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 Measuring Gait And Self-Reported Pain In Patients With Osteoarthritis Of The Knee Using Placebo/Oxycodone/Celecoxib. (NCT00484718), a randomized phase 4 study. The primary outcome is Change From Baseline in Knee Pain Intensity Measured by Numeric Rating Scale (NRS) at Week 12.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT00484718 |
| Phase | Phase 4 |
| Condition | Osteoarthritis |
| Allocation | Randomized |
| Design model | Crossover |
| Masking | Double |
| Enrollment | 6 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Pfizer |
| Results posted | Yes |
2. Clinical Question
Population
Participants with osteoarthritis of the knee. The registry reports 6 enrolled. It does not give further eligibility details in the record.
Intervention
The active treatments were celecoxib and oxycodone. The registry lists celecoxib and Oxycodone as drug interventions, and the adverse-event groups specify Celecoxib 100 mg and Oxycodone 20 mg.
Comparator
Placebo was the comparison treatment. The study title describes a crossover pilot using placebo, oxycodone and celecoxib, but the record does not provide treatment sequences or a detailed account of the periods.
Primary question
The planned primary endpoint was change from baseline in knee pain intensity, measured by an 11-point Numeric Rating Scale at Week 12. The registry says this outcome was not collected or analyzed after termination because too few participants enrolled to carry out the prespecified efficacy analysis.
The central question was whether this crossover design could be used to evaluate osteoarthritis endpoints and characterize variability within and between participants. The study also sought to assess whether efficacy could be detected by measuring those endpoints after treatment with two types of analgesics. These were stated aims, not findings: the planned primary pain data were not available for analysis. The record therefore does not establish whether pain changed with any of the treatments or whether the design could detect a treatment effect.
3. Trial Design
This was a Phase 4, randomized crossover pilot trial in participants with osteoarthritis of the knee. The registry lists the masking as double and the model as crossover. Its official title describes a single-blind washout followed by double-blind treatment, with a double-dummy design. These descriptions give the broad design features, but the registry record does not report the treatment sequence, the duration or conduct of washout, or the specific procedures used to preserve masking.
The interventions were placebo, celecoxib and oxycodone. The adverse-event groups identify the active treatments as Celecoxib 100 mg and Oxycodone 20 mg. The brief summary says the study was intended to evaluate use of a crossover design in an osteoarthritis population, including inter- and intra-subject variability in osteoarthritis endpoints. In general, a crossover design measures participants under more than one treatment condition, allowing comparisons that account for participant-level characteristics. That general feature does not establish how this particular trial assigned or ordered its treatments.
The registry reports 6 participants enrolled. The study started on 2008-01-17, had a primary completion date of 2009-06-10, and is listed as terminated. The reason given for the absence of the primary outcome is the low number enrolled, which meant the prespecified efficacy analysis could not be carried out. The record does not report detailed recruitment progress, the protocol’s intended enrollment, or a fuller explanation of the termination decision.
The trial’s planned primary outcome was change from baseline in signal-knee pain intensity at Week 12. Although the registry lists 14 outcome measures, it reports no analyses for them. The arm descriptions are blank, and the record does not provide a detailed account of treatment-period timing or the allocation procedures beyond stating that allocation was randomized.
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: Total 6 participants were randomized to receive 1 of 6 possible treatment sequences of ABC, ACB. BAC, BCA, CAB, CBA (where: A=placebo, B=celecoxib, C=oxycodone) in treatment periods 1, 2 and 3 (each 2-week treatment period was separated by a 2-week washout period).
