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 Study to Assess the Effectiveness and Safety of FLECTOR Patch for Treatment of Acute Back Strain (NCT01054820), a na phase 4 study. The primary outcome is Mean Change From Baseline to End of Treatment (EOT) in Response to Modified Brief Pain Inventory (mBPI) Question 5: Average Pain Over the Last 24 Hours.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT01054820 |
| Phase | Phase 4 |
| Condition | Acute Back Strain |
| Allocation | Not applicable (single group) |
| Design model | Single Group |
| Masking | None (open label) |
| Enrollment | 123 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Pfizer |
| Results posted | Yes |
2. Clinical Question
Population
Participants had acute back strain. The primary endpoint population was defined as the intent-to-treat population: participants who had at least one FLECTOR Patch application, pain survey data at baseline, and at least one follow-up visit. The registry record reports enrollment of 123, but does not report how many participants met the primary endpoint population definition or contributed endpoint data.
Intervention
The intervention was FLECTOR Patch, a diclofenac epolamine topical patch at 1.3%. The arm description specifies one patch applied every 12 hours. The study was open-label, so the registry record does not describe masking of participants or investigators to treatment.
Comparator
There was no separate comparator arm. The study is identified as single-group, and allocation is listed as not applicable. A change from baseline can describe the course of measured pain among participants in the group, but without a concurrent control it does not establish how that change compares with another treatment or with no study treatment.
Primary question
The primary question concerned mean change from baseline to end of treatment in participant-rated average pain over the last 24 hours, using Question 5 of the modified Brief Pain Inventory. The scale ranges from 0, no pain, to 10, pain as bad as can be imagined. The endpoint description identifies the measure and assessment times, but the primary endpoint result is not reported in the registry record. Therefore, its direction, magnitude, and precision cannot be assessed from the record.
3. Trial Design
This was a Phase 4, multicenter, open-label, single-group study of FLECTOR Patch for acute back strain. The registry record lists Pfizer as the sponsor, enrollment of 123, a start date of 2010-01, primary completion in 2010-03, and study status as completed. The intervention was a 1.3% diclofenac epolamine topical patch, with one patch applied every 12 hours.
Allocation is listed as not applicable and masking as none. With one treatment group and no randomized comparison, the design describes outcomes during treatment rather than a treatment contrast against a concurrent control group. Changes from baseline can be informative as within-group observations, but they cannot on their own separate treatment effects from other influences on pain over time. General statistical interpretation of uncontrolled change should therefore be cautious.
The registry summary describes the study as an initial step intended to provide information about improvement among participants using the patch and to inform subsequent studies. That stated purpose is consistent with a single-group study, but it does not supply evidence of a controlled comparison. The registry record does not report a protocol rationale for the sample size, a statistical analysis plan, or details about interim analyses. It also does not report the primary endpoint estimates needed to judge the amount of observed change.
The endpoint was assessed at baseline and end of treatment, defined as the last visit up to Day 15. The record describes the primary analysis population as participants with at least one application, baseline pain survey data, and at least one follow-up visit. The number who met those criteria is not reported in the registry record.
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.
Overall Study
| Stage | FLECTOR® Patch (Diclofenac Epolamine Topical Patch) 1.3%. |
|---|---|
| STARTED | 123 |
| COMPLETED | 121 |
| NOT COMPLETED | 2 |
Reasons for not completing this period:
| Reason | FLECTOR® Patch (Diclofenac Epolamine Topical Patch) 1.3%. |
|---|---|
| Withdrawal by Subject | 2 |
Analysis population for the primary outcome, as defined in the registry: Intent to Treat (ITT) population: had at least one application of FLECTOR® Patch, pain survey data at Baseline, and at least 1 follow-up visit. EOT score calculated by taking average of any non-missing scores recorded last 3 days of treatment; if no score on those days, EOT was single, most recent non-missing score recorded on a treatment day.
