Opioid Taper Study: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Opioid Taper Study (NCT03912298), a registered phase not stated study. The primary outcome is Pain Perception Measured Using the Cold-pressor Test (CPT).

2. Clinical Question

3. Trial Design

The registry record identifies NCT03912298, titled “Opioid Taper Study,” with the official title “Effect of Opioid Taper on Pain Responses in Patients With Chronic Pain.” The sponsor is the University of Pennsylvania. The record lists the study as completed, with a start date of 2019-04-15 and a primary completion date of 2021-05-31. Enrollment is listed as 7.

The study description concerns men and women with chronic neuropathic pain receiving high-dose opioid therapy. Participants were to undergo an individualized opioid taper, while experimental pain responses were described serially during and following the taper. The taper length is described as individualized and variable. The registry lists one intervention named “Opioid Taper Pain perception,” classified as “OTHER.”

The record does not describe a randomized comparison, and allocation is not stated. It explicitly does not present the arms as a like-for-like control comparison. Consequently, the design information in the record supports a description of changes observed around tapering, not a controlled estimate contrasting taper with an assigned alternative.

The primary outcome is cold-pressor pain tolerance before and following taper. The outcome description also notes that pain testing order could vary and that evoked pain, temporal summation, and conditioned pain modulation were to be captured at each study session. Although the registry lists two outcome measures, it records no analyses. Details such as the full visit schedule, the exact taper protocol, eligibility criteria, and analysis plan are 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

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.

6. Primary Endpoint

The registry lists the primary outcome as Pain Perception Measured Using the Cold-pressor Test (CPT), measured over up to one year (length of taper individualized and varies).

The primary endpoint is pain perception measured using the cold-pressor test (CPT). Its unit is seconds, and the registry specifies a mean with standard deviation as the summary measure. The reported construct is cold-pressor pain tolerance before and following taper, with a timeframe of up to one year; the length of taper is individualized and varies.

In general, a cold-pressor test is an experimental measure of response to a controlled painful stimulus. Tolerance time is one way to characterize that response. The registry’s description places this measure within a broader assessment of experimental pain, including evoked pain, temporal summation, and conditioned pain modulation. It relates those aspects to hypothesized peripheral, spinal, and supra-spinal mechanisms of opioid-induced hyperalgesia (OIH). This is the rationale stated for measuring them, not a claim that the study established any mechanism.

The endpoint may describe participants’ measured pain tolerance at specified study sessions, but interpretation depends on the actual observations, their timing, and how they were analyzed. Those values and analysis details are not reported in the registry record. The endpoint description therefore explains what was intended to be measured, but cannot establish the direction, size, or precision of any change.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry describes a continuous primary outcome: cold-pressor pain tolerance measured in seconds and summarized using a mean and standard deviation. In general, a continuous outcome can take a range of values rather than only categories. Its mean offers a concise description of the measurement’s central location, while its standard deviation conveys how dispersed the observations are. Neither summary is reported for the primary endpoint in the registry record, so there is no observed estimate to interpret.

What does a mean describe?

In general, a mean combines the observed values into one average. It can be useful when the question concerns a group’s average measured response, as it does in the endpoint description. However, a mean does not show the full shape of the observations. Different patterns of individual measurements can produce the same mean, and unusually high or low values can affect it. The registry does not report the underlying observations or distributional summaries that would allow readers to examine those features.

Why report a standard deviation?

In general, the standard deviation describes the spread of observations around the mean. It is not itself a measure of how precisely the mean has been estimated; precision also depends on how many observations contribute and on the analysis. Because neither the primary mean nor its standard deviation is posted, the record does not permit a numerical assessment of variability in cold-pressor tolerance. The registry lists enrollment, but does not give endpoint-specific counts or the number of observations at each assessment.

How should repeated measurements be considered?

The study description says experimental pain responses were to be serially described over the course of and following an individualized taper. In general, measurements from the same participant over time are related rather than independent. An analysis of repeated observations should account for that dependence if it seeks to estimate a time pattern or an average change. The registry does not report the statistical model, the time points used in an analysis, or any results from such an analysis. It would therefore be inappropriate to infer how repeated data were handled.