Treatment Period 1 (2 Weeks)
| Stage | Placebo Then Celecoxib Then Oxycodone | Placebo Then Oxycodone Then Celecoxib | Celecoxib Then Placebo Then Oxycodone | Celecoxib Then Oxycodone Then Placebo | Oxycodone Then Placebo Then Celecoxib | Oxycodone Then Celecoxib Then Placebo |
|---|---|---|---|---|---|---|
| STARTED | 1 | 1 | 1 | 1 | 1 | 1 |
| COMPLETED | 1 | 1 | 1 | 1 | 1 | 1 |
| NOT COMPLETED | 0 | 0 | 0 | 0 | 0 | 0 |
Washout Period (2 Weeks)
| Stage | Placebo Then Celecoxib Then Oxycodone | Placebo Then Oxycodone Then Celecoxib | Celecoxib Then Placebo Then Oxycodone | Celecoxib Then Oxycodone Then Placebo | Oxycodone Then Placebo Then Celecoxib | Oxycodone Then Celecoxib Then Placebo |
|---|---|---|---|---|---|---|
| STARTED | 1 | 1 | 1 | 1 | 1 | 1 |
| COMPLETED | 1 | 1 | 1 | 1 | 1 | 1 |
| NOT COMPLETED | 0 | 0 | 0 | 0 | 0 | 0 |
Treatment Period 2 (2 Weeks)
| Stage | Placebo Then Celecoxib Then Oxycodone | Placebo Then Oxycodone Then Celecoxib | Celecoxib Then Placebo Then Oxycodone | Celecoxib Then Oxycodone Then Placebo | Oxycodone Then Placebo Then Celecoxib | Oxycodone Then Celecoxib Then Placebo |
|---|---|---|---|---|---|---|
| STARTED | 1 | 1 | 1 | 1 | 1 | 1 |
| COMPLETED | 1 | 1 | 1 | 1 | 1 | 1 |
| NOT COMPLETED | 0 | 0 | 0 | 0 | 0 | 0 |
Washout Period (2 Weeks)
| Stage | Placebo Then Celecoxib Then Oxycodone | Placebo Then Oxycodone Then Celecoxib | Celecoxib Then Placebo Then Oxycodone | Celecoxib Then Oxycodone Then Placebo | Oxycodone Then Placebo Then Celecoxib | Oxycodone Then Celecoxib Then Placebo |
|---|---|---|---|---|---|---|
| STARTED | 1 | 1 | 1 | 1 | 1 | 1 |
| COMPLETED | 1 | 1 | 1 | 1 | 1 | 1 |
| NOT COMPLETED | 0 | 0 | 0 | 0 | 0 | 0 |
Analysis population for the primary outcome, as defined in the registry: As study was terminated, data for this outcome measure was not collected and analyzed due to low number of participant enrolled which were required to carry out the pre-specified efficacy analysis.
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: Baseline analysis population included all randomized participants who received at least 1 dose of study medication.
| Characteristic | Unit | All Participants |
|---|---|---|
| Participants analysed | 6 | |
| Age, Continuous | Years | 62.5 (SD 4.8) |
| Sex: Female, Male: Female | Participants | 2 |
| Sex: Female, Male: Male | Participants | 4 |
6. Primary Endpoint
The registry lists the primary outcome as Change From Baseline in Knee Pain Intensity Measured by Numeric Rating Scale (NRS) at Week 12, measured over Baseline, Week 12.
| Element | Registry entry |
|---|---|
| Result type | N/A |
| Measure of spread | not applicable |
| Unit | not stated |
| Endpoint classification | not reduced to a single comparison |
The planned primary endpoint was change from baseline in knee pain intensity measured by a Numeric Rating Scale at Week 12. Participants were asked to rate the severity of arthritis pain in their signal knee at the time of the visit. The scale ranged from 0 (no pain) to 10 (worst possible pain), with higher scores indicating worse pain.
A pain rating is a patient-reported measure: it records the participant’s experience rather than a laboratory or imaging measurement. Change from baseline is generally used to describe how a measure differs from its starting value during follow-up. In this trial, the registry specifies baseline and Week 12 as the relevant time points, but it gives no endpoint values, summary statistics, or treatment comparisons.
The registry states that the study was terminated and that data for this outcome were not collected and analyzed because the number enrolled was too low for the prespecified efficacy analysis. Accordingly, the endpoint describes the question the trial intended to address, not an observed result. There is no posted estimate of average pain change, no measure of variability for this outcome, and no confidence interval with which to assess the precision of a treatment comparison.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The main interpretive point is that the posted record does not contain an efficacy result for the primary endpoint. It identifies a planned measure, change from baseline in signal-knee pain at Week 12, and explicitly states that the data were not collected and analyzed. The trial’s termination after 6 participants enrolled prevented the prespecified efficacy analysis. No treatment effect estimate or uncertainty interval for pain is reported.
That absence is different from a result showing no change or no difference. A lack of analyzed primary outcome data cannot establish that placebo, celecoxib and oxycodone produced the same pain outcomes, nor can it establish that one treatment produced a larger change. The record does not give estimates that could support either conclusion. It also does not report the planned efficacy analysis methods in enough detail to reconstruct them.
The brief summary frames the study as a test of whether a crossover design could be used to evaluate osteoarthritis endpoints, including variability within and between participants. The enrollment and missing endpoint data show that the intended efficacy assessment was not completed as described in the record. They do not, by themselves, quantify the reliability of any endpoint or demonstrate what a fully completed crossover analysis would have found.
