Obstetrics & Gynecology:
Correlation of Q-Tip Values and Point Aa in Stress-Incontinent Women
Zyczynski, Halina M. MD1; Lloyd, L Keith MD2; Kenton, Kimberly MD, MS3; Menefee, Shawn MD4; Boreham, Muriel MD5; Stoddard, Anne M. ScD6; for the Urinary Incontinence Treatment Network (UITN)
From the 1Department of Obstetrics, Gynecology and Reproductive Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania; 2Division of Urology, University of Alabama at Birmingham, Birmingham, Alabama; 3Departments of Obstetrics and Gynecology and Urology, Loyola University Medical Center, Maywood, Illinois; 4Department of Obstetrics and Gynecology, Southern California Permanente Medical Group, San Diego, California; 5Department of Obstetrics and Gynecology, Baylor University Medical Center, Dallas, Texas; 6New England Research Institutes, Watertown, Massachusetts; 7National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, Maryland.
* For members of the UITN Steering Committee, see the Appendix.
Supported by grants from the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) (U01 DK58231, U01 DK58231, U01DK60379, U01 DK60380, U01 DK60401, U01 DK60397, U01 DK 58225, U01DK60395, U01 DK58234, and U01 DK58229) with support from the National Institute of Child Health and Human Development and Office of Research in Women's Health, National Institutes of Health.
Presented at the 31st Annual Society of Gynecologic Surgeons Scientific Meeting, April 3–6, 2005, Rancho Mirage, California, and the 35th Annual Meeting of the International Continence Society, August 31 to September 2, 2005, Montreal, Canada.
Corresponding author: Halina M. Zyczynski, MD, Associate Professor, Division of Urogynecology and Reconstructive Pelvic Surgery, Magee-Womens Hospital, 300 Halket Street, Pittsburgh, PA 15213; e-mail: firstname.lastname@example.org.
Financial Disclosure The authors have no potential conflicts of interest to disclose.
OBJECTIVE: To estimate the relationship between pelvic organ prolapse quantification (POP-Q) point Aa and straining Q-tip angle.
METHODS: We compared preoperative straining Q-tip angles and Aa measurements from 655 women with predominant stress incontinence and urethral hypermobility (defined as a resting or straining angle of greater than 30º) using Pearson correlations and linear regression. Point Aa is 3 cm deep to the urethral meatus in the midline of the anterior vagina and corresponds to the urethrovesical crease.
RESULTS: The median for point Aa was –1 cm (range –3 to +3 cm) and for straining Q-tip was 60º (30–130º). Twenty-nine percent of participants had an Aa at least 2 cm deep to the hymen, whereas in 69%, Aa was at or below –1 cm. The straining Q-tip angle was significantly different between these respective groups: 51.5º and 64º (P<.001). Linear regression analysis indicates that point Aa and straining Q-tip were moderately correlated (r=0.35, P<.001). As straining point Aa increased by 1 cm, Q-tip angle increased 4.6º (P<.001). Age and prior anterior vaginal or incontinence surgery had no significant effect on the correlation (P=.08 and P=.64, respectively).
CONCLUSION: Nearly a third of stress-incontinent women with urethral mobility by Q-tip test visually appeared to have a well-supported urethrovesical junction with POP-Q point Aa values of –2 cm or less. The position of the urethrovesical crease (point Aa) on POP-Q and straining angle on Q-tip test do not appear to reflect the same anatomic support and cannot be used to predict one another. No Aa value can rule out urethral hypermobility.
