Stress urinary incontinence has been increasingly recognized as a major problem in the United States, affecting up to 40% of women aged 30–50 years and 16–33% of women older than 50.1,2 The office evaluation of female stress urinary incontinence challenges physicians trying to correlate symptoms to physical findings. Evaluation of urethral hypermobility has been essential in the differential diagnosis and management of urinary incontinence. Since the 1971 observation by Crystle et al3 of a dynamic Q-tip (Unilever, London, UK) placed transurethrally, the difference between resting and Valsalva maneuver angles, “the Q-tip test,” has been widely used to assess urethral mobility.
The measurement of postvoid residual volume (PVR) with a catheter is also a common part of the examination for incontinence, and some practitioners have combined the PVR with the Q-tip test. A recent study questioning the effect of cystocele reduction on urodynamic studies reported using the catheter to measure urethral hypermobility.4 These researchers applied the standard diagnostic angle of 30 degrees for the catheter that has traditionally been used for the standard Q-tip test. We have also observed locally that some providers used the same technique; after measuring PVR, they ask the patient to perform the Valsalva maneuver with the catheter in place, thus reducing patient discomfort with repeated urethral manipulation. Upon further review with our colleagues, we noted that other providers place the Q-tip backwards inside the catheter to avoid squirting urine during Valsalva maneuver. An informal survey of providers at our institution revealed that these modifications on the Q-tip test were frequently used.
If these modifications of the Q-tip test produce statistically similar angles to the standard test, they may be preferable and therefore replace it, because they enable one transurethral manipulation to evaluate both PVR and urethral hypermobility. Although these alternative methods may offer less discomfort and shorten the examination, our systematic review of the literature (PubMed, Ovid, WebMD; keywords: “q-tip test,” “stress urinary incontinence,” “urethral hypermobility,” “cotton swab”) revealed no studies comparing these methods with the standard Q-tip test. The objective of this study was to compare the findings of two alternate methods of evaluating urethral hypermobility, the catheter alone and the catheter with Q-tip, to the standard Q-tip test.
MATERIALS AND METHODS
After the approval of the Baystate Medical Center institutional review board, 100 consecutive women from January to June 2006 referred for the evaluation of urinary incontinence and/or pelvic organ prolapse to the Division of Urogynecology and Pelvic Surgery were included in the study. Written informed consent was obtained from every study participant. The same physician examined each woman in the same way. After voiding, the patient was placed in lithotomy position, the urethral meatus was cleaned with povidone iodine solution and a 14-French polyvinyl chloride Mentor Self-Cath catheter (Coloplast, Minneapolis, MN) lubricated with lidocaine jelly, was inserted in the bladder to measure residual urinary volume. The angle of the catheter with the horizontal plane was measured at rest and with Valsalva maneuver. An angle below the horizontal was referred to as negative and those above were positive. These measurements were repeated with the wooden end of a Q-tip placed completely into the catheter. The last set of measurements was performed using the standard technique, by placing a Q-tip alone at the urethrovesical junction. A standard plastic protractor with a liquid leveling device was placed against the perineum for accurate measurement of the angles. The test was considered positive when the difference (Δ) between the resting and Valsalva maneuver angles was 30 degrees or more. The decisions to use the Δ angle, lithotomy position, and placement of the Q-tip at the urethrovesical junction were purposeful attempts to follow previously established standards.5–8 The resting, Valsalva maneuver, and Δ angles obtained during each modified technique were compared with those of the standard Q-tip test using a paired two-sample t test. With a sample size of 100 and α of 0.05, the power of the study to detect a difference of 5 degrees and 10 degrees in the Δ angle between the test methods were 94.3% and 99.9%, respectively (Minitab 12, Minitab Inc., State College, PA).
To determine the best alternative Δ angle for diagnosis using the catheter only and the catheter plus Q-tip, each angle at 30, 20, 15, 10, and 5 degrees was evaluated, and the closest match to the standard Q-tip result was selected. The angle that produced the lowest sum of errors in diagnosing both a negative and a positive Q-tip test was determined to be the “best match” angle. The McNemar test of paired proportions was used to detect statistical differences in diagnoses between the “best match” angle and the standard Q-tip angle. In addition, receiver operating characteristic (ROC) curves were reviewed for confirmation. The McNemar test and ROC curves were calculated using SPSS 14 (SPSS Inc., Chicago, IL).
