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 Pregabalin for the Treatment of Vulvodynia (NCT00853229), a randomized phase 2 study. The primary outcome is Reduction in Average Pain Over the Last 7 Days of Each Arm Using an 11-point Scale (0-10).
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT00853229 |
| Phase | Phase 2 |
| Condition | Vulvodynia, Vulvar Vestibulitis |
| Allocation | Randomized |
| Design model | Crossover |
| Masking | Triple |
| Enrollment | 16 |
| Arms in the primary outcome | n/a |
| Lead sponsor | The Cleveland Clinic |
| Results posted | Yes |
2. Clinical Question
Population
The study concerned women with vulvodynia, including the listed condition vulvar vestibulitis. The registry record gives an enrollment of 16, but the primary outcome description says outcomes were not assessed after early discontinuation because of poor recruitment. It does not report how many participants completed either treatment period or contributed outcome measurements.
Intervention
The intervention was pregabalin, identified in the record as Lyrica in the official title. The study used a crossover design, so the two sequence descriptions place pregabalin and placebo in different orders. The registry record does not report the dose or other details of how the medication was administered.
Comparator
The comparator was placebo. One sequence was pregabalin followed by placebo, and the other was placebo followed by pregabalin. The record does not report the duration of each treatment period beyond the primary outcome timeframe, or whether a washout period separated treatments.
Primary question
The intended primary question was whether pain decreased after four weeks of treatment, comparing the average pain over the last 7 days of each arm on an 11-point scale from 0 to 10. A responder was defined as a participant reporting at least a 50% reduction in pain. The trial was terminated before the designated follow-up interval, and the primary measure was not assessed. Consequently, the registry record does not contain an estimate of the treatment contrast or evidence answering the intended efficacy question.
3. Trial Design
The registry identifies this as a randomized, triple-masked, placebo-controlled crossover study, listed as Phase 2. Its official title also describes it as randomized, double-blinded, and placebo-controlled. The sponsor was The Cleveland Clinic. The recorded enrollment was 16. These details describe the planned trial structure; they do not establish how many participants completed treatment or were included in an outcome analysis.
In a crossover trial, participants are assigned to treatment sequences and can receive both the intervention and the comparator at different times. Here, the registry lists a pregabalin/placebo sequence and a placebo/pregabalin sequence. This setup can allow comparisons within participants, while randomizing the order helps determine which treatment comes first. These are general features of crossover designs, not a description of an analysis performed in this study.
The registry records a study start of 2009-02 and a primary completion date of 2013-04. Its status is TERMINATED. The primary outcome description states that the study ended early because of poor recruitment, before the designated follow-up interval, and that no outcomes data were collected. Thus, the enrollment entry should not be read as evidence that the planned outcome follow-up was completed.
The record does not specify the medication dose, treatment-period schedule, washout procedures, allocation ratio, or the people covered by triple masking. It also does not report a statistical analysis plan. Those details cannot be inferred from the sequence labels or the masking designation.
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.
Phase 1: Initial Intervention
| Stage | Pregabalin First 4 Weeks | Placebo First 4 Weeks |
|---|---|---|
| STARTED | 8 | 8 |
| COMPLETED | 0 | 0 |
| NOT COMPLETED | 8 | 8 |
Reasons for not completing this period:
| Reason | Pregabalin First 4 Weeks | Placebo First 4 Weeks |
|---|---|---|
| Early study termination, poor enrollment | 8 | 8 |
Phase 2: Cross Over
| Stage | Pregabalin First 4 Weeks | Placebo First 4 Weeks |
|---|---|---|
| STARTED | 0 | 0 |
| COMPLETED | 0 | 0 |
| NOT COMPLETED | 0 | 0 |
Analysis population for the primary outcome, as defined in the registry: Outcomes measure not assessed due to early discontinuation because of poor recruitment. As such, the study was terminated prior to the designated follow up interval. Therefore, no outcomes data was collected.
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.
