This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record. Numerical trial results on this page are restricted to the results posted in the ClinicalTrials.gov record; calculations added by Clinical Biostats are labelled as such.
1. Trial at a Glance
This page covers the registry results for Duloxetine for the Treatment of Chronic Pelvic Pain (NCT01451606), a randomized phase 4 study. The primary outcome is Change in Rating of Spontaneous Pelvic Pain (0 -10 Scale)..
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT01451606 |
| Phase | Phase 4 |
| Condition | Pelvis Pain Chronic |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | Double |
| Enrollment | 34 |
| Arms in the primary outcome | 2 |
| Lead sponsor | University of Maryland, Baltimore |
| Results posted | Yes |
2. Clinical Question
Population
Women with chronic pelvic pain were the intended study population. The registry record does not report further eligibility criteria or a more detailed description of the participants.
Intervention
The active intervention was duloxetine. The record describes it as a serotonergic and noradrenergic reuptake inhibitor and identifies Cymbalta as its trade name. The dose and administration schedule are not reported in the registry record.
Comparator
The comparison was a placebo pill described as looking like the active drug without active ingredients. The record identifies the study as double-masked, but does not specify which people involved in the trial were masked.
Primary question
The primary question was whether the change in spontaneous, non-evoked pelvic pain from baseline to the end of treatment differed between the duloxetine and placebo groups. Pain was rated on a 0 -10 scale, with larger changes defined in the record as better outcomes.
The clinical question concerns a specific symptom measure over the treatment period, rather than every aspect of chronic pelvic pain. The record also lists a secondary outcome concerning functional limitations due to pain, measured with a subscale of the Endometriosis Health Profile - 30. That secondary measure addresses a related but distinct aspect of participants’ experience.
The registry record does not report details such as the pain condition’s required duration, how participants were recruited, other eligibility requirements, or whether participants had particular prior treatments. The posted results therefore describe the recorded comparison and outcomes, but do not establish how broadly the findings apply to people with chronic pelvic pain beyond the study population.
3. Trial Design
This was a Phase 4, randomized, double-masked, parallel-group study comparing duloxetine with placebo. Randomization is intended to create groups whose baseline characteristics are comparable on average, while masking is intended to reduce the influence of knowledge about assigned treatment on care, assessments, or reporting. The registry record does not specify the randomization procedure, allocation concealment, or which trial roles were masked. The parallel-group model means the two assigned groups were compared over the same general study period rather than participants crossing between treatments.
The registry lists enrollment as 34. The primary outcome results are reported for 12 participants in the placebo group and 15 in the duloxetine group. The secondary outcome results use those same group counts. These reported analysis counts should not be treated as an explanation of participant flow: the registry record does not report how many participants were screened, randomized, completed treatment, or were included in each analysis, nor why the counts differ from the enrollment figure.
The study began on 2011-07-11, and the primary completion date is 2015-11-04. Its status is listed as terminated. The reason for termination, whether recruitment ended as planned, and whether the study stopped early are not reported in the registry record. The sponsor is University of Maryland, Baltimore.
The primary outcome was assessed from baseline to 8 weeks. The secondary outcome also refers to baseline and 8 weeks. The record does not report treatment dose, adherence, concurrent care, the setting, or details of visit schedules. It also does not report the planned sample size or a design justification. Enrollment and the numbers appearing in outcome results describe the record; they are not evidence by themselves about whether the study had adequate statistical precision.
4. Participant Flow and Accounting
The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.
Before assignment: In person visit to complete eligibility screening.
Overall Study
| Stage | Placebo Pill | Duloxetine |
|---|---|---|
| STARTED | 16 | 18 |
| COMPLETED | 12 | 15 |
| NOT COMPLETED | 4 | 3 |
Reasons for not completing this period:
| Reason | Placebo Pill | Duloxetine |
|---|---|---|
| Withdrawal by Subject | 4 | 3 |
5. Baseline Characteristics
The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.
