Objective
This analysis compared 3 continuous variables as summary support loss (SL) scores with pelvic organ prolapse (POP) quantification (POPQ) ordinal stages.
Study Design
We used pooled baseline data from 1141 subjects in 3 randomized trials (CARE, n = 322; OPUS, n = 380; ATLAS, n = 439) to test 3 SL measures. The relative responsiveness was assessed using the standardized response mean of 2-year outcome data from the CARE trial.
Results
Each SL measure was strongly correlated with POPQ ordinal staging; the single most distal POPQ point had the strongest correlation. Improvements in anatomic support were weakly correlated with improvements in POP Distress Inventory (r = 0.17–0.24; P < .01 for each) but not with changes in POP Impact Questionnaire for all measures of SL or POPQ stage.
Conclusion
While continuous, single number summary measures compared favorably to ordinal POPQ staging system, the single most distal POPQ point may be preferable to POPQ ordinal stages to summarize or compare group data.
A recent US national population-based survey reported that approximately 3% of adult women have symptomatic pelvic organ prolapse (POP). As the population of the United States ages, the number of women with POP will increase with projections from 3.3 million in 2010 to 4.9 million in 2050. In 1995, the International Continence Society developed the POP Quantification (POPQ) system to standardize the anatomic assessment of POP. This system, which has been shown to be consistent across examiners, has been adopted worldwide and allowed a common language for clinicians and investigators.
The POPQ ordinal staging system, in which POP is categorized as stage 0, 1, 2, 3, or 4, quantifies the anatomic descent of the vaginal wall relative to the hymenal ring. The staging system was arbitrarily derived and there is growing sentiment that the POPQ staging system may not optimally differentiate clinically important subgroups. For example, stage 2 prolapse (leading edge within 1 cm proximal or distal to the hymen) is known to include patients who range from asymptomatic to symptomatic, yet the POPQ system does not allow for any differentiation between these groups within stage. Stage 3 is even less anatomically specific as it spans numerous centimeters beyond the points designated as stage 2. In addition, a patient may change POPQ stage with <1 cm of change in vaginal topography. A system that uses a continuous variable to stage prolapse might allow clinicians and investigators to more effectively correlate anatomy with symptoms and to more easily compare results of 1 type of surgical treatment to another.
The objective of this analysis was to compare several single numerical summary scores that are continuous variables with the established ordinal staging system. Pertinent POPQ points were used to develop equations that give numerical values to specific degrees of prolapse, thereby creating a continuum of degrees of prolapse. Using available prospectively collected data, we assessed the utility of these single continuous measures to describe pelvic organ support loss (SL). Finally, we correlated these SL measures with symptoms and condition-specific quality-of-life scores, and assessed the utility of these measures in evaluating anatomical outcomes after surgery.
Materials and Methods
We analyzed pooled baseline data from 1141 subjects in 3 randomized trials, CARE, OPUS, and ATLAS, conducted by the Pelvic Floor Disorders Network, a National Institutes of Health–sponsored multicenter network. These clinical trials used standardized tools including the POPQ, the Pelvic Floor Distress Inventory (PFDI), and the Pelvic Floor Impact Questionnaire. The CARE study enrolled women planning sacrocolpopexy for stage 2-4 prolapse without symptoms of stress incontinence and completed follow-up in 2005 ; the OPUS study enrolled stress continent women with anterior vaginal prolapse undergoing vaginal surgery and is ongoing ; and the ATLAS study enrolled women with stress incontinence and stage 0-2 vaginal support and completed follow-up in 2008. Each clinical site and the data coordinating center received institutional review board approval for these studies, and all subjects provided written informed consent.
The POPQ measurements Aa, Ba, Ap, Bp, and C have positive values when the prolapse extends beyond the hymen and negative when the particular points remain proximal to the hymen. We created 3 composite measures of SL as summary measures: SL3 (includes total vaginal length [TVL], C, Ba, and Bp), SL5 (includes TVL, C, Aa, Ba, Ap, and Bp), and SLmax (includes location of single most distal point) ( Figure ).