LEVEL OF EVIDENCE: II
Urethral mobility is common in stress-incontinent women and has been identified as a prognostic factor and a preoperative criterion for many surgical procedures.1,2 A variety of methods, ranging from chain cystourethrography to ultrasonography, have been described for quantifying urethral mobility.3–8 The most commonly reported test for quantifying urethral mobility is the Q-tip test, first described by Crystle et al in 1971.4 The Q-tip test is reliable for quantifying proximal urethral mobility when placed at the urethrovesical junction, but significant differences in straining angles are observed if the cotton swab is placed in the mid or distal urethra.11,12
Pelvic surgeons have attempted to use the pelvic organ prolapse quantification (POP-Q) system to assess urethral mobility.13 The POP-Q is an internationally accepted staging system for prolapse quantification, which consists of various well-defined points along the vagina including the anterior, apical, and posterior compartments. Point Aa (urethrovesical crease) is a midline point on the anterior vaginal wall, 3 cm proximal to the urethral meatus in a woman with no support deficits, and is thought to correspond to the urethrovesical junction. The POP-Q system, which has good intra- and interobserver reliability,14 is less invasive and uncomfortable than the Q-tip test and may be a better alternative for diagnosing urethral mobility. One retrospective study demonstrated a moderate correlation between point Aa and straining Q-tip angle.7
The aim of our study was to estimate whether POP-Q point Aa could be used as a surrogate for straining Q-tip measurements to confirm urethral hypermobility in women with stress incontinence. We sought to describe the relationship between POP-Q point Aa and maximum urethral straining angle and to determine whether this relationship is affected by pelvic organ prolapse stage in a cohort of women with stress-predominant urinary incontinence seeking surgical intervention.
MATERIALS AND METHODS
This study analyzed data collected before surgery from 655 women with stress-predominant urinary incontinence and urethral hypermobility who enrolled in the Stress Incontinence Surgical Treatment Efficacy (SISTEr) trial from February 2002 to June 2004 (trial registration information available at ClinicalTrials.gov, www.clinicaltrials.gov, NCT00064662). The enrollment criterion of urethral hypermobility was defined by a resting angle or displacement angle at maximum Valsalva effort of more than 30º from the horizontal plane. This randomized trial evaluated the effect of two commonly performed procedures for stress urinary incontinence, the Burch colposuspension and the autologous rectus fascial sling. The methods and primary outcomes measures of the SISTEr trial have previously been reported.15 The study was conducted by the Urinary Incontinence Treatment Network, a cooperative agreement network sponsored by the National Institute of Diabetes and Digestive and Kidney Diseases. Each clinical site and the biostatistical coordinating center obtained approval for this trial from their respective institutional review boards. All enrolled subjects provided written informed consent.
A complete physical examination and patient history were taken before surgery. The pelvic examination was conducted with the women in lithotomy position. Urethral mobility was measured in a standardized manner with the Q-tip test, using a goniometer. Examiners inserted a sterile, lubricated cotton or Dacron swab into the bladder through the urethra and then withdrew the swab until they sensed tension, which was presumed to be the urethrovesical junction. A goniometer with 5º increments measured the angle of the swab relative to the horizontal plane at rest and again when the patient was instructed to maximally strain. Uterine and vaginal support was assessed by the POP-Q examination, which was performed according to the guidelines established by the International Continence Society.13 All Urinary Incontinence Treatment Network examiners were required to view the videotape demonstrating the POP-Q examination produced by Duke University Medical Center (“Pelvic Organ Prolapse Quantification Examination”). Point Aa, which is thought to represent the location of the urethrovesical junction, was measured relative to the hymen in the midline of the anterior vagina with a centimeter ruler while the subject was straining maximally. Only certified examiners who were study surgeons and research coordinators obtained preoperative baseline POP-Q and Q-tip data. We did not designate an order for data collection.
Descriptive statistics were computed on patient characteristics thought to influence Aa, Q-tip values, or their association. These included age, body mass index (BMI), race and ethnicity, parity, and a history of anterior vaginal or incontinence surgery. Advancing age is associated with urogenital atrophy, which might differentially affect Aa and Q-tip angle values. Weight loss in obese incontinent women has been associated with improvement in stress urinary incontinence symptoms. We explored whether obesity (BMI more than 30 kg/m2) influenced the relationship between anterior vaginal wall descent and urethral mobility. Likewise, pregnancy and anterior vaginal wall or incontinence surgery can alter the topography of the anterior vaginal wall, either with vaginal skin attenuation or resection and plication. We sought to explore whether these experiences affected the relationship between Aa and Q-tip. We then divided women into two groups based on the position of POP-Q point Aa using a clinically relevant anatomic cutoff for hypermobility. Those with a Point Aa 2- or 3-cm deep to the hymen (–2 cm or less) were considered to have a “well supported” distal anterior vaginal wall, and those with an Aa that descended to within 1 cm of the hymen or more distal (–1 to +3 cm) were considered to be “poorly supported.” Our decision to dichotomize urethral support in this manner is consistent with the observation of Cogan et al7 and Noblett et al,16 who found that 95% and 100% of their patients with urethral mobility of more than 30º had an Aa point of –1 or greater. This cutoff at –1 cm has also been found to correspond to a threshold of symptoms related to prolapse.17
We performed Pearson correlation and linear regression analysis of Q-tip straining on point Aa. To control for potential confounders or effect modifiers, we added the potential covariates to the linear regression models. All analyses were carried out with the personal computer version of SAS 9.0 (SAS Institute Inc, Cary, NC).