| Characteristic | Unit | Placebo Pill | Duloxetine | Total |
|---|---|---|---|---|
| Participants analysed | 16 | 18 | 34 | |
| Age, Categorical: <=18 years | Participants | 0 | 0 | 0 |
| Age, Categorical: Between 18 and 65 years | Participants | 16 | 18 | 34 |
| Age, Categorical: >=65 years | Participants | 0 | 0 | 0 |
| Sex: Female, Male: Female | Participants | 16 | 18 | 34 |
| Sex: Female, Male: Male | Participants | 0 | 0 | 0 |
| Ethnicity (NIH/OMB): Hispanic or Latino | Participants | 0 | 1 | 1 |
| Ethnicity (NIH/OMB): Not Hispanic or Latino | Participants | 16 | 17 | 33 |
| Ethnicity (NIH/OMB): Unknown or Not Reported | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): American Indian or Alaska Native | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): Asian | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): Native Hawaiian or Other Pacific Islander | Participants | 0 | 1 | 1 |
| Race (NIH/OMB): Black or African American | Participants | 10 | 11 | 21 |
| Race (NIH/OMB): White | Participants | 4 | 6 | 10 |
| Race (NIH/OMB): More than one race | Participants | 2 | 0 | 2 |
| Race (NIH/OMB): Unknown or Not Reported | Participants | 0 | 0 | 0 |
| Region of Enrollment: United States | Participants | 16 | 18 | 34 |
6. Primary Endpoint
The registry lists the primary outcome as Change in Rating of Spontaneous Pelvic Pain (0 -10 Scale)., measured over Baseline and 8 weeks.
| Element | Registry entry |
|---|---|
| Result type | Median |
| Measure of spread | Inter-Quartile Range |
| Unit | units on a scale |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint was change in spontaneous pelvic pain, meaning pain that was not evoked by a stimulus. Pain intensity was assessed using a 0 -10 numerical rating scale, and the outcome was the change from the baseline period to the end of treatment at 8 weeks. The registry describes larger changes in ratings as better outcomes. It reports the group summaries as medians and inter-quartile ranges.
A change score focuses on how participants’ ratings shifted during the study rather than only their pain rating at one time point. A spontaneous-pain measure is relevant to the stated clinical question because it targets pain experienced without deliberate provocation. Using a numerical scale makes participants’ ratings analyzable as an outcome, although the values remain subjective reports and depend on how participants understand and use the scale.
The outcome description does not explain precisely how the baseline period was summarized, how repeated ratings were combined, or how the change score was calculated for each participant. Those details are not reported in the registry record. Nor does the record provide a threshold for a clinically important change. The endpoint can therefore be described as a measure of change in reported pain intensity, but the posted summaries alone do not establish how large a change would matter to participants or how the ratings related to other aspects of pelvic pain.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The primary outcome summaries show a median change of 5.0 units in the placebo group, with an inter-quartile range of 2.0 to 8.0, and a median change of 5.0 units in the duloxetine group, with an inter-quartile range of 3.0 to 6.5. The registry reports a Wilcoxon (Mann-Whitney) comparison with p = 0.52. No effect estimate or confidence interval for this comparison is reported.
The two reported medians are the same, while the inter-quartile ranges describe the middle portions of the observed distributions and are not identical. A p-value of 0.52 does not measure the size or importance of a treatment difference, and it is not the probability that the treatments are equivalent. It indicates that the reported comparison did not provide strong statistical evidence against its null hypothesis under the analysis used. Because the registry does not provide a confidence interval for the primary comparison, the precision of the difference cannot be judged directly from an interval estimate.
The primary summaries should be read as limited evidence about the comparison in the participants whose results are reported, rather than as proof that the groups were equivalent. With no interval estimate, a reader cannot use the posted primary results to identify the range of differences that remains compatible with the data. The registry also does not report an equivalence or non-inferiority objective, so the result should not be interpreted as establishing equivalence.
The secondary outcome concerns functional limitations due to pain. Its registry-reported comparison is a two-sided t-test with p = 0.84. A separate unadjusted recalculation from the posted summary statistics gives a mean difference of -8.66 units, with a 95% confidence interval from -27.65 to 10.33 and p = 0.371. That interval includes zero and spans differences in either direction. The secondary result therefore does not offer clear statistical evidence of a group difference, while also remaining imprecise enough that a range of values is compatible with the recalculation.
The primary and secondary outcomes are different measures, and their analyses use different summaries and methods. Neither result alone resolves the clinical question. In particular, non-significant p-values do not establish that there was no effect, and the secondary recalculation is not a substitute for the sponsor’s reported analysis. The registry record does not provide enough information to assess missing outcomes, analysis populations, or the context needed to judge the practical importance of any observed changes.
9. Statistical Methods Explained
What do the median and inter-quartile range describe?