This study group of 100 consecutive women had a mean age±standard deviation of 57±13 years, parity of 2.8±1.6, and body mass index of 29±6. The majority (68%) of the women were postmenopausal and one half (51%) demonstrated an anterior vaginal wall defect (type unspecified) on examination. Twenty-seven percent of the subjects had undergone prior unspecified vaginal surgery, and 14% were using hormone replacement therapy (type unspecified) at the time of the examination. The mean Δ angle for the standard Q-tip test was 51 degrees, whereas the catheter with Q-tip was 44 degrees, and catheter alone was 35 degrees. This difference was due to a significant reduction in the resting and Valsalva maneuver angles with the catheter alone, and a significant decrease only in the Valsalva maneuver angle with the catheter with Q-tip method (P<.001) (Fig. 1).
The percentage of positive tests for the standard Q-tip test (92%) was significantly different from the catheter-only method (63%, P<.001), and from the catheter with Q-tip technique (83%, P=.021) when using 30 degrees as the diagnostic angle for all methods. Comparisons of each modification to the standard Q-tip test at intervals of 5 degrees produced three different mathematical measurements of precision: percent correct, P value, and ROC curves (Table 1, Fig. 2). Combining the data from these calculations, the “best match” angles of 10 degrees for the catheter alone and 15 degrees for the catheter with Q-tip methods produce the best equivalent results at this time.
The Q-tip test has become a common instrument used by many practitioners to evaluate urethral hypermobility in patients with symptoms of urinary incontinence. However, after the discovery of this inexpensive tool, there has been little adherence to a standardized execution of the Q-tip test. After 17 years of widespread use, Karram and Bhatia5 were the first to compare different methods of performing the Q-tip test. In their study of 63 patients, they established proper placement of the Q-tip at the urethrovesical junction. They confirmed the consistency of the Q-tip test in patients with and without a symptomatic full bladder. They also agreed with other studies that indicated that an anterior wall defect was not easily correlated to extent of urethral hypermobility.6–8 Seven years later, Handa et al9 confirmed an increase in measured urethral hypermobility between 46 patients supine compared with standing, and recommended that investigators recognize patient position as a potentially confounding factor. In 2003, Pollak et al10 suggested that bladder neck mobility be assessed without reducing vaginal prolapse in their study of 26 women. These studies, collectively, provide sufficient evidence to recommend performing the Q-tip test in lithotomy position without reduction of a concurrent cystocele and by placing the Q-tip at the urethrovesical junction.
Despite these efforts to establish uniformity, a thorough literature review reveals the wide variations still used by experienced clinicians when performing this seemingly simple assessment of urethral hypermobility. Even the open discussions at national conferences are riddled with discordance about the “proper” way to perform the Q-tip test. Of significant import, there is no consistency when actually measuring the angle, be it from resting to Valsalva maneuver (as described by Crystle) or from 0 degrees to Valsalva maneuver (or cough). In addition, there seems to be no data on the variations employing the catheter for the Q-tip test.
Although it may seem gentler to use the catheter to measure the excursion angle, it is flexible and weighs more than the Q-tip. Additionally, the catheter's uniformity may allow it to slide past the urethrovesical junction, changing the fulcrum point and acting as an unintended splint. These physical properties may be evidenced in our results. The resting angle was significantly different for the catheter alone compared with the Q-tip alone. When the Q-tip was placed inside the catheter, presumably it provided more rigidity, resulting in similar resting angles between the Q-tip and the catheter with Q-tip methods. However, the added weight or splint-effect of the added Q-tip could significantly reduce the overall excursion angle, producing false-negative results. There was a statistically significant difference between the standard Q-tip test and its modifications: catheter with Q-tip and catheter alone. Of patients who had urethral hypermobility found on a positive standard Q-tip test, the catheter alone missed 29% and the catheter with Q-tip missed 9% (false negatives). Simple substitution of the Q-tip with other instruments to evaluate urethral hypermobility will significantly affect the diagnosis of this anatomic variation.
A lack of randomization of the order of the tests may be seen as a limitation of this study. Theoretically, once a patient has performed a Valsalva maneuver (or cough), the urethra may not return to the same resting angle. This would result in a significant difference between resting angles, as is seen between the Q-tip and the catheter, but not seen between the Q-tip and the catheter with Q-tip. However, the additional instrumentation required for randomization may be intolerable to the patient and difficult to justify ethically. More importantly, this study compares modifications to the “gold standard” Q-tip test. The “gold standard” must be measured under the same conditions in each patient to ensure accurate and consistent comparisons.
In our study of 100 patients, we established that 10 degrees for the catheter and 15 degrees for the catheter with Q-tip is the best match to a 30 degree angle with the Q-tip alone when used to diagnose urethral hypermobility. Nevertheless, a study evaluating the correlation of these angles and stress urinary incontinence would be appropriate, because this is the ultimate goal of the Q-tip test. A conscious effort by all clinicians to standardize practices will improve patient care and produce more predictable expectations.
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© 2007 The American College of Obstetricians and Gynecologists
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