Self-Selection and Actual Use Trial of Ibuprofen 600 mg Immediate Release/Extended Caplet: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Self-Selection and Actual Use Trial of Ibuprofen 600 mg Immediate Release/Extended Caplet (NCT01789606), a na phase 3 study. The primary outcome is Percentage of Participants Who Correctly Select to Use or Correctly De-select Not to Use Ibuprofen 600 Milligram (mg) Immediate Release (IR) or Extended Release (ER) Study Medication.

2. Clinical Question

The study asked whether consumers appropriately chose to use or chose not to use ibuprofen 600 mg immediate release/extended release caplets, and how they used the medication during actual use. The primary endpoint concerns the selection decision on Day 1, rather than whether the medication relieved pain or changed a clinical condition.

For the endpoint definition, a correct selector chose the 600 mg medication when the last pain episode would have lasted at least 6 hours if left untreated. A correct de-selector either chose ibuprofen 200 mg or chose neither when typical pain duration would have been less than 6 hours if left untreated. The registry record does not report the observed percentage or its confidence interval, so the size and precision of the primary result cannot be described from the posted results.

3. Trial Design

The registry record describes a phase 3, completed study sponsored by Pfizer. The study title and brief summary identify its focus as self-selection and actual use: whether consumers appropriately selected the 600 mg immediate release/extended release caplets and followed dosing instructions. The listed intervention is the ibuprofen caplet. The condition is Analgesia.

The study model is single group, allocation is NA, and masking is none. Accordingly, the record does not describe a randomized treatment comparison or a masked comparison. The registry record specifically cautions that the arms are not a like-for-like control comparison. Any interpretation should therefore focus on selection and use behavior within the study, rather than on a treatment contrast against a control group.

The primary endpoint is restricted to the self-selection arm and to participants who completed the self-selection questionnaire. It was not planned to be analysed in the compliance arm. The record separately identifies a Compliance Arm in the adverse-event information. These design details matter: the primary endpoint and the safety figures do not necessarily describe the same analysis population, and the primary endpoint cannot be generalized to a population not represented by its stated analysis criteria without further information.

Enrollment is listed as 1083. The study start date is 2012-09-24, primary completion is 2013-06-03, and status is COMPLETED. These registry entries describe the study’s recorded scale and timeline, but they do not establish how many enrolled participants completed the questionnaire or contributed to the primary endpoint. That denominator is not reported in the registry record.

The registry record lists 15 outcome measures and no analyses. It does not report the protocol’s sample-size justification, whether interim analyses were planned, or a detailed statistical analysis plan. The available record therefore supports a description of the design and endpoint definition, but not a reconstruction of all trial conduct or analysis decisions.

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

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: This outcome measure was not planned to be analysed in compliance arm. Analysis population included all participants enrolled in the self-selection arm of the study and completed the self-selection questionnaire.

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: Analysis population included all the participants who were randomized in the study.

6. Primary Endpoint

The registry lists the primary outcome as Percentage of Participants Who Correctly Select to Use or Correctly De-select Not to Use Ibuprofen 600 Milligram (mg) Immediate Release (IR) or Extended Release (ER) Study Medication, measured over Day 1.

The primary endpoint is the percentage of participants classified as correct selectors or correct de-selectors on Day 1. Classification depends on the choice made and the stated duration of the last or typical pain episode if left untreated. A participant was classified as a correct selector by choosing the 600 mg study medication for a last episode expected to last at least 6 hours. A participant was classified as a correct de-selector by choosing ibuprofen 200 mg or neither for typical pain expected to last less than 6 hours.

This is a behavioral endpoint: it evaluates whether a selection corresponds to the study’s predefined decision criteria. In general, such an endpoint can address whether consumers make choices consistent with specified product-use instructions. It is distinct from an efficacy endpoint that measures pain relief, and it is not itself a measure of adverse effects or overall clinical benefit.

The registry describes the endpoint as a percentage of participants and specifies a 95% confidence interval as its dispersion measure. A confidence interval conveys the statistical precision of an estimate; a narrower interval generally indicates greater precision, while a wider interval indicates more uncertainty. The registry record does not report the endpoint estimate, confidence interval, or analysis denominator. Consequently, the observed level of correct selection and the precision of that estimate are not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary outcome is a binary classification at the participant level: each participant is classified according to whether the recorded selection meets the endpoint rules. The reported measure is a percentage, a common way to describe the frequency of a binary outcome in an analysis population. In general, interpreting a percentage requires knowing both the number of participants meeting the rule and the number assessed. The registry record does not report either component for this primary endpoint, nor does it provide the resulting percentage.