The timeframe is listed as up to one year, with taper length individualized and variable. In general, variable assessment timing can complicate comparisons across participants: measurements described as “following taper” may not represent a common elapsed time unless the analysis defines and uses a consistent timing rule. The registry does not report such a rule or the actual measurement schedule. This is a limitation of what can be interpreted from the record, not evidence that a particular analysis was or was not conducted outside the registry.

What would a confidence interval add?

In general, a confidence interval describes uncertainty around an estimated quantity. For a mean change, it can indicate which values are reasonably compatible with the data under the specified analysis. A narrow interval indicates greater precision than a wide interval, though precision is not the same as importance or causality. No confidence interval for the primary outcome is reported in the registry record. There is consequently no posted interval from which to judge the precision of a change estimate.

What can a significance test establish?

In general, a significance test assesses how compatible observed data are with a specified null hypothesis under an analysis model. A p-value does not measure the size of an effect, the probability that a hypothesis is true, or whether a result is clinically important. The registry records no analyses and reports no primary-outcome p-value. No statistical significance claim can therefore be drawn from the posted results.

The record includes sample-size planning assumptions describing 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 also says the effect to detect is a stated fraction of the observed effect. These are described as planning assumptions, not the trial’s own design. No resulting participant-per-arm planning values are reported in the registry record. Such planning illustrations are not observed power and do not establish that the study was designed or analyzed in that way.

Finally, the design is not described as randomized, and allocation is not stated. In general, random assignment can help balance other influences between comparison groups. Without a reported randomized comparator, a before-and-after pattern cannot by itself establish that taper caused a change. The registry record does not report an adjusted analysis or an alternative design feature that would address this limitation.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists two outcome measures and records no analyses. It does not report a statistical analysis plan, the number of hypotheses tested, a hierarchy of outcomes, or any adjustment for multiple comparisons. Thus, the handling of multiplicity is not reported in the registry record. In general, multiplicity arises when several outcomes, time points, or hypotheses are assessed; interpreting isolated statistical tests without knowing the analysis plan can make the evidential strength difficult to judge. No test results are posted from which to assess that issue.

The registry describes multiple aspects of experimental pain response: evoked pain, temporal summation, and conditioned pain modulation. It also mentions functional improvements and subject-level predictors of response. The record does not report which of these were analyzed, how they were defined, or how any analyses were prioritized. These aims cannot be treated as reported findings.

Missing-data details are also not reported in the registry record. There are no endpoint-specific counts by assessment, no description of missing observations, and no account of whether participants stopped contributing measurements. The listed enrollment does not show how many observations were available for each outcome or time point. The record does not state whether missing values were handled through a particular method or whether an analysis used only available observations.

The analysis population is not described. In general, an analysis population defines which participants or measurements contribute to a particular result; it is important because enrollment and outcome-specific availability may differ. Since primary outcome values and analysis populations are not reported, readers cannot assess whether the analyzed data correspond to all enrolled participants or to a subset.

11. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Deaths

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 0% reporting threshold.

The registry’s serious adverse event listing is for the group titled “Chronic Pain Patients Undergoing Opioid Taper.” It records 7 at risk and 0 affected by serious adverse events. The listing also records 7 at risk and 0 affected for other adverse events, and 0 deaths. No serious adverse event terms are listed.

These are registry counts for the recorded group. They should not be read as proof that no adverse events of any kind occurred. The registry distinguishes serious from other adverse events, and the zero count for serious events does not describe symptoms or events that were not classified or reported as serious. The record does not provide event definitions, surveillance procedures, event timing, severity details, or a narrative of individual events.

The adverse event figures also do not provide a comparison with an untreated or alternative-treatment group. The study is not described as a randomized comparison, and allocation is not stated. The counts therefore describe what the registry records for participants undergoing taper, rather than establishing whether risks differed because of taper. The record does not provide further detail on exposure duration or on how adverse-event follow-up related to the individualized taper schedule.

12. What the Result Does, and Does Not, Mean

The registry record documents a completed study of individualized opioid tapering in patients with chronic pain and defines cold-pressor pain tolerance as its primary endpoint. It describes serial experimental pain assessments during and following taper and gives the measurement unit and summary type. Those details clarify the intended outcome, but they are not outcome findings.

