Frequency‐volume chart: The minimum number of days required to obtain reliable results

AIMS: There is wide variation in the number of days necessary to maintain a diary and still furnish reliable data on which to base a sound clinical assessment. Estimates range from 1 day to 2 weeks, 7 days probably being the criterion standard. The goal of this retrospective study was to evaluate how much the 7-day period could be shortened without compromising the reliability of data. METHODS: Various lengths of frequency-volume (FV) charts (from 1 day to 6 days) were compared with the standard 7-day charts on 14 FV parameters. RESULTS: Overall results show that a 4-day dairy is nearly identical to the 7-day chart (most r > or = 0.95). Results of the 1-, 2-, and 3-day charts were frequently different statistically from the 7-day chart, whereas comparison of the 4-day chart with the 7-day chart showed no statistically significant differences. In addition, results of 4-day FV charts from a new control cohort showed no significant differences from the 7-day charts of the main cohort. CONCLUSIONS: In conclusion, our study indicates that the 4-day chart is as reliable as the 7-day chart. This reduction in the length of time, although easier for the patients, does not compromise the diagnostic value of the FV charts.