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 | FLECTOR® Patch (Diclofenac Epolamine Topical Patch) 1.3%. |
|---|---|---|
| Participants analysed | 123 | |
| Age Continuous | years | 38.8 (SD 12.4) |
| Sex: Female, Male: Female | Participants | 60 |
| Sex: Female, Male: Male | Participants | 63 |
6. Primary Endpoint
The registry lists the primary outcome as Mean Change From Baseline to End of Treatment (EOT) in Response to Modified Brief Pain Inventory (mBPI) Question 5: Average Pain Over the Last 24 Hours, measured over Baseline, End of Treatment (last visit up to Day 15).
| Element | Registry entry |
|---|---|
| Result type | Mean |
| Measure of spread | Standard Deviation |
| Unit | scores on a scale |
| Endpoint classification | Continuous Endpoint |
The primary endpoint was mean change from baseline to end of treatment in response to Question 5 of the modified Brief Pain Inventory. Participants rated their average pain over the last 24 hours on an 11-point scale ranging from 0, no pain, to 10, pain as bad as can be imagined. The instrument is participant-rated and also covers functional activities such as general activity, mood, walking ability, relationships, sleep, normal work, and enjoyment of life.
A pain rating is useful because it directly records the participant’s reported experience over a defined recall period. Repeating the measure at baseline and end of treatment allows change over time to be described. As a general statistical explanation, a mean change condenses the observed changes into one average, while the standard deviation describes how spread out the individual values are. The average alone does not show whether individual participants had similar or very different changes.
The registry record specifies baseline and end of treatment as assessment points, with end of treatment defined as the last visit up to Day 15. It describes the end-of-treatment score as an average of nonmissing scores recorded during the last 3 days of treatment, with a fallback based on the most recent score if no score was recorded on those days. The fallback wording ends incompletely in the registry record, so the rule cannot be fully characterized. No primary endpoint mean, mean change, standard deviation, confidence interval, or test result is reported.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record identifies a clinically understandable primary measure: participant-rated average pain over the last 24 hours, assessed at baseline and end of treatment. It also specifies that the endpoint was summarized as mean change and that standard deviation was the dispersion measure. These details explain what was intended to be measured, but they do not provide the numerical endpoint result.
Without the baseline and end-of-treatment values, the mean change, its standard deviation, and the number of participants contributing to the endpoint, the observed pattern cannot be described quantitatively. The registry record does not report whether the average score increased or decreased, how large any change was, or how variable participant-level scores were. It also does not report a confidence interval or inferential test for the primary endpoint. As a result, the precision of the estimate and the compatibility of the data with different possible changes cannot be evaluated from this record.
Direction requires care even when a change estimate is available. The rating scale runs from 0 for no pain to 10 for pain as bad as can be imagined, but the registry record does not state the sign convention used for the change score. A reader would need that convention, along with the actual result, to interpret whether a positive or negative value represents a lower average pain rating.
The single-group design also limits what a change can establish. In general, a before-and-after difference may reflect the passage of time, natural variation in symptoms, expectations in an open-label study, or other influences, as well as any influence of the intervention. Since there is no separate comparator arm, the registry record cannot support a direct estimate of how outcomes differed from a control group. This is a design limitation, not a judgment about the size or importance of any observed change.
The registry lists secondary pain and other measures, including pain ratings at their worst, least, and right now, participant and investigator global pain relief, and a depression inventory measure. Their names indicate the intended outcomes, not their findings. Numerical results for the primary endpoint and these secondary outcomes are not reported in the registry record. Therefore, no overall conclusion about the size, consistency, or statistical uncertainty of changes across outcomes can be drawn from the recorded information.
Safety information is reported separately: the record lists participants affected by serious and other adverse events in the treatment group and identifies a serious-event term. Those counts describe recorded safety outcomes, but they do not fill the gap in the primary effectiveness result. They should be read as descriptive observations in an open-label, single-group study rather than as comparative estimates.
9. Statistical Methods Explained
The registry identifies the primary endpoint as a continuous measure summarized by a mean, with standard deviation as the measure of dispersion. A continuous measure can take values along a scale, rather than being limited to categories such as yes or no. Here, the underlying rating is on a scale from 0 to 10. The primary endpoint is change from baseline to end of treatment, rather than a single rating at one time.