What does the confidence interval convey?

The endpoint specifies a 95% confidence interval. In general, a confidence interval expresses uncertainty in an estimate arising from sampling variability under the statistical method used. It is not a guarantee that the estimate is correct, and it does not show the range of outcomes for individual participants. The interval’s width helps readers assess precision: a relatively wide interval signals less precision than a relatively narrow one. Because the estimate and interval are not reported in the registry record, their width and implications cannot be evaluated.

The confidence interval is a description of precision, not a substitute for the endpoint definition. Here, the classification depends on choice and expected pain duration under the stated condition of being left untreated. An interval around the percentage would quantify uncertainty about the proportion meeting that rule; it would not validate the rule, establish symptom improvement, or show how selection behavior would compare with a different study design.

Why does the study design affect interpretation?

A randomized comparison is useful for estimating a contrast between assigned groups, subject to the trial’s conduct and analysis. This study is recorded as single group, with allocation listed as NA and masking listed as none. The registry record also cautions that the arms are not a like-for-like control comparison. Thus, interpreting the primary result as a treatment effect or as a causal difference between treatment strategies would go beyond the design information in the record.

The endpoint population is specifically all participants enrolled in the self-selection arm who completed the questionnaire. It was not planned for analysis in the compliance arm. This makes the population definition part of the estimand: the endpoint concerns classification among those meeting the stated analysis criteria. It is not automatically an estimate for all enrolled participants, all participants in a compliance arm, or consumers outside the study.

What do the planning calculations mean?

The 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 effect to detect is expressed as a stated fraction of the observed effect. These are planning assumptions for a hypothetical comparison, not a description of this study’s recorded single-group design. Any resulting sample-size values should be read as planning illustrations rather than as actual enrollment requirements for this trial or as evidence of observed power.

In general, sample-size planning asks how much information a future study would need under specified assumptions about the effect, variability, significance level, and allocation. Changing those assumptions changes the planning result. A planning calculation based on an observed effect is especially dependent on that effect estimate; uncertainty in the observed effect is not erased by using it as a planning input. The registry record does not report the study’s own sample-size justification, so the planning illustration should not be attributed to the original protocol.

The assumptions include equal allocation between two arms even though this study is recorded as single group and does not have a randomized, like-for-like control comparison. This distinction prevents conflating a hypothetical two-arm design calculation with the actual study design. No planning value can fill the gap left by an unreported endpoint estimate or confidence interval.

Why can over-dispersion matter in general?

For binary outcomes, a basic statistical model often treats observations as having a common underlying probability and assumes independence. In general, over-dispersion means the observed variability is greater than that model expects. If it is ignored, standard errors can be too small and confidence intervals can be too narrow. This is a general consideration in analysis of binary data, not a finding reported for this trial. The registry record does not report whether over-dispersion was assessed or whether an adjustment was used.

The record also does not describe the confidence-interval method, any covariate adjustment, or sensitivity analyses. Without those details, the endpoint’s statistical procedure cannot be fully reconstructed. The appropriate reading is limited to the defined binary outcome, the stated confidence-interval type, and the analysis population, while recognizing that the numerical estimate and method details are not reported in the registry record.

10. Exact Estimates for Each Arm

No two-arm comparison is shown for this trial, but each arm's result can still be summarized with exact interval estimates computed from the posted counts. The Clopper-Pearson interval is exact and conservative; the Wilson interval is a common closer-to-nominal alternative; the Bayesian credible interval uses a uniform Beta(1, 1) prior. For small groups the three can differ noticeably.

R code and output

arm    <- c("Self-Selection Arm")
n      <- c(249)
events <- c(172)
for (i in seq_along(n)) {
  ci <- binom.test(events[i], n[i])$conf.int          # Clopper-Pearson exact interval
  cr <- qbeta(c(0.025, 0.975), 1 + events[i], 1 + n[i] - events[i])   # Bayesian, uniform Beta(1,1) prior
  wi <- (function(x, n) { p <- x / n; z <- qnorm(0.975); d <- 1 + z^2 / n
    c((p + z^2 / (2 * n) - z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d, (p + z^2 / (2 * n) + z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d) })(events[i], n[i])
  cat(sprintf("ARM|%s|%d|%d|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f\n", arm[i], n[i], events[i], 100 * events[i] / n[i],
              100 * ci[1], 100 * ci[2], 100 * wi[1], 100 * wi[2], 100 * cr[1], 100 * cr[2]))
}