Population: No study analysis completed due to early termination due to poor enrollment
| Characteristic | Unit | Pregabalin First 4 Weeks | Placebo First 4 Weeks | Total |
|---|---|---|---|---|
| Participants analysed | 8 | 8 | 16 | |
| Age, Continuous | years | 35.0 (SD 8.9) | 36.3 (SD 13.1) | 35.6 (SD 11.0) |
| Sex: Female, Male: Female | Participants | 8 | 8 | 16 |
| Sex: Female, Male: Male | Participants | 0 | 0 | 0 |
| Region of Enrollment: United States | participants | 8 | 8 | 16 |
6. Primary Endpoint
The registry lists the primary outcome as Reduction in Average Pain Over the Last 7 Days of Each Arm Using an 11-point Scale (0-10), measured over 4 weeks.
| Element | Registry entry |
|---|---|
| Result type | N/A |
| Measure of spread | not applicable |
| Unit | not stated |
| Endpoint classification | not reduced to a single comparison |
The intended primary endpoint was reduction in average pain over the last 7 days of each treatment arm, assessed at four weeks using an 11-point numerical rating scale. The scale runs from 0 through 10: 0 means no pain, and 10 means the worst imaginable pain. The record also defines a responder as a participant noting at least a 50% reduction in pain on this scale.
Pain ratings provide a direct way to represent a participant’s reported pain intensity. Looking at an average over the last 7 days of an arm is intended to characterize pain near the end of that treatment period, rather than relying on a single momentary rating. The responder definition describes a separate way to classify change according to a stated threshold. These are general interpretations of the measurement choices; they do not indicate that either measure was observed in this trial.
The primary outcome description explicitly says the measure was not assessed because the study was discontinued early after poor recruitment and did not reach the designated follow-up interval. No participant-level pain results, summary statistics, treatment comparison, or responder counts are reported. Therefore, the endpoint can be described as planned, but its value and the contrast between pregabalin and placebo cannot be estimated from the registry record.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The main statistical finding is the absence of primary outcome data. Although the registry describes a planned comparison of pain reduction after four weeks, it states that the measure was not assessed and that no outcomes data were collected because of early discontinuation after poor recruitment. There is therefore no reported treatment effect, uncertainty interval, or test of the primary question. The record does not support a conclusion about whether pain differed between pregabalin and placebo.
The enrollment entry is 16, and the two adverse-event groups each list 8 participants at risk. Those entries do not substitute for pain measurements. They also do not establish that all enrolled participants completed both sequence periods. The registry does not report completion or follow-up counts for the primary endpoint.
Because the primary outcome was not collected, the responder definition cannot be applied to observed participant data. No responder counts or percentages are reported. The secondary outcome listed in the record concerns anxiety and depression based on the Kessler Psychological Distress Scale (K10), but the record does not report results for it either. It lists 2 outcome measures and 0 analyses; there is no posted outcome analysis to interpret.
The adverse-event entries are a distinct part of the record. Each sequence group lists 0 participants affected by serious adverse events among 8 at risk, and 0 affected by other adverse events among 8 at risk. These are the reported counts for those categories; they do not provide evidence about pain reduction or establish that no unrecorded events occurred. Death counts are not reported in the registry record.
General statistical interpretation depends on both the estimated effect and its precision. A confidence interval, for example, describes a range of values compatible with the data under the specified method. No such interval is reported for the primary outcome, because no primary outcome data were collected. A p-value or an estimate cannot be recovered from the design description alone. The registry record therefore documents the study’s intended question and early termination, but does not provide an efficacy result.
The reported reason for termination, poor recruitment, is relevant to feasibility and the lack of follow-up data. It is not a finding about the effect of pregabalin. The appropriate reading is limited: the planned endpoint was not assessed, so the record leaves the primary clinical question unanswered.
9. Statistical Methods Explained
Randomization assigns participants to study sequences by chance. In this trial, the registry describes two orders: pregabalin followed by placebo, and placebo followed by pregabalin. Randomization can help prevent systematic differences in treatment order from being chosen by investigators or participants. The record does not report the specific randomization procedure or the number assigned to each sequence beyond the adverse-event group entries.
What does crossover mean?
General explanation: a crossover design gives participants more than one treatment in sequence. If outcomes are measured in each treatment period, a comparison can use the fact that the same participant experienced both conditions. This can account for stable differences between participants, but valid interpretation also depends on treatment order, period effects, and whether effects of one treatment persist into another period. The registry record does not report a washout procedure, period-specific outcome data, or an analysis addressing these issues. Since the primary outcome was not assessed, no within-participant treatment comparison is available.
What does masking describe?
The record identifies the trial as triple-masked, while its official title calls it double-blinded. Masking is intended to limit the influence of treatment knowledge on participant experience, care, or outcome assessment. The record does not say which roles were masked, or explain the difference between the masking designation and wording in the official title. It is therefore possible to report the registry’s labels, but not to specify who was unaware of the assigned treatment.
What would an effect estimate mean?
General explanation: an effect estimate summarizes the observed contrast between treatment conditions for a defined outcome. In a crossover study, that contrast may be based on measurements from both periods, with the statistical method accounting for the paired structure. Its interpretation depends on the outcome definition and analysis population. Here, the primary outcome was not collected, so there is no estimate to interpret. The registry also reports 0 analyses, and no primary-outcome model or test is reported in the registry record.