Relevant demographic, medical history, and physical examination characteristics of the 655 women who participated in the SISTEr trial are listed in Table 1. We compared POP-Q point Aa with the straining Q-tip angle throughout their range of values. Figure 1 shows the distribution of straining Q-tip angle for women at each value of point Aa. Straining angle tended to increase with increasing value of Aa (or as Aa becomes more prolapsed). In the linear regression model, as point Aa increases by 1 cm, Q-tip straining angle increases 4.6º on average (r=0.35, P<.001). Body mass index was significantly associated with straining angle, but controlling for BMI did not change the relationship between point Aa and Q-tip straining angle. Prior anterior vaginal wall or incontinence surgery had no significant effect on the correlation between Aa and straining Q-tip angle (P=.64). There was a weak effect with age (P=.08), but when other variables were controlled, age was no longer significant. The number of pregnancies and race/ethnicity were not associated with Q-tip straining angle when point Aa was controlled.
When subjects were divided into groups based on distal anterior vaginal wall support, the mean straining Q-tip values for the 190 (29%) subjects judged to have a “well supported” distal anterior vaginal wall (Aa –2 cm or less) was 51.5±14.6º compared with 64±18.6º in the 454 (69%) women with a “poorly supported” distal anterior vaginal wall (Aa –1 cm or greater) (P<.001).
The overall stage of prolapse in the POP-Q examination is determined by the lowest presenting part of the vagina or cervix (points Ba, Bp, or C). To explore the influence (potential distortion effect) that “overall” stage of prolapse had on the relationship of Aa and straining Q-tip angle, we performed a (linear, multivariable) regression analysis with POP-Q stage held constant. In this analysis, POP-Q stage was significantly associated with Q-tip straining angle (P=.01), such that women in stage II had the greatest straining angle compared with women in the other two stage groups (0/I and III/IV), but the relationship between point Aa and straining angle was essentially unchanged. As point Aa increased by 1 cm, Q-tip straining angle increased 4.3º on average, when stage of prolapse was held constant (P<.001). When we restricted the analysis to those women with point Aa between –3 and +1 (n=608), the strength of the association between point Aa and straining angle was similar. In this subgroup, as point Aa increases by 1 cm, straining angle increased 5.7 degrees (r=0.35, P=.001).
Nearly a third of stress-incontinent women with urethral mobility by Q-tip test visually appeared to have a well-supported urethrovesical junction with Aa values of –2 cm or less in this large prospective study. The position of the anterior vaginal wall only weakly correlated with the maximum Q-tip straining angle. The position of the urethrovesical crease (point Aa) on POP-Q and straining angle on Q-tip test do not appear to reflect the same anatomic support and cannot be used to predict one another. No Aa value can rule out urethral hypermobility.
Our findings are consistent with others who attempted to identify a “cutoff” value for point Aa, which could reliably diagnose urethral hypermobility. Montella et al18 found that point Aa values less than +2 were neither sensitive nor specific for predicting urethral hypermobility in 111 women with prolapse or urinary incontinence or both. Similarly, Cogan et al7 found that 95% of patients with stage II or greater prolapse met criteria for hypermobility with straining angles of more than 30º. However, small numbers of women with stage 0/I prolapse limited the conclusions. In a study of 134 consecutive women referred for an urogynecology evaluation, women with stage 0 prolapse met criteria for urethral hypermobility 6% of the time, stage I prolapse 91%, and stage II or greater prolapse 100%. When point Aa was stage I or less, point Aa had a positive predictive value of 82% for urethral hypermobility (Q-tip angle of 30º or more) and a negative predictive value of 94%. The authors concluded that women with stage 0 or I prolapse required a Q-tip test to assess urethral mobility whereas those in higher stages did not.16 Our study findings reinforce this advisory.
