A method for estimating within-patient variability in maximal urinary flow rate adjusted for voided volume.


Journal Article

OBJECTIVES:To investigate whether volume adjustment can be used to reduce the within-patient variability of the maximal urinary flow rate (Qmax) without affecting the variability between patients. METHODS:We analyzed 2049 urinary flow curves of 208 men with lower urinary tract symptoms suggestive of bladder outlet obstruction and studied the relation between Qmax and voided volume (VV) in individual patients using multilevel regression analysis. RESULTS:In agreement with most previous studies, we found a hyperbolic relation between the VV and Qmax. Although hyperbolic on average, the slope of the regression line relating the VV to Qmax differed substantially across individual patients. In some patients, Qmax even tended to be lower with an increased VV. CONCLUSIONS:The reproducibility of Qmax is poor, in part because of its dependence on the VV. The current methods to adjust Qmax for VV, such as the Siroky nomogram, minimize between-patient dependency, whereas our findings emphasize the importance of within-patient variability. A common approach to adjust Qmax for VV, however, is not feasible, because the relation of Qmax to VV differs substantially across patients. The only valid, although impractical option, remains to record a large number of urinary flow curves for each patient.

Full Text

Cited Authors

  • Sonke, GS; Robertson, C; Verbeek, ALM; Witjes, WPJ; de la Rosette, JJMCH; Kiemeney, LA

Published Date

  • March 2002

Published In

Volume / Issue

  • 59 / 3

Start / End Page

  • 368 - 372

PubMed ID

  • 11880072

Pubmed Central ID

  • 11880072

Electronic International Standard Serial Number (EISSN)

  • 1527-9995

International Standard Serial Number (ISSN)

  • 0090-4295

Digital Object Identifier (DOI)

  • 10.1016/s0090-4295(01)01547-3


  • eng