How should uncertainty be understood?
General explanation: a confidence interval communicates the precision of an estimated effect, showing a range of values compatible with the observed data under the chosen method. A narrow interval generally indicates more precision than a wide interval, while an interval alone does not establish clinical importance. A p-value, when reported, relates the observed data to a specified statistical model and null hypothesis; it is not a measure of the size or importance of an effect. Neither a confidence interval nor a p-value for the primary outcome is reported in the registry record. With no collected outcome data, these quantities cannot be interpreted as trial findings.
Why does over-dispersion matter in general?
General explanation: over-dispersion occurs when the variability in data is greater than a statistical model assumes. If a model does not account for that extra variability, uncertainty may be understated. This concept can matter for outcomes represented as counts or rates, but the registry does not report a primary-outcome analysis or a model for this trial. It would be inappropriate to claim that over-dispersion was present or that a particular method was used.
What can the planned responder definition tell us?
The record defines a responder as someone noting at least a 50% reduction in pain on the 0-to-10 scale. A threshold can make an outcome easier to interpret as a category, but it discards some information about the amount of change when compared with retaining the original scale. This is a general statistical consideration, not an observed result from this study. The record gives no responder totals, so neither the number meeting the threshold nor the difference between sequences is known.
The registry describes a Phase 2 trial with randomization and masking, but the stated design alone does not disclose the statistical methods that would have been used to analyze a completed study. The analysis plan, treatment of missing measurements, approach to period effects, and approach to multiplicity are not reported in the registry record. No method should be attributed to the investigators without that information.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists a primary pain outcome and a secondary outcome concerning anxiety and depression based on the Kessler Psychological Distress Scale (K10). It records 2 outcome measures and 0 analyses. Because no outcome data were collected, there are no reported tests or estimates across these measures to interpret. A multiplicity adjustment or other strategy for handling several outcome comparisons is not reported in the registry record.
Multiplicity is a general statistical concern when many hypotheses are tested: the chance of at least one apparently notable result can rise as the number of tests increases. Whether and how to address that concern depends on the planned analysis and the role of each endpoint. The registry does not report a testing hierarchy, adjustment procedure, or analysis plan, so none can be assumed.
Missingness is more than an ordinary set of unrecorded individual measurements in this case. The primary outcome description says the study ended before the designated follow-up interval and no outcomes data were collected. The record does not report participant-level reasons for missing observations, follow-up completion, imputation, or sensitivity analyses. It is not possible to determine how missing data would have been handled in an analysis.
The record also does not define an analysis population, such as whether an intended analysis would include all randomized participants or only participants completing both periods. Although enrollment is listed as 16, that does not identify an outcome-analysis population. Without outcome measurements and a reported analysis plan, neither missing-data assumptions nor the population used for an efficacy estimate can be evaluated.
11. 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 |
|---|---|---|---|
| Pregabalin/Placebo | 0 | 8 | 0.0% |
| Placebo/Pregabalin | 0 | 8 | 0.0% |
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 |
|---|---|
| Pregabalin/Placebo | 0 of 8 |
| Placebo/Pregabalin | 0 of 8 |
The registry reports serious adverse-event figures separately for the Pregabalin/Placebo and Placebo/Pregabalin sequence groups. Each group lists 8 participants at risk and 0 participants affected by serious adverse events. The other-adverse-event entries also list 8 at risk and 0 affected in each group. These are the counts recorded for the listed groups and categories.
A zero count means that no affected participants were recorded in that category in the registry entry; it does not establish that an event is impossible or that an unreported event did not occur. These figures should be read as descriptive safety entries, not as a comparison demonstrating a difference between treatments. In a crossover design, sequence-group counts also do not by themselves show how events were distributed by treatment period.
Deaths are not reported in the registry record. The record does not provide further details about event definitions, timing, severity beyond the serious/non-serious categories, or attribution to treatment. The reported adverse-event counts therefore should not be expanded into claims about overall safety or used to infer an unreported treatment-specific risk.
12. What the Result Does, and Does Not, Mean
The record establishes that a randomized, triple-masked, placebo-controlled crossover study of pregabalin for vulvodynia was registered, with two treatment sequences and an intended pain endpoint. It also documents that the study was terminated after poor recruitment before the designated follow-up interval. The primary outcome was not assessed, and the record states that no outcomes data were collected.