Urethral mobility, as defined by the Q-tip test, is considered a selection criterion and prognostic factor for incontinence procedures such as the retropubic urethropexy and the rectus fascial sling. The optimal method for determining urethral mobility remains unclear because both Q-tip and POP-Q have intrinsic flaws. Both measurements are influenced by straining effort as well as the accuracy of the examiner's gross visual measurements. Assessing urethral mobility by POP-Q has the advantage of avoiding discomfort from urethral probing and the variability of correct swab positioning at the bladder neck. Additionally, interobserver and intraobserver reliability of the POP-Q examination components has been established.14 However, anterior vaginal wall morphology is influenced by numerous factors such as muscularis hypertrophy, rugae, obstetric lacerations, surgical distortion, and urethral diverticula. Caputo and Benson8 reported on the use of perineal ultrasonography as an alternative to more accurately measure proximal urethral mobility, but access to ultrasonography in the ambulatory setting and its associated expense has limited its utility.
All of the women enrolled in the SISTEr trial had urethral hypermobility by Q-tip; therefore, we are unable to determine an Aa value that assures the presence of urethral hypermobility and circumvents the need for a Q-tip test. Regrettably, we did not standardize our method for obtaining Q-tip straining angles in women with advanced (stage III/IV) prolapse. Examiners variably reduced and maintained support of the uterus and vaginal walls during the Q-tip angle measurements so that the prolapsing vaginal wall or cervix did not deflect the swab. This variability in technique may explain the wider range of Q-tip values and the lack of correlation between Q-tip angle and positive Aa values in women with advanced prolapse. We recommend that a standardized technique for prolapse reduction be used by future investigators because reduction method and loss of apical support may influence urethral mobility.
Our findings suggest that clinicians who visually ascertain urethral mobility by watching descent of the distal anterior vagina during Valsalva efforts may underestimate the presence of hypermobility. The Urinary Incontinence Treatment Network is currently conducting a randomized trial comparing the outcomes after transobturator and retropubic polypropylene mesh midurethral slings. Preoperative urethral mobility will be analyzed as a prognostic variable in the continence outcomes of both procedures. Until clinical trials specifically define the prognostic value of point Aa in incontinent women undergoing surgery, clinicians should not use this anatomic landmark as a selection criterion for procedures.
This study confirms that, although there is a positive correlation between the POP-Q measurement point Aa and the Q-tip straining angle, point Aa of –1 cm or less should not be used as a surrogate for good urethral support and does not predict the absence of urethral hypermobility.
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Urinary Incontinence Treatment Network Steering Committee
William Steers, MD, Chair (University of Virginia, Charlottesville, Virginia); Ananias C. Diokno, MD (William Beaumont Hospital, Royal Oak, Michigan); Salil Khandwala MD, Veronica Mallett, MD (Oakwood Hospital, Dearborn, Michigan; U01 DK58231); Linda Brubaker, MD, Mary Pat FitzGerald, MD (Loyola University Medical Center, Maywood, Illinois; U01DK60379); Holly E. Richter, PhD, MD, L. Keith Lloyd, MD (University of Alabama, Birmingham, Alabama; U01 DK60380); Michael Albo, MD, Charles Nager, MD (University of California, San Diego, California; U01 DK60401); Toby Chai, MD, Harry W. Johnson, MD (University of Maryland, Baltimore, Maryland; U01 DK60397); Halina M. Zyczynski, MD, Wendy Leng, MD (University of Pittsburgh, Pittsburgh, Pennsylvania; U01 DK 58225); Philippe Zimmern, MD, Gary Lemack, MD (University of Texas Southwestern, Dallas, Texas; U01DK60395); Stephen Kraus, MD, Thomas Rozanski, MD (University of Texas Health Sciences Center, San Antonio, Texas; U01 DK58234); Peggy Norton, MD, Lindsey Kerr, MD (University of Utah, Salt Lake City, Utah; U01 DK60393); Sharon Tennstedt, PhD, Anne Stoddard, ScD (New England Research Institutes, Watertown, Massachusetts; U01DK58229); John W. Kusek, PhD, Leroy M. Nyberg, MD, PhD, Debuene Chang, MD (National Institute of Diabetes and Digestive and Kidney Diseases); Anne M. Weber, MD (National Institute of Child Health and Human Development). Cited Here...
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