ABSTRACT & COMMENTARY
When Prolapse Become Symptomatic
By Chiara Ghetti, MD
Associate Professor, Obstetrics and Gynecology, Division of Female Pelvic Medicine and Reconstructive Surgery, Washington University School of Medicine, St. Louis, MO
Dr. Ghetti reports no financial relationships relevant to this field of study.
Prolapse occurs along a spectrum from early and asymptomatic to advanced and symptomatic. The authors define anatomic cutoffs that are likely to result in symptomatic and clinically significant prolapse.
Dietz HP, Mann KP. What is clinically relevant prolapse? An attempt at defining cutoffs for the clinical assessment of pelvic organ descent. Int Urogynecol J 2014;25:451-455.
The objective of this study was to determine the relationship between symptoms of prolapse and anatomical measurements and to define anatomical points that predict symptomatic prolapse by using receiver operator characteristic (ROC) statistics.
This was a retrospective study of archived data from 764 women evaluated for lower urinary tract symptoms and pelvic floor dysfunction. The main outcome measure was presence of prolapse symptoms defined as a “sensation of a lump or bulge” and/or a “dragging sensation in the vagina.” The degree of prolapse was quantified using three specific points of the Pelvic Organ Prolapse Quantification (POP-Q) examination, a standardized metric for evaluating pelvic organ prolapse. Specifically points Ba, C, and Bp were used. These points correspond to the lowest point (or most distal measurement) of the anterior vaginal wall, measurement of the cervix (or vaginal cuff in women who have had a hysterectomy), and the most distal measurement of the posterior wall, respectively. Logistic regression was used to model the relationship between symptoms of prolapse and POP-Q measurements of anterior, central, and posterior vaginal compartments. The authors wanted to use the POP-Q points like a diagnostic test to see if there is specific value for each point that could accurately distinguish symptomatic from asymptomatic prolapse. In order to do this, they used receiver operator characteristic (ROC) analysis.
The study included 764 patients seen during a 21-month period. The mean age was 57 years (range, 19-87). Four hundred ninety-two subjects (64%) were postmenopausal, 566 (74%) reported stress incontinence, 570 (75%) reported urge incontinence, and 407 (53%) reported symptoms of prolapse. POP-Q examination scores were available in 760 women, of which 605 (80%) had prolapse stage ≤ 2 in any compartment. POP-Q points Ba, C, and Bp were all strongly associated with symptoms of prolapse on univariate analysis. ROC curves were calculated using the complete data set for Ba, C, and Bp. To account for confounding variables, the authors repeated the analysis by only including data from women with dominant prolapse in each of the three compartments.
In the repeated analyses, 557 patients were included for Ba, 363 for C, and 486 for Bp. Improved predictions were found for all three points. The accuracy of an ROC analysis is measured by calculating the area under the curve (AUC). An area of 1 defines a perfect test, while an area of 0.5 represents a very poor test. This analysis found an AUC of 0.768 for Ba (95% CI, 0.73-0.81), 0.724 for C (95% CI, 0.67-0.78), and 0.686 for Bp (95% CI, 0.64-0.73). Cutoff values for prolapse that are likely to be symptomatic, with maximal sensitivity and specificity, were defined as follows: for Ba = -0.5 (sensitivity 69%, specificity 71%), C = -5 (sensitivity 67%, specificity 64%), Bp = -0.5 (sensitivity 63%, specificity 62%).
COMMENTARY
ROC curve analyses are often used as a tool to evaluate diagnostic tests, in particular to evaluate a test’s ability to distinguish diseased from non-diseased states.1 In theory, a test would be both highly sensitive and highly specific. The ROC curve shows the tradeoff between sensitivity and specificity of a test. Prolapse occurs along a spectrum from early and asymptomatic to advanced and symptomatic. POP-Q measurements for Ba, C, and Bp have continuous numeric values and are considered continuous outcomes. The authors wanted to use the POP-Q points like a diagnostic test to see if there is specific value for each point that could accurately distinguish symptomatic from asymptomatic prolapse.
Pelvic organ prolapse is a common condition. Women with prolapse experience a myriad of symptoms including a sensation of vaginal bulging, a vaginal lump, pelvic heaviness and/or pelvic pressure, and lower urinary tract symptoms. Women are estimated to have a 10-20% lifetime risk of surgery for prolapse, a significant risk considering women are living well into the eighth decade of life. In 2002, the Standard International Continence Society created the POP-Q system as a standardized metric to quantify prolapse.2 It consists of nine points measured in centimeters; seven defined points are measured using the hymen as a reference point. The points allow for the individual assessment of the anterior, posterior, and apical vaginal compartments as well as the measurement of length of genital hiatus and perineal body.
Some studies have found it difficult to correlate symptoms of prolapse with anatomic findings.3 By modeling the likelihood of symptoms as a function of clinical measurements in the anterior, apical, and posterior compartments by using Ba, C, and Bp measurements, respectively, the authors attempted to identify anatomic cutoff points to reliably distinguish symptomatic and asymptomatic prolapse.
The authors found fairly accurate anatomic cutoffs that are likely to result in symptomatic and clinically significant prolapse. The cutoff values are different by compartment and are Ba = -0.5, C = -5, and Bp = -0.5. For those of us not used to routinely using the POP-Q system, this translates into values that correspond to the anterior wall 0.5 cm proximal to the hymen (Ba), the cervix or vaginal cuff (C) 5 cm proximal to the hymen, and the posterior wall (Bp) 0.5 cm proximal to the hymen. At one of these anterior, apical, or posterior points, a woman is very likely to be symptomatic, and as these values worsen (or come closer to the hymen), it is more likely that a woman will become increasingly symptomatic and, hence, have more clinically significant prolapse. These cutoff values are helpful as anatomical reference points that when seen on exam may prompt us to further inquire about prolapse symptoms or help guide our counseling of women who are still asymptomatic.
References
- Pagano M, Gauvreau K. Principles of Biostatistics, 2nd edition. Pacific Grove, CA: Duxbury Press; 2000.
- Bump RC, et al. The standardization of terminology of female pelvic organ prolapse and pelvic floor dysfunction. Am J Obstet Gynecol 1996;175:10-17.
- Swift SE, et al. Correlation of symptoms with degree of pelvic organ support in a general population of women: What is pelvic organ prolapse? Am J Obstet Gynecol 2003;189:372-379.