The median is the middle of an ordered set of observations. It is less affected by unusually high or low values than the mean, which can make it useful when distributions are skewed or when a small study has observations far from the center. The inter-quartile range describes the spread between the lower and upper quartiles, covering the middle half of the observations. It is a measure of variability, not a confidence interval for the median and not a range containing every participant’s result.
For the primary pain outcome, the registry reports medians and inter-quartile ranges. Those summaries give a view of the center and spread in each group, but they do not show every participant’s rating or the full shape of either distribution. The registry does not report a confidence interval for the primary comparison, so uncertainty about the group contrast cannot be read from the inter-quartile ranges.
What does the Wilcoxon (Mann-Whitney) test assess?
The Wilcoxon rank-sum test, also called the Mann-Whitney test, compares observations between two independent groups using their ranks rather than relying directly on group means. It can be useful when a normal-distribution model for the outcome is not appropriate. Its result is not automatically a test of the difference between medians: interpretation depends on the distributions and the question being tested. The registry lists this method for the primary comparison and reports p = 0.52, but does not report a corresponding effect estimate or confidence interval.
A p-value describes how incompatible the observed data are with a specified null model, assuming that model and the test’s assumptions apply. It is not the probability that the null hypothesis is true, nor does it indicate the probability that a finding occurred by chance. A large p-value does not demonstrate no difference, especially when estimates are imprecise or the study has limited information.
What does the secondary confidence interval add?
The secondary outcome is summarized with group means and standard deviations, and its reported test is a two-sided t-test. A mean is the arithmetic average, while the standard deviation describes how much individual observations vary around that average. A t-test compares group means under assumptions about the observations and the analysis. The registry’s reported two-sided test has p = 0.84.
The unadjusted recalculation uses the posted group summary statistics to estimate a mean difference of -8.66 units, with a 95% confidence interval from -27.65 to 10.33 and p = 0.371. A confidence interval expresses uncertainty around an estimate under the method used: it identifies values reasonably compatible with the data and model, rather than guaranteeing that the true value lies within the particular interval. Because this interval includes zero and reaches values on either side, the recalculation does not isolate a direction of difference with confidence. It also allows for effects that could be meaningful in either direction; the registry does not state a threshold for clinical importance.
The recalculation is unadjusted and is not the sponsor’s reported analysis. It is based on posted summary statistics, which do not preserve all participant-level information. It should be read as a supplementary statistical calculation, not as a replacement for the registry-reported t-test.
How should the planning illustrations be understood?
The sample-size planning illustrations use the observed secondary effect as their starting point. Their stated assumptions are a two-sided significance level of 0.05, equal allocation between the two arms, a normal approximation, and an effect to detect defined as a stated fraction of the observed effect. The illustrations give participants per arm for 80% power and participants per arm for 90% power. For planning for 100% of the observed effect, the figures are 127 participants per arm for 80% power and 169 participants per arm for 90% power. For planning for 75% of the observed effect, they are 225 and 301 participants per arm, respectively. For planning for 50% of the observed effect, they are 505 and 676 participants per arm, respectively.
These figures are planning illustrations, not observed power and not the trial’s own design requirements. They rely on the observed effect, which may be an unstable estimate in a small study, and they do not show what the original investigators planned. The sample-size justification and the trial’s original statistical plan are not reported in the registry record. Over-dispersion, in general, means that data vary more than a chosen statistical model expects; when present, it can make uncertainty larger than a model that understates variability would suggest. Whether over-dispersion was relevant to these outcomes is not reported in the registry record.
10. Analyses Reported by the Sponsor
| Method | Estimate | 95% CI | P-value |
|---|---|---|---|
| Wilcoxon (Mann-Whitney) | not reported | 0.520 |
The registry reports the sponsor’s primary comparison as a Wilcoxon (Mann-Whitney) test with p = 0.52. It does not give an effect estimate or confidence interval for that primary comparison. The posted primary summaries are medians and inter-quartile ranges, so the available information does not support a direct reconstruction of a confidence interval for the primary contrast.
For the secondary outcome, the registry reports a two-sided t-test with p = 0.84. The unadjusted recalculation from the posted group summary statistics gives a mean difference of -8.66 units, a 95% confidence interval from -27.65 to 10.33, and p = 0.371. These values do not match the sponsor’s reported p-value. The record does not explain the difference, and the specific analysis details needed to reconcile the results are not reported in the registry record.