What does mean change represent?
As a general statistical explanation, a participant-level change is formed by comparing a person’s measurement at a later assessment with that person’s baseline measurement. The mean change then describes the average of those participant-level changes in the analysis population. This can summarize the group’s average trajectory, but it does not show the full distribution: some participants can have changes in one direction and others in another. The standard deviation is relevant because it describes spread around the mean; it is not itself a measure of uncertainty in the estimated mean.
The record identifies the endpoint population as participants who had at least one patch application, baseline pain survey data, and at least one follow-up visit. This is the registry’s stated intent-to-treat population definition. The exact number included in that endpoint analysis is not reported. The record also states that the end-of-treatment score uses nonmissing scores from the last 3 days of treatment, with a most-recent-score fallback if there are no scores on those days. The text of that fallback is incomplete, so any additional conditions or handling rules are not reported in the registry record.
How should uncertainty be understood?
As a general explanation, a confidence interval gives a range of values compatible with the data and the assumptions of the method used. Its width reflects statistical precision: a wider interval indicates less precision than a narrower one. A standard deviation and a confidence interval answer different questions. Standard deviation describes variability among measured values; a confidence interval describes uncertainty about an estimated quantity, such as a mean. The registry record does not report a confidence interval for the primary result, so its statistical precision cannot be assessed.
A p-value, when reported, is a measure tied to a specified null hypothesis and statistical model. It is not a measure of the size of an effect, nor does it substitute for an estimate and its uncertainty. No primary endpoint p-value or test method is reported in the registry record. The statistical model, any covariate adjustment, and the method used to calculate uncertainty are also not reported.
Why does the design matter for analysis?
As a general point, a single-group before-and-after analysis estimates change within the group; it does not estimate a randomized treatment contrast. In a controlled trial, an appropriate comparison can help distinguish changes associated with assignment to different groups from changes that might occur over time in either group. This study has no comparator arm, so a within-group change must not be described as a between-group effect. Its open-label status also means participants and investigators were not masked, which can matter when outcomes are self-reported or involve judgment.
The registry record does not report the statistical plan in enough detail to determine whether the primary analysis used a paired test, a model, or another inferential method. It does not specify assumptions about the distribution of changes, how outliers were treated, or whether any sensitivity analyses were performed. These are not details that can be inferred from the endpoint’s mean and standard deviation labels alone.
What do planning calculations mean?
As a general explanation, a sample-size calculation estimates how many participants a hypothetical study might need under stated assumptions about an effect, variability, allocation, and error rates. The registry’s planning assumptions describe an illustration based on the observed effect, with a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation; the stated effect to detect is a fraction of the observed effect. Such an illustration is not a description of this trial’s single-group design, and it is not observed power. Sample sizes used for planning are prospective illustrations, not evidence that a study had a particular probability of detecting an effect after the data were collected. Numerical planning results are not reported in the registry record.
The record does not report the trial’s own sample-size justification or the assumptions used to determine enrollment. It is therefore not possible to assess whether the enrollment target was based on a prespecified clinically meaningful change, a precision objective, feasibility, or another rationale. No new sample-size estimate can be derived without numerical endpoint results and explicit assumptions.
10. Multiplicity, Missing Data and Analysis Populations
The registry record lists 11 outcome measures and 7 analyses. It names several secondary outcomes, including modified Brief Pain Inventory ratings, participant and investigator global pain relief, and a Beck Depression Inventory measure. The existence of multiple outcomes raises a general statistical issue: when many outcomes or analyses are examined, the chance of at least one apparently unusual result can increase if no adjustment or interpretive plan is specified. The registry record does not report a multiplicity strategy, such as a hierarchy of outcomes or an adjustment procedure. It is therefore not possible to determine how multiple analyses were intended to affect interpretation.
