Frequency volume charts in the assessment and evaluation of treatment: how should we use them?

Frequency volume charts are an essential adjunct to both the assessment of patients at presentation and the evaluation of new treatments for filling and voiding dysfunction. Since 24 hour frequency can be altered significantly by fluid intake and insensible fluid loss. We critically evaluated the usefulness of the different parameters measured on a frequency/volume chart (FVC) to determine which provided the most reliable information. Sixty-three patients were asked to complete 2 FVCs over 3 or more days with at least one week between the two measurements. Fifty-one patients completed the diaries and the changes in mean voided volume and urinary frequency were analyzed. Eight patients had significant differences in their mean voided volume or their 24 hour frequency, 2 patients had a significant difference in both mean voided volume and 24 hour frequency. There was an excellent correlation for both the mean voided volume (r = 0.86) and the 24 hour frequency (r = 0.9). The individual variation, using repeated measures analysis, was greater for the 24 hour frequency. There is natural variation of 24 hour frequency between diaries that may invalidate apparently successful treatment outcomes. We recommend the use of the mean voided volume as part of the evaluation of new treatments in chronic voiding dysfunction and urinary incontinence.