The record lists 14 outcome measures, but reports 0 analyses. This means the page should be read as a record of a terminated study with an unreported primary efficacy result, not as a comparative efficacy report. The listed adverse-event counts are available, but they are descriptive counts and do not replace the missing pain outcome. They also should not be treated as evidence of comparative safety from a small crossover study.
Confidence intervals are generally used to show the range of estimates compatible with the data under an analysis model. Here, no primary endpoint estimate or confidence interval is posted, so precision cannot be assessed for the planned pain comparison. The small enrollment is relevant context for why the prespecified efficacy analysis was not performed, but it does not justify inventing a result or interpreting the missing analysis as a null finding.
9. Statistical Methods Explained
The record identifies randomization, double masking and a crossover model. It does not report a statistical analysis plan in enough detail to explain the intended model, treatment contrasts, handling of period or sequence effects, or assumptions about within-participant correlation. The trial title adds that it used a washout and double-dummy approach, but the registry record does not provide operational details for those procedures. The sections below explain the statistical ideas relevant to the listed design in general; they do not claim that each method was used in this trial.
What does a crossover design contribute?
In general, a crossover design observes participants under different treatment conditions, rather than assigning each participant to remain in only one treatment condition throughout the study. Because a participant can serve as a reference for their own measurements, comparisons can account for some stable differences between participants. This can be useful when the research question includes within-participant variability, as this study’s brief summary states.
The design also requires attention to how treatment periods are arranged and analyzed. Measurements may vary over time, and the treatment received in an earlier period could matter for a later measurement if its effects carry over. Washout periods are intended to address that general concern, but the registry does not report the schedule or analysis used to evaluate carryover, period effects, or sequence effects. It would therefore be inappropriate to assume these effects were absent or that a particular adjustment was made.
What was the primary outcome intended to summarize?
The primary outcome was change from baseline in signal-knee pain intensity at Week 12, using the NRS described in the endpoint section. In general, a change score summarizes how a participant’s measurement differs from a reference measurement. A treatment comparison would require the observed values and a defined statistical analysis. The registry reports neither for this endpoint: it states that the outcome was not collected and analyzed because enrollment was too low for the prespecified efficacy analysis.
The registry’s general sample-size assumptions describe an illustration based on an observed effect, with a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. It says the effect to detect is a stated fraction of the observed effect. Those assumptions describe planning illustrations, not the trial’s observed efficacy results or its own design justification. The record does not report a sample-size justification for this trial, and no observed primary effect is available to interpret as evidence of efficacy. Any sample-size illustration on the page should be read as planning context, not observed power.
How should uncertainty and significance be understood?
In general, a treatment estimate describes the direction and size of an observed difference under a specified analysis. A confidence interval describes statistical uncertainty around that estimate: a wider interval indicates less precision, while a narrower interval indicates greater precision, subject to the model and data. A significance test addresses compatibility with a specified null hypothesis under its assumptions. These tools answer different questions and do not replace consideration of study design, missing data, or the size and relevance of an effect.
For this trial’s primary outcome, there is no posted estimate, confidence interval, or significance test to interpret. The registry reports 0 analyses. No p-value for the planned pain outcome is available. It is therefore not possible to evaluate statistical significance or the precision of a treatment effect from the record.
Why does a small crossover study still need appropriate analysis?
In general, crossover observations from the same participant are related rather than independent. An analysis that ignores this relationship may misrepresent uncertainty. Crossover analyses may also need to account for treatment period and sequence, depending on the protocol and data. When the number enrolled is small, estimates can be especially uncertain, and the observed sample may not support a complex analysis reliably. These are general considerations, not a description of methods used: the registry does not report an analysis model or estimates for the primary outcome.
Over-dispersion is a general issue when the variability in data is greater than a model expects. If present, it can make standard errors and significance tests based on the simpler model unreliable. Whether over-dispersion was assessed in this trial is not reported in the registry record, and the endpoint’s unavailability means it cannot be evaluated from posted primary outcome results.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists 14 outcome measures but reports 0 analyses. It identifies a primary endpoint, yet the record says that this outcome was not collected and analyzed after termination. Consequently, there are no posted estimates with which to assess how the primary endpoint was treated relative to other outcomes.