The discrepancy flag is false, so the recalculation is presented as a separate, simple unadjusted calculation rather than as a correction to the sponsor’s result. The sponsor’s reported analyses remain the registry’s own analyses. A recalculation from summary statistics may differ because it does not reproduce all details of the original analysis; without those details, the reason for the secondary p-value difference cannot be identified.
11. Multiplicity, Missing Data and Analysis Populations
The registry lists one primary outcome and one secondary outcome, with two outcome measures and two analyses. It does not report whether the investigators planned to adjust for multiple testing, designate a hierarchy among outcomes, or use another approach to control the overall chance of false-positive findings. Without that information, the relationship between the reported p-values and any planned multiplicity strategy cannot be assessed. A general reason multiplicity matters is that examining more outcomes or analyses creates more opportunities for an apparently unusual result, even when there is no true difference.
Missing-data methods are not reported in the registry record. The record does not specify how incomplete pain ratings or functional-limitation questionnaires were handled, whether any imputation was used, or whether analyses included all randomized participants. The analysis populations, including whether the results are based on an intention-to-treat or another population, are also not reported in the registry record. The enrollment figure and the group counts attached to results do not establish why those counts differ or what happened to participants without posted outcome data.
The record does not report interim analyses, stopping rules, or whether any outcome analyses were changed after the study began. The reason the study was terminated is not reported in the registry record. Without the original protocol or statistical analysis plan, it is not possible to determine whether the posted outcomes and analyses were prespecified or whether any changes occurred. These gaps matter because analysis choices can affect estimates, uncertainty, and how strongly results should be interpreted.
These limitations do not establish that the analyses were inappropriate; they identify information unavailable in the registry record. Readers should avoid treating the reported p-values as a complete account of the analysis plan or assuming that the available group summaries represent every randomized participant.
12. Safety Results
The registry reports serious adverse events as affected participants divided by participants at risk.
| Arm | Participants with serious adverse events | Participants at risk | Percentage |
|---|---|---|---|
| Placebo Pill | 0 | 12 | 0.0% |
| Duloxetine | 0 | 15 | 0.0% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Placebo Pill | 0 of 12 |
| Duloxetine | 0 of 15 |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 0% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Placebo Pill | 9 of 12 |
| Duloxetine | 13 of 15 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Placebo Pill | Duloxetine |
|---|---|---|---|
| Headache | Nervous system disorders | 5 of 12 | 5 of 15 |
| Nausea | Gastrointestinal disorders | 4 of 12 | 6 of 15 |
| Sleepiness | Nervous system disorders | 2 of 12 | 4 of 15 |
The registry reports zero serious adverse events in the placebo group, with 12 participants at risk, and zero serious adverse events in the duloxetine group, with 15 participants at risk. It also reports zero deaths in each group. These counts describe what was recorded during the study; they do not show that serious events are impossible or establish that the groups have identical safety profiles.
A zero event count in a study of this size can coexist with uncertainty about less common harms. The registry does not provide a confidence interval for the serious adverse event comparison, details about follow-up duration for safety, or the definitions and adjudication procedures used for events. The list of top serious-event terms is empty, consistent with no serious events being reported in the posted group summaries, but further event-level detail is not reported in the registry record.
Other adverse events are recorded for both groups, but the available safety summary does not establish their severity, timing, relationship to study treatment, or clinical importance. The serious-event counts should therefore be read narrowly as reported event totals, not as a comprehensive comparison of all possible harms.
13. What the Result Does, and Does Not, Mean
The posted primary results show the same median change in spontaneous pelvic pain in the two groups, alongside a reported Wilcoxon comparison with p = 0.52. Those data do not provide strong statistical evidence of a difference under the reported test. However, the registry does not report a primary effect estimate or confidence interval, and the result does not demonstrate that the groups are equivalent. A non-significant test is not proof of no effect.
The secondary outcome also does not offer clear evidence of a group difference. Its recalculated estimate is uncertain, and the registry’s own secondary analysis reports a different p-value. The recalculation is unadjusted and based on summary statistics, while the reason for the difference from the sponsor’s test is not reported. Both outcomes therefore leave substantial uncertainty about the size and direction of any group differences.
These results concern the participants and measurements recorded in this terminated trial. The registry record does not report a detailed participant flow, analysis populations, missing-data methods, treatment dose, or reason for termination. It also does not report a clinically important-change threshold. Those omissions limit judgments about how representative the results are, how precise the estimates are, and what the observed scale changes mean in practical terms.