Those details do not show that pregabalin reduced pain, and they do not show that it failed to reduce pain. There is no observed primary treatment contrast on which to base either conclusion. The responder threshold was specified, but the record does not report whether any participants met it. Likewise, the secondary K10 outcome is listed without a reported result.
The adverse-event entries report 0 affected participants for serious and other adverse events in each sequence group, with 8 at risk in each. These counts describe only the listed registry categories. They do not supply evidence about the primary efficacy outcome, and deaths are not reported in the registry record.
General statistical principle: an inconclusive record caused by absent outcomes is different from a completed analysis that estimates an effect near zero. In the former situation, there is no estimate and no precision measure to assess. The absence of a reported result must not be interpreted as evidence of no effect. Nor can a planned sample-size calculation or a design label substitute for observed outcome data.
The most defensible conclusion is that the registry documents the trial’s intended comparison and its early termination, but does not answer the clinical question posed by the primary endpoint. The findings are therefore limited to trial status, design information, and the adverse-event counts that were recorded.
13. Why This Trial Matters Statistically
This trial matters statistically because it illustrates the distinction between a planned study and an informative outcome analysis. Randomization, masking, a placebo comparator, and a crossover structure describe ways a trial may be designed to reduce bias or improve comparisons. They cannot produce an estimate when the primary measure was never collected.
The registry also makes the consequences of early termination explicit: poor recruitment led to discontinuation before the designated follow-up interval, and no outcomes data were collected. That account helps readers distinguish an absent efficacy result from a reported estimate with substantial uncertainty. Without outcome data, there is no way to determine the direction, size, or precision of a treatment contrast.
General lesson: design labels are not a substitute for examining what was measured and analyzed. In crossover studies, treatment order and period structure are important to interpretation; these details matter only when usable period-specific outcomes and an appropriate analysis are available. The registry does not report those data or an analysis plan.
The record further shows why safety counts and efficacy results should be kept separate. The listed adverse-event counts are descriptive entries, while the primary pain endpoint and the secondary psychological distress measure have no reported results. Each type of information answers a different question and cannot stand in for another.
For clinical researchers and biostatisticians, the key point is methodological restraint: interpret the recorded details, identify the missing information, and do not turn non-collection into a negative result. This record supports an account of the intended design and why the endpoint is unavailable, not an estimate of treatment effect.
14. 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.
The central limitation is that the primary pain endpoint was not assessed. The registry attributes this to early discontinuation because of poor recruitment and states that the study ended before the designated follow-up interval. There are no reported primary outcome observations, responder counts, or comparisons between pregabalin and placebo.
The record does not report how many participants completed each treatment period, whether all enrolled participants were randomized, or which participants were followed for safety. The enrollment entry is 16, while each adverse-event sequence group lists 8 at risk. These entries do not resolve completion or outcome-analysis status.
Important design details are not reported in the registry record, including dose, treatment-period scheduling, washout procedures, allocation procedure, and the roles covered by triple masking. Although the crossover sequences are named, the record does not provide the period-level outcomes needed to evaluate order or carryover effects.
The statistical analysis plan and analysis population are not reported. The registry lists 0 analyses, and does not describe methods for handling missing observations, assessing period effects, or addressing multiple outcomes. As a result, the intended endpoint cannot be linked to a specified statistical model or analysis strategy.
Safety information is limited to the recorded counts for serious and other adverse events in the two sequence groups. Event timing, treatment attribution, and death counts are not reported in the registry record. The counts should therefore be read narrowly rather than as a complete characterization of safety.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Pregabalin for the Treatment of Vulvodynia — NCT00853229.
- Registry record last updated 2021-07-19; status last verified 2021-06.
- Results first posted 2017-05-15.
- 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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18. Record Summary
The registry record describes NCT00853229, titled Pregabalin for the Treatment of Vulvodynia. It lists a Phase 2 randomized, triple-masked, placebo-controlled crossover study sponsored by The Cleveland Clinic, with enrollment of 16. The sequences were pregabalin/placebo and placebo/pregabalin.
The intended primary outcome was reduction in average pain over the last 7 days of each arm on an 11-point scale from 0 to 10, assessed at four weeks. A responder was defined by at least a 50% reduction in pain. A secondary outcome concerned anxiety and depression based on the Kessler Psychological Distress Scale (K10).
The recorded status is TERMINATED. The primary outcome description states that poor recruitment led to early discontinuation before the designated follow-up interval and that no outcomes data were collected. The record lists 0 analyses. Each sequence group reports 0 participants affected by serious adverse events and 0 affected by other adverse events among 8 at risk; deaths are not reported in the registry record.