Multiplicity refers, in general, to the added chance of finding a seemingly notable result when many outcomes, time points, or comparisons are examined. Study plans can address this by defining a primary question and specifying how additional comparisons will be interpreted or adjusted. The registry record does not report a multiplicity procedure, a hierarchy for the other outcome measures, or which comparisons were intended beyond the primary endpoint description. It would be speculative to say that any particular adjustment was planned or applied.
The record gives a reason for missing primary outcome data: the study was terminated, and the number enrolled was too low to carry out the prespecified efficacy analysis. It says the data were not collected and analyzed. It does not report the amount or pattern of missingness for other outcomes, any imputation method, or sensitivity analyses. General missing-data methods can address incomplete observations under stated assumptions, but no such method is reported.
The record also does not describe analysis populations, such as which participants would have been included in the planned efficacy analysis, or how adherence and incomplete treatment periods would have been handled. These details are not reported in the registry record. In their absence, the enrollment count should not be confused with a completed analysis population, and there is no basis for reconstructing a treatment comparison.
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 |
|---|---|---|---|
| Placebo | 0 | 6 | 0.0% |
| Celecoxib 100 mg | 0 | 6 | 0.0% |
| Oxycodone 20 mg | 0 | 6 | 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 |
|---|---|
| Placebo | 5 of 6 |
| Celecoxib 100 mg | 4 of 6 |
| Oxycodone 20 mg | 6 of 6 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Placebo | Celecoxib 100 mg | Oxycodone 20 mg |
|---|---|---|---|---|
| Nausea | Gastrointestinal disorders | 1 of 6 | 2 of 6 | 3 of 6 |
| Somnolence | Nervous system disorders | 1 of 6 | 0 of 6 | 3 of 6 |
| Constipation | Gastrointestinal disorders | 0 of 6 | 0 of 6 | 3 of 6 |
| Diarrhoea | Gastrointestinal disorders | 1 of 6 | 0 of 6 | 2 of 6 |
| Dizziness | Nervous system disorders | 1 of 6 | 1 of 6 | 1 of 6 |
| Headache | Nervous system disorders | 0 of 6 | 1 of 6 | 2 of 6 |
| Dyspepsia | Gastrointestinal disorders | 0 of 6 | 1 of 6 | 1 of 6 |
| Flatulence | Gastrointestinal disorders | 0 of 6 | 1 of 6 | 1 of 6 |
| Vision blurred | Eye disorders | 1 of 6 | 0 of 6 | 0 of 6 |
| Chills | General disorders | 0 of 6 | 0 of 6 | 1 of 6 |
The registry reports serious adverse events for each listed treatment group as 0 affected among 6 at risk: Placebo, Celecoxib 100 mg and Oxycodone 20 mg. The deaths field is null for each group, so a death count is not reported in the registry record; null should not be read as a reported count of zero.
For other adverse events, the record reports 5 affected among 6 at risk for Placebo, 4 among 6 for Celecoxib 100 mg, and 6 among 6 for Oxycodone 20 mg. These are the posted counts for participants affected, not counts of event episodes or measures of severity. The record does not provide the event terms in the registry record, so the counts cannot describe which events occurred.
In general, adverse-event counts describe what was recorded in the observed study population; they do not by themselves establish that a treatment caused an event. This was a crossover trial, and the same participants may contribute observations under different treatment conditions. The treatment-group counts should therefore not automatically be interpreted as independent groups of participants. With 6 enrolled and no primary efficacy analysis, these safety figures are descriptive and do not provide a precise comparative safety assessment.
12. What the Result Does, and Does Not, Mean
This trial record documents an attempt to evaluate a crossover design for measuring osteoarthritis endpoints, with placebo, celecoxib and oxycodone as the listed interventions. It also identifies a planned patient-reported pain endpoint at Week 12. Those details show what the study set out to examine, but they are not evidence that any treatment changed pain.
The registry reports that the study was terminated after 6 participants enrolled, and that the primary pain outcome was not collected and analyzed because the number enrolled was too low for the prespecified efficacy analysis. As a result, the posted record does not provide a treatment effect estimate, uncertainty interval or significance test for the primary question. The absence of these results cannot be interpreted as evidence of no effect, equal effects, or a treatment benefit.
The record does provide adverse-event counts, including serious adverse events and other adverse events by treatment label. These counts are descriptive and do not substitute for the missing efficacy analysis. They should be interpreted cautiously because the study was small and used a crossover design; the group labels do not necessarily represent separate sets of participants.