When there is perfect support, POPQ points Aa, Ba, Ap, and Bp equal –3; thus, the SL formulas add 3 to each of these values so that, in a situation of perfect support, the resulting measurement of SL would equal 0. In regard to C (cervix or vaginal cuff), we added this value to TVL; in a situation of perfect support, the negative C would be similar to TVL and result in a value near 0. We note that in women with a cervix in situ, perfect support may mean that negative C is not the same as TVL since the cervix is anterior and distal to the TVL measurement in the cul-de-sac. The Figure contains the equations for the 3 definitions tested in this analysis.
Each SL measure was correlated with several measures of pelvic symptoms and severity, as well as condition-specific life impact: the POPQ system stage, total scores for responses to the POP Distress Inventory (POPDI) and the POP Impact Questionnaire (POPIQ), and responses to questions 4 (“usually have a sensation of bulging or protrusion”) and 5 (“usually have a bulge or something falling out seen/felt”) of the PFDI. Pearson correlation coefficients and associated P values are reported. The relationships between POPQ stage with the SL measures POPIQ and POPDI were assessed using 1-way analysis of variance.
To assess the utility of these SL measures to describe long-term anatomical outcomes, only 2-year CARE data were used (as the ATLAS and OPUS studies only assessed 1-year outcomes). The change in each SL measure, as well as POPQ stage from baseline to 24 months, was calculated. The relative responsiveness of each measure was evaluated using the standardized response mean (SRM). SRM, a commonly used statistic of responsiveness, is defined as the mean change in score over a time period divided by the SD of individuals’ changes in scores. A higher SRM (in absolute value) indicates better responsiveness. A value of 0.5 is a cutoff for moderate responsiveness, 0.8 good responsiveness, and 1.0 excellent responsiveness. Pearson correlation coefficients were calculated for the change from baseline to 24 months in support measures and POPQ stage with corresponding changes in POPDI and POPIQ.
All reported P values were based on the 2-sided statistical tests and intended to be interpreted from a hypothesis-generating framework. The analyses were performed using software (SAS 9.1.3 for Windows; SAS Institute Inc, Cary, NC).
Results
A total of 1141 women who enrolled in 1 of the 3 trials considered in this analysis and completed at least baseline POPQ data collection are the subject of this report (CARE trial, n = 322; OPUS trial, n = 380; ATLAS trial, n = 439). Subject characteristics for this pooled group, as well as for each individual study, are shown in Table 1 . Consistent with the inclusion criteria for the studies evaluated, those enrolled in the CARE and OPUS trials had stage 2-4 prolapse while those enrolled in the ATLAS trial had stage 0-2 vaginal support. Overall, the distribution of POPQ stage for the pooled group was 4.3% stage 0, 17.9% stage 1, 29.4% stage 2, 40.5% stage 3, and 7.9% stage 4. Among subjects, 66% of subjects reported vaginal bulging as indicated by an affirmative response to PFDI question number 4 or 5 and 48% of subjects indicated that they were bothered by these symptoms moderately or quite a bit.
