Clinical and Urodynamic Predictors of the Q-Tip Test in Women With Lower Urinary Tract Symptoms

Abstract

Purpose: The Q-tip test is used to measure urethral hypermobility and can predict surgical outcomes. However, certain factors may affect the reliability of this test. Our aim was to identify independent clinical and urodynamic predictors of the results of the Q-tip test.

Methods: Between January 2014 and June 2019, 176 consecutive women with lower urinary tract symptoms who underwent the Q-tip test and urodynamic studies were included in this retrospective study.

Results: Multivariable regression analysis revealed that age (regression coefficient, -0.55), point Ba (regression coefficient, 4.1), urodynamic stress incontinence (regression coefficient, 9.9), maximum flow rate (Qmax) (regression coefficient, 0.13), pressure transmission ratio (PTR) at maximum urethral pressure (MUP) (regression coefficient, -0.14), and the score on the fifth question of the Incontinence Impact Questionnaire (IIQQ5; "Has urine leakage affected your participation in social activities outside your home?"; regression coefficient, -4.1) were independent predictors of the Q-tip angle, with a constant of 87.0. The following Spearman rank correlation coefficients were found between the Q-tip angle and the following variables: age, -0.38; point Ba, 0.34; urodynamic stress incontinence, 0.32; Qmax, 0.28; PTR at MUP, -0.28; and IIQQ5, -0.23. A receiver operating characteristic curve (ROC) analysis for the prediction of urodynamic stress incontinence found that the optimum cutoff for PTR at MUP was <81%, with an area under the ROC curve of 0.70.

Conclusion: Age, point Ba, urodynamic stress incontinence, Qmax, PTR at MUP, and IIQQ5 were independent predictors of the Q-tip angle. However, none of these could be used as effective surrogates for the Q-tip test due to their lack of a sufficient correlation.

Keywords: Pelvic organ prolapse; Urinary bladder, Overactive; Urinary incontinence, Stress; Urodynamics.

Fig. 1.

(A) Comparisons of Q-tip angle between the urodynamic stress urinary incontinence (USI) and non-USI groups. Some points are not within the largest and smallest observations in the box plots, and are considered as outliers. (B) The receiver operating characteristic curves (ROC) of using Q-tip angle to predict USI. (C) Scatter fit plots of Q-tip angle and pressure transmission ratio (PTR) at maximum urethral pressure (MUP). CI, confidence interval.

Fig. 2.

(A) Comparisons of pressure transmission ratio (PTR) at maximum urethral pressure (MUP) between the urodynamic stress urinary incontinence (USI) and non-USI groups. Some points are not within the largest and smallest observations in the box plots, and are considered as outliers. (B)The receiver operating characteristic curves (ROC) of using PTR at maximum urethral pressure to predict USI.