The record does not justify a conclusion that duloxetine works or does not work for chronic pelvic pain. It documents a randomized comparison and its posted statistical results, but those results do not settle the clinical question. Nor do the zero serious adverse event counts establish overall safety. Interpretation should remain limited to the recorded comparisons and the uncertainty around them.
14. Why This Trial Matters Statistically
This trial illustrates a central issue in clinical statistics: a result can fail to show a clear group difference without demonstrating that the treatments are equivalent. The primary comparison has similar reported medians, but no effect estimate or confidence interval is posted. The p-value alone cannot show which sizes of difference remain plausible. That distinction is especially important when the record gives limited information about analysis populations and missing outcomes.
The contrast between a primary pain-intensity measure and a secondary functional measure also highlights that related outcomes can answer different questions. A symptom rating and a report of functional limitations are not interchangeable, and each requires appropriate interpretation. Clear outcome definitions, prespecified analysis priorities, and transparent uncertainty estimates help readers understand whether findings are consistent and how much confidence to place in them.
The secondary analysis further illustrates why statistical summaries should be interpreted in context. A recalculation from group means and standard deviations can provide an estimate and interval, but it is not necessarily the same analysis as the sponsor’s reported test. When the results differ and the analytic details are unavailable, the source of the difference cannot be resolved from the posted record alone.
Finally, planning illustrations based on an observed effect are not evidence about the study’s original design or its observed power. They can demonstrate how planning assumptions affect estimated sample requirements, but their values depend on the effect chosen and stated model. The original sample-size justification is not reported in the registry record. These distinctions make transparent reporting essential for evaluating both the strength of evidence and the limits of what a trial can answer.
15. Limitations
- The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
- Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.
Several limitations specific to this record constrain interpretation. The study is listed as terminated, but the reason for termination and whether it affected recruitment or follow-up are not reported in the registry record. Although enrollment is listed as 34, the primary and secondary outcome summaries report group counts of 12 and 15. The participant flow and reasons for the difference between enrollment and the analysis counts are not reported, so the extent or pattern of missing outcome information cannot be established.
The primary outcome is summarized with medians and inter-quartile ranges, but its between-group effect estimate and confidence interval are not posted. This makes it difficult to assess the precision of the primary comparison. For the secondary outcome, the registry’s reported p-value differs from the unadjusted recalculation based on posted summary statistics. The registry record does not give enough methodological detail to explain the difference.
The registry does not report the analysis populations, missing-data procedures, treatment dose, adherence, detailed eligibility criteria, multiplicity plan, or original statistical analysis plan. The reason for termination and any interim analyses are also not reported. These absences prevent a full assessment of prespecification, the handling of incomplete observations, and the influence of analysis choices.
Both reported group counts are limited, and the posted summaries alone cannot describe the full distribution of participant outcomes. The record also provides no threshold for a clinically important change in either outcome. These limitations mean that statistical uncertainty and clinical meaning cannot be fully assessed from the available results; they do not, by themselves, identify the cause of any limitation or imply that a particular analysis choice was made.
16. Related Tutorials
17. Related Statistical Calculators
18. Sources
- ClinicalTrials.gov: Duloxetine for the Treatment of Chronic Pelvic Pain — NCT01451606.
- Registry record last updated 2019-09-26; status last verified 2019-09.
- Results first posted 2018-01-23.
- Data retrieved from ClinicalTrials.gov on 2026-11-09.
- Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.
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19. Record Summary
NCT01451606 is a Phase 4, randomized, double-masked, parallel-group study sponsored by University of Maryland, Baltimore. It compared duloxetine with placebo for chronic pelvic pain in women. The study began on 2011-07-11, has a primary completion date of 2015-11-04, and is listed as terminated.
The primary outcome was change in spontaneous pelvic pain from baseline to 8 weeks, measured on a 0 -10 scale. The registry reports group medians and inter-quartile ranges and a Wilcoxon (Mann-Whitney) p-value of 0.52, without a primary effect estimate or confidence interval. The one secondary outcome concerns pain-related functional limitations. Its registry-reported analysis is a two-sided t-test with p = 0.84; an unadjusted recalculation gives a mean difference of -8.66 units with a 95% confidence interval from -27.65 to 10.33.
The registry reports zero serious adverse events and zero deaths in both groups. Key details about analysis populations, missing data, multiplicity, and the reason for termination are not reported in the registry record. The posted results therefore leave uncertainty about the precision and interpretation of the comparisons.