| Characteristic | CARE trial | OPUS trial | ATLAS trial | Total |
|---|---|---|---|---|
| n | 322 | 380 | 439 | 1141 |
| Age, y, mean (SD) | 60.9 (10.2) | 63.7 (10.0) | 49.8 (11.9) | 57.6 (12.5) |
| BMI, kg/m 2 , mean (SD) | 27.1 (4.5) | 28.1 (5.5) | 29.5 (6.8) | 28.4 (5.9) |
| Cesarean deliveries, median | 0 | 0 | 0 | 0 |
| Min-Max | 0-5 | 0-4 | 0-4 | 0-5 |
| Vaginal deliveries, median | 3 | 3 | 2 | 2 |
| Min-Max | 0-11 | 0-12 | 0-11 | 0-12 |
| Race | ||||
| White | 299/322 (92.9) | 331/380 (87.1) | 374/339 (85.2) | 1004/1141 (88.0) |
| Black | 17/322 (5.3) | 24/380 (6.3) | 44/439 (10.0) | 85/1141 (7.4) |
| Other | 6/322 (1.8) | 25/380 (6.6) | 21/439 (4.8) | 52/1141 (4.6) |
| Ethnicity | ||||
| Hispanic | 9/322 (2.8) | 52/380 (13.7) | 32/439 (7.3) | 93/1048 (8.2) |
| Prior hysterectomy | 228/271 (84.1) | 143/378 (37.8) | 108/437 (24.7) | 479/1086 (44.1) |
| Prior UI surgery | 22/322 (6.8) | 12/379 (3.2) | 27/438 (6.2) | 61/1139 (5.4) |
| Prior POP surgery | 126/322 (39.1) | 53/379 (14.0) | 15/439 (3.4) | 194/1140 (17.0) |
| Prolapse stage | ||||
| 0 | 0 (0) | 0 (0) | 49/439 (11.2) | 49/1141 (4.3) |
| 1 | 0 (0) | 0 (0) | 204/439 (46.5) | 204/1141 (17.9) |
| 2 | 44/322 (13.7) | 106/380 (27.9) | 186/439 (42.4) | 336/1141 (29.4) |
| 3 | 218/322 (67.7) | 244/380 (64.2) | 0 (0) | 462/1141 (40.5) |
| 4 | 60/322 (18.6) | 30/380 (7.9) | 0 (0) | 90/1141 (7.9) |
| PFDI question 4: “Do you usually have a sensation of bulging or protrusion from the vaginal area?” | ||||
| No | 28/315 (8.9) | 43/346 (12.4) | 346/424 (81.6) | 417/1085 (38.4) |
| Yes, how much does it bother you? | ||||
| Not at all | 10/315 (3.2) | 11/364 (3.2) | 6/424 (1.4) | 27/1085 (2.5) |
| Somewhat | 56/315 (17.8) | 67/346 (19.4) | 51/424 (12.0) | 174/1085 (16.0) |
| Moderate | 45/315 (14.3) | 66/346 (19.1) | 12/424 (2.8) | 123/1085 (11.3) |
| Quite a bit | 176/315 (55.9) | 159/346 (46.0) | 9/424 (2.1) | 344/1085 (31.7) |
| PFDI question 5: “Do you usually have a bulge that can be seen or felt in the vaginal area?” | ||||
| No | 23/315 (7.3) | 36/346 (10.4) | 388/428 (90.6) | 447/1089 (41.0) |
| Yes, how much does it bother you? | ||||
| Not at all | 8/315 (2.5) | 13/346 (3.8) | 7/428 (1.6) | 28/1089 (2.6) |
| Somewhat | 48/315 (15.2) | 63/346 (18.2) | 19/428 (4.4) | 130/1089 (11.9) |
| Moderate | 53/315 (16.8) | 58/346 (16.8) | 7/428 (1.6) | 118/1089 (10.8) |
| Quite a bit | 183/315 (58.1) | 176/346 (50.9) | 7/428 (1.6) | 366/1089 (33.6) |
| POPDI a | ||||
| Mean (SD) | 107.4 (67.3) | 59.8 (62.6) | 49.9 (48.2) | 69.8 (63.8) |
| Min-Max | 0-283.3 | 0-300 | 0-214.3 | 0-300 |
| POPIQ a | ||||
| Mean (SD) | 60.5 (77.3) | 50.9 (61.6) | 17.5 (42.7) | 40.5 (63.3) |
| Min-Max | 0-371.5 | 0-277.6 | 0-278.8 | 0-371.5 |
| SL5 b | ||||
| Mean (SD) | 27.36 (11.28) | 23.4 (10.0) | 6.71 (4.00) | 18.10 (12.60) |
| Min-Max | 7-60 | 7-58 | 0-21.5 | 0-60 |
| SL3 b | ||||
| Mean (SD) | 20.56 (9.69) | 17.09 (8.30) | 4.54 (2.61) | 13.24 (10.06) |
| Min-Max | 4-48 | 4-46 | 0-14 | 0-48 |
| SLmax b | ||||
| Mean (SD) | 3.92 (2.45) | 2.88 (2.17) | −1.46 (1.00) | 1.50 (3.05) |
| Min-Max | –1 to 12 | –1 to 10 | –3 to 1 | –3 to 12 |
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