The trial also cannot establish from the available record whether the planned crossover approach would have adequately measured within- and between-participant variability. The brief summary states that assessing those features was an objective, but no relevant estimates or completed analyses are posted. The record is therefore informative about the study’s intended question and why its primary analysis was not completed, rather than about comparative treatment effects.
In general, statistical conclusions depend on the observed data, the design, the analysis and the uncertainty around estimates. Here, the primary outcome data needed for those conclusions are explicitly absent. The most defensible reading is limited: the trial was terminated after low enrollment, and its planned efficacy question remains unanswered in the registry record.
13. Why This Trial Matters Statistically
The trial is statistically notable because its stated aim was not limited to comparing treatments. The brief summary says it sought to evaluate a crossover design in an osteoarthritis population, characterize inter- and intra-subject variability in osteoarthritis endpoints, and assess whether efficacy could be detected using those endpoints after treatment with two types of analgesics. These aims make measurement and design feasibility central to the question.
A crossover design can be attractive in general when within-participant comparisons are useful, because each participant may provide measurements under different treatment conditions. But the design depends on collecting and analyzing the planned measurements across periods. Treatment order, period effects, carryover, and within-participant correlation may matter. The registry does not report enough protocol or analysis detail to assess how those issues were handled, and the primary data needed for an efficacy analysis were not collected and analyzed.
The termination after 6 participants enrolled highlights a distinction between a design’s statistical rationale and the evidence actually available. A design may be intended to improve comparisons or characterize variability, yet it still requires sufficient observed data to estimate those quantities. Here, no primary outcome estimate or analysis is posted, so the record cannot tell readers how precise a crossover comparison would have been or whether the targeted endpoints were informative.
The study is also a useful example of why a planned endpoint must not be mistaken for a result. The registry names a specific patient-reported pain measure and time point, but explicitly records that the measure was not collected and analyzed. That is not a negative treatment finding. It is an uncompleted efficacy assessment, with the original design question unresolved in the posted record.
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 primary limitation is the absence of the planned efficacy data. The registry states that the Week 12 pain endpoint was not collected and analyzed because enrollment was too low for the prespecified efficacy analysis. There is consequently no primary effect estimate, confidence interval or test result to interpret.
Enrollment was 6, and the study is listed as terminated. The record does not give the planned enrollment target, a sample-size justification for the trial, or further detail about recruitment and the termination decision. It also does not report the full protocol or statistical analysis plan. In particular, treatment sequence, washout procedures, period-specific timing, carryover assessment, and the model for the crossover data are not reported in the registry record.
Although the record lists 14 outcome measures, it reports 0 analyses. It does not describe the intended analysis populations, how incomplete observations would be handled, or any missing-data or multiplicity procedures. The arm descriptions are blank, and the primary endpoint fields for unit, parameter and dispersion are null. These omissions limit interpretation beyond the explicit description of the NRS and the reason the primary outcome was unavailable.
The safety information is also limited. Serious adverse events are reported as 0 affected among 6 at risk in each listed treatment group, while deaths are null rather than given as counts. Other adverse-event counts are posted, but the registry record does not provide the event terms. Because the study used a crossover design, treatment-group counts should not be assumed to represent independent participant groups. These limitations mean the safety counts are descriptive and do not support a precise comparative conclusion.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Measuring Gait And Self-Reported Pain In Patients With Osteoarthritis Of The Knee Using Placebo/Oxycodone/Celecoxib. — NCT00484718.
- Registry record last updated 2021-04-14; status last verified 2021-03.
- Results first posted 2021-04-14.
- 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.
Continue through the Clinical Biostats statistical pathway
Use this trial's endpoint as a starting point for deeper study of effect measures, confidence intervals, and sample-size planning.
18. Record Summary
This Phase 4 randomized crossover pilot trial studied placebo, celecoxib and oxycodone in participants with knee osteoarthritis. The registry lists double masking and describes a crossover model; the official title specifies a washout and double-blind treatment with a double-dummy design.
The planned primary endpoint was change from baseline in signal-knee pain measured with an 11-point NRS at Week 12. The study was terminated after 6 participants enrolled, and the registry states that this outcome was not collected and analyzed because enrollment was too low for the prespecified efficacy analysis. The record lists 14 outcome measures and 0 analyses.
Posted safety counts include 0 serious adverse events among 6 at risk in each treatment group. Other adverse events affected 5 among 6 in the placebo group, 4 among 6 in the celecoxib group and 6 among 6 in the oxycodone group. The registry does not report a primary efficacy result, so the treatment question remains unanswered by the posted data.