title: Evaluation of repeat daily voiding measures in the National Interstitial Cystitis Data Base Study.
abstract: OBJECTIVE
  We address the importance of 3 consecutive daily frequency volume charts relative to a single day in research studies for interstitial cystitis. In addition, differences in voiding patterns between weekend days and weekdays were evaluated.
  
  
  METHODS
  Longitudinal frequency volume chart data for 305 women enrolled in the National Interstitial Cystitis Data Base Study before December 31, 1995 and meeting protocol specifications were summarized for 3 outcome measures. Longitudinal data methods designed to accommodate different within patient correlation patterns for repeat measures within and among patient contacts were implemented in a generalized estimating equation modeling framework, permitting overall testing of day and weekend effects.
  
  
  RESULTS
  Day 2 and day 3 measures were not statistically different (1% level) from day 1 for nocturnal voiding frequency and nocturia. Although statistically significant for 24-hour frequency, the mean difference of -0.36 void daily between days 1 and 3 was not likely to be clinically significant. Also, measures on weekdays were not significantly different from those on weekends for each of the 3 outcome measures.
  
  
  CONCLUSIONS
  Our results suggest that the current clinical research requirement of 3 consecutive days for frequency volume charts can be reduced to a single day. Furthermore, day selection need not be affected by weekday versus weekend considerations.
authors.affiliation: Center for Clinical Epidemiology and Biostatistics, University of Pennsylvania School of Medicine, Philadelphia 19104-6021, USA.
authors.forename: C A
authors.initials: CA
authors.lastname: Mazurick
authors.forename: J R
authors.initials: JR
authors.lastname: Landis
mesh_terms: D018856:Cystitis, Interstitial / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D014554:Urination