Missing-data handling is described only partly for the primary endpoint. The end-of-treatment score was to use any nonmissing scores recorded in the last 3 days of treatment, and, if there were no scores on those days, the description refers to a single most recent score. The record’s wording stops after an incomplete final phrase, so the full fallback rule is not reported. The record does not report the amount or pattern of missing endpoint data, reasons for missing assessments, or sensitivity analyses examining the effect of missingness.
The stated primary analysis population required at least one patch application, baseline survey data, and at least one follow-up visit. The number included in the endpoint analysis is not reported. The record does not say how participants who did not meet these criteria were handled in other analyses, or whether any additional analysis populations were used. It also does not report a general missing-data method such as imputation or a model-based approach.
As a general statistical point, missingness can affect interpretation when the people with recorded follow-up outcomes differ systematically from those without them. Without counts, reasons, and a complete analysis rule, the extent of that concern cannot be evaluated for this study. The registry record likewise does not report whether interim analyses were conducted.
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 |
|---|---|---|---|
| FLECTOR® Patch (Diclofenac Epolamine Topical Patch) 1.3%. | 1 | 123 | 0.8% |
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 |
|---|---|
| FLECTOR® Patch (Diclofenac Epolamine Topical Patch) 1.3%. | 15 of 123 |
Most frequent serious adverse event terms
| Event term | Organ system | FLECTOR® Patch (Diclofenac Epolamine Topical Patch) 1.3%. |
|---|---|---|
| Non-cardiac chest pain | General disorders | 1 of 123 |
Most frequent non-serious adverse event terms
| Event term | Organ system | FLECTOR® Patch (Diclofenac Epolamine Topical Patch) 1.3%. |
|---|---|---|
| Application site rash | Injury, poisoning and procedural complications | 3 of 123 |
| Tachycardia | Cardiac disorders | 2 of 123 |
| Diarrhoea | Gastrointestinal disorders | 1 of 123 |
| Abdominal discomfort | Gastrointestinal disorders | 1 of 123 |
| Abdominal pain | Gastrointestinal disorders | 1 of 123 |
| Nausea | Gastrointestinal disorders | 1 of 123 |
| Folliculitis | Infections and infestations | 1 of 123 |
| Gastroenteritis viral | Infections and infestations | 1 of 123 |
| Upper respiratory tract infection | Infections and infestations | 1 of 123 |
| Application site pruritus | Injury, poisoning and procedural complications | 1 of 123 |
Serious events with the highest arm-level rate: non-cardiac chest pain (0.8%).
The registry record lists one treatment group. It reports 123 participants at risk for serious adverse events and 1 participant affected, and 123 at risk for other adverse events and 15 participants affected. These are descriptive counts for the group; the record does not provide a concurrent control group for comparison. They should not be interpreted as comparative safety estimates.
The listed top serious adverse-event term is non-cardiac chest pain, with 0.8% reported. The record does not provide further detail in the listed information about event timing, severity, relatedness assessment, or the number of events rather than participants for that term. The deaths field is null; deaths are therefore not reported in the registry record, and a null entry should not be converted into a claim that none occurred.
As a general statistical point, the number of participants affected and the number of event occurrences are not necessarily interchangeable: one participant can experience more than one event. The figures should be read according to the labels in the record and not added or treated as a total number of events. Open-label, single-group safety counts describe what was recorded among participants in the study, but cannot by themselves establish how those counts compare with another treatment or with no treatment.
12. What the Result Does, and Does Not, Mean
The record establishes the study’s design, intended primary outcome, analysis population definition, intervention schedule, and some safety counts. It does not report the numerical primary endpoint result. Without that result, readers cannot assess the average change in pain, the variability of the measurements, or the precision of any estimate. The listed secondary outcomes likewise identify what was assessed but do not provide numerical findings.
Even if a within-group change were available, its interpretation would remain bounded by the design. This was a single-group, open-label study without a comparator arm. As a general statistical principle, observed change over time in one group is not equivalent to a treatment effect estimated against a concurrent control. Time, symptom fluctuation, expectations, and other factors may contribute to changes in self-reported outcomes. The registry record does not permit those influences to be separated from one another.
