in one or more variables, and the 95% confidence interval of cystometric capacity, for example, was calculated as (x -57, x +57), where x is a test result. No specific patients' demographics were found related to variability.

Conclusion: Repeat cystometry in the overactive detrusor is not highly reproducible and may be subject to a systematic effect for the 'better'. Whether this is due to the placebo effect or the learning effect could not be determined.