The primary outcome values are not reported in the registry record. There is no posted mean, standard deviation, estimate of change, confidence interval, or analysis result. Accordingly, the record does not establish whether pain tolerance increased, decreased, or stayed similar, nor does it show the size or precision of any observed change. Missing outcome results should not be interpreted as a finding of no effect.

The study design information also limits what the described measurements could establish. Allocation is not stated, and the record does not describe a randomized comparison or like-for-like control. A pattern observed before and after an individualized taper would not, by itself, isolate taper as the cause of a change. Other influences over time or differences among participants could also matter, but the record does not provide information to assess them.

The enrollment is listed as 7. The registry does not report how many contributed data at each measurement, whether data were missing, or which analysis population was used. It also does not report results for functional improvement or subject-level predictors, although those topics appear in the study description. No conclusions about those outcomes or associations can be drawn from the record.

In short, the registry establishes the study’s stated purpose, primary measure, design limitations, and recorded adverse-event counts. It does not provide the primary results needed to judge observed change or its uncertainty, and it does not support a causal comparison.

13. Why This Trial Matters Statistically

This study is statistically notable because its stated question involves repeated measurements around an individualized intervention. The description calls for serial assessments during and following taper, rather than a single measurement at a common fixed time. In general, repeated observations can reveal patterns over time, but they also require careful attention to the relationship among measurements from the same participant and to the timing of each measurement.

The taper length is described as individualized and variable, and the primary timeframe is up to one year. That makes the timing of “before” and “following” measurements important to interpretation. A clear account of assessment schedules and the analysis time scale would help readers understand what changes are being compared. Those details are not reported in the registry record.

The study also highlights the distinction between a measured change and a causal effect. The registry does not describe random assignment or a like-for-like control comparison. Even if pre- and post-taper results were available, interpreting them as caused by taper would require caution. The posted record does not report estimates or analyses that could address this question.

Finally, statistical interpretation depends on more than an enrollment figure and a planned outcome definition. Readers need the outcome data, their variability, the number contributing at each assessment, and the analysis methods to evaluate magnitude and precision. The record lists enrollment of 7 and specifies a mean and standard deviation for the primary measure, but does not report the primary results or analysis. The gap between a clearly stated measurement plan and absent results is central to what can be learned from this registry entry.

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.

Several trial-specific limitations of interpretation arise from the registry information. The primary endpoint is defined, but its observed values are not reported. Without the cold-pressor measurements, the stated mean and standard deviation, or an estimate of change, the direction and magnitude of the primary result cannot be evaluated. No confidence interval or inferential result is reported to describe precision.

The registry describes an individualized taper with variable length and a timeframe of up to one year. It does not report the visit schedule, the actual timing of measurements, or how observations were aligned for analysis. This limits interpretation of any before-and-after comparison, even apart from the absence of posted results.

The record does not describe randomized assignment or a control group, and allocation is not stated. It explicitly indicates that the arms are not a like-for-like control comparison. The information therefore does not support a controlled causal contrast. Enrollment is listed as 7, but outcome-specific participation and missingness are not reported, so the available data for each assessment cannot be determined.

Although functional improvements and subject-level predictors are mentioned in the study description, their definitions, results, and analyses are not reported in the registry record. The registry lists two outcome measures but no analyses, and does not report how multiplicity, missing data, or analysis populations were handled. The adverse event listing gives counts, but not event definitions, follow-up details, or a comparison group. These omissions constrain interpretation of both efficacy-related outcomes and safety reporting.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Opioid Taper Study — NCT03912298.
• Registry record last updated 2022-02-07; status last verified 2022-01.
• Results first posted 2022-02-07.
• 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.

18. Record Summary

NCT03912298 is a completed study sponsored by the University of Pennsylvania, with enrollment listed as 7. Its stated purpose is to describe pain sensitivity in patients with chronic pain undergoing an individualized opioid taper. The primary endpoint is cold-pressor pain tolerance in seconds, summarized as a mean and standard deviation, with assessment described before and following taper.

The registry record does not report primary outcome values or analyses. Allocation is not stated, and the study is not described as a randomized, like-for-like control comparison. Serious adverse events are recorded as 0 affected among 7 at risk; other adverse events are also recorded as 0 affected among 7 at risk, with 0 deaths. These registry counts do not replace outcome results or provide a comparative safety estimate.