The study’s stated purpose was to provide information about improvement among participants using the patch and to inform subsequent studies. That makes the record relevant as a description of a clinical research question and its measurement approach. It does not supply enough endpoint results to characterize the amount of change or its uncertainty, and it does not establish a controlled comparison. No conclusion about treatment benefit should be drawn from the endpoint description alone.
The safety entries are also limited in scope. They report affected-participant counts and a listed serious adverse-event term, but provide no comparator group or detailed context for interpreting those observations comparatively. The deaths field is not reported. These safety entries and the unreported efficacy endpoint are separate kinds of information; neither should be used to fill gaps in the other.
13. Why This Trial Matters Statistically
Statistically, the study illustrates the difference between defining an outcome and reporting an outcome estimate. The registry record specifies a participant-rated pain scale, its recall period, the assessment window, and a mean-change endpoint. Those details help identify what the investigators intended to measure. But without the numerical change and an uncertainty measure, readers cannot evaluate the size or precision of the result.
The single-group design also makes the distinction between change and comparison especially important. A baseline-to-end-of-treatment description can characterize the measured course among participants, while a controlled comparison addresses how outcomes differ between groups. These are not interchangeable questions. For researchers, the study description underscores why the intended estimand, comparator, population, and analysis method matter when interpreting a trial.
The outcome list further illustrates the need for a prespecified approach to multiple measures. Pain intensity, global relief judgments, and other patient or investigator assessments can address different aspects of a clinical question. When several outcomes are examined, a clear plan helps readers distinguish primary from exploratory findings and understand how multiplicity was handled. Such a plan is not reported in the registry record.
Finally, the record shows why complete reporting matters for reuse and appraisal. The missing primary endpoint estimate, incomplete description of the fallback scoring rule, absent analysis details, and unreported multiplicity strategy limit assessment of the result. The study’s stated role as an initial step for informing subsequent studies makes clear and complete outcome reporting particularly relevant to the design of future research.
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 for statistical interpretation is that the primary endpoint result is not reported in the registry record. The endpoint definition alone cannot establish the average observed change or its precision. Numerical results for the named secondary outcomes are also not included in the record.
The single-group, open-label design has no concurrent comparator. Consequently, within-group changes cannot be interpreted as a randomized contrast, and influences such as time, symptom fluctuation, and expectations cannot be separated by the design. The self-reported primary measure is meaningful as a participant rating, but the open-label setting is relevant context for interpreting such reports.
The endpoint population is defined by treatment exposure and availability of baseline and follow-up data, but its size is not reported. The end-of-treatment scoring description includes an incomplete final phrase, leaving the fallback rule unclear. The registry record also does not report the amount or pattern of missing data, reasons for missing assessments, or sensitivity analyses.
Statistical methods beyond the mean and standard deviation are not reported. The record does not specify the inferential test or model, uncertainty calculation, covariate adjustment, or assumptions used for analysis. A multiplicity strategy is not reported despite several outcomes and analyses being listed. The trial’s own sample-size rationale and interim-analysis details are not reported either. These gaps restrict assessment of both the analysis and the reliability of any endpoint conclusions.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Study to Assess the Effectiveness and Safety of FLECTOR Patch for Treatment of Acute Back Strain — NCT01054820.
- Registry record last updated 2012-08-16; status last verified 2012-07.
- Results first posted 2012-08-16.
- 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 completed Phase 4 study was a multicenter, open-label, single-group evaluation of FLECTOR Patch 1.3% for acute back strain. The registry record reports enrollment of 123 and specifies one patch applied every 12 hours. The primary endpoint was mean change from baseline to end of treatment in participant-rated average pain over the last 24 hours on a scale from 0 to 10.
The endpoint population required at least one application, baseline pain survey data, and at least one follow-up visit. The record describes an end-of-treatment scoring rule but its fallback wording is incomplete. The primary endpoint estimate, its standard deviation, and its inferential results are not reported in the registry record. Safety entries list participants affected by serious and other adverse events and identify non-cardiac chest pain as a top serious-event term. Without a comparator, these counts are descriptive rather than comparative.