The minimum important differences for the urinary scales of the Pelvic Floor Distress Inventory and Pelvic Floor Impact Questionnaire

Am J Obstet Gynecol. 2009 May;200(5):580.e1-7. doi: 10.1016/j.ajog.2009.02.007.


Objective: We sought to estimate the minimum important difference (MID) for the Urinary Distress Inventory (UDI), UDI-stress subscale of the Pelvic Floor Distress Inventory, and Urinary Impact Questionnaire (UIQ) of the Pelvic Floor Impact Questionnaire.

Study design: We calculated MID using anchor- and distribution-based approaches from a randomized trial for nonsurgical stress incontinence treatment. Anchors included a global impression of change, incontinence episodes from a urinary diary, and the Incontinence Severity Index. Effect size and standard error of measurement were the distribution methods used.

Results: Anchor-based MIDs ranged from -22.4 to -6.4 points for the UDI, -16.5 to -4.6 points for the UDI-stress, and -17.0 to -6.5 points for the UIQ. These data were supported by 2 distribution-based estimates.

Conclusion: Reasonable estimates of MID are 11, 8, and 16 points for the UDI, UDI-stress subscale, and UIQ, respectively. Statistically significant improvements that meet these thresholds should be considered clinically important.

Trial registration: NCT00270998.

Publication types

  • Randomized Controlled Trial
  • Research Support, N.I.H., Extramural

MeSH terms

  • Adult
  • Affective Symptoms / diagnosis*
  • Female
  • Humans
  • Middle Aged
  • Pelvic Floor
  • Psychometrics / methods*
  • Quality of Life*
  • Severity of Illness Index
  • Surveys and Questionnaires*
  • Urinary Incontinence, Stress* / physiopathology
  • Urinary Incontinence, Stress* / psychology
  • Urinary Incontinence, Stress* / therapy

Associated data