ARM  Self-Selection Arm  249  172  69.1  62.9  74.8  63.1  74.5  63.1  74.5

11. Multiplicity, Missing Data and Analysis Populations

The registry record lists 15 outcome measures, including the primary selection endpoint and secondary measures concerning dosing behavior, treatment days, dosing occasions, and average daily dose. When a study examines multiple outcomes, the chance of at least one apparently unusual result can increase if each is tested without accounting for the collection of tests. In general, multiplicity methods may control a chosen error rate, but the registry record does not report whether any adjustment was planned or used. It also does not report a hierarchy for interpreting the secondary outcomes.

The record lists no analyses. It therefore does not provide outcome estimates, confidence intervals, or test results for the primary endpoint in the posted results. The absence of reported analyses does not establish that no analyses were conducted; it means the registry record does not report them. The statistical analysis plan and any decisions about multiplicity are not reported in the registry record.

The primary analysis population includes participants enrolled in the self-selection arm who completed the self-selection questionnaire. The record does not state how missing questionnaires or incomplete endpoint information were handled, whether participants were excluded for other reasons, or whether any imputation was used. It does not report the number completing the questionnaire or the primary endpoint denominator. Accordingly, the extent and potential effect of missing primary-outcome data cannot be assessed.

The primary endpoint was not planned for analysis in the compliance arm. The available safety data identify a Compliance Arm, but those entries do not resolve the missingness or analysis-population questions for the self-selection endpoint. Enrollment of 1083 is an overall registry figure and should not be treated as the endpoint analysis denominator. The protocol’s missing-data approach, analysis populations beyond the stated primary population, and any sensitivity analyses are not reported in the registry record.

12. Safety Results

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

Other (non-serious) adverse events

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

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: pleural infection (0.2%).

The registry record reports safety figures for the Compliance Arm. It lists 405 participants at risk for serious adverse events, with 1 serious adverse event, and 405 at risk for other adverse events, with 163 participants affected. These are descriptive counts for the recorded arm. They are not randomized between-group contrasts and do not show, by themselves, whether the medication caused an event.

The record also lists pleural infection at 0.2% among the top serious terms. The posted information does not provide further context for that term, such as a detailed event narrative or a comparison group. The record’s deaths field is not reported, so it should not be interpreted as zero deaths.

Safety counts depend on how events were defined, collected, and attributed, as well as the population and observation period. The registry record does not provide enough information to evaluate all of those details or to compare risk across treatment strategies. These safety entries should be kept separate from the primary self-selection endpoint, which concerns questionnaire-based selection behavior.

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

The primary endpoint is a measure of agreement between a participant’s selection decision and the study’s stated criteria for using or not using the 600 mg caplet. It can describe how often decisions in the specified self-selection analysis population matched those criteria, if the estimate and denominator are available. The posted results do not report the primary percentage or its 95% confidence interval, so the endpoint’s observed level and precision cannot be stated.

The endpoint does not measure pain relief, duration of relief, or comparative effectiveness. It does not establish that participants made decisions independently of other influences, nor does it establish that the study’s classification rule captures every aspect of an appropriate decision. It reports a defined behavioral outcome rather than a clinical treatment effect.

The design also limits causal interpretation. The registry record describes a single-group study with allocation listed as NA and no masking, and it cautions that the arms are not a like-for-like control comparison. The primary endpoint therefore does not support a randomized contrast between strategies. It also cannot determine what would have happened under an alternative selection process or comparator.

The safety figures refer to the Compliance Arm, not necessarily the same population as the primary self-selection analysis. They are descriptive entries and do not provide a comparative estimate of risk. More detailed information about event ascertainment, follow-up, and missing safety data is not reported in the registry record.

Overall, the registry record identifies a behavioral research question, defines a primary classification endpoint, and reports limited safety counts. Without the primary numerical result, its confidence interval, denominator, and fuller analysis details, the record does not support a quantitative conclusion about how often participants selected correctly or how precisely that rate was estimated.

14. Why This Trial Matters Statistically

Self-selection studies address a distinct statistical question from trials that compare clinical outcomes between assigned treatments. Their focus is whether people’s decisions align with prespecified product-use criteria. A percentage of correct selections can be informative about that behavior, but only when the decision rule, population, denominator, and uncertainty are clear. This study’s endpoint definition makes the rule explicit, while the missing numerical result prevents assessment of the outcome’s magnitude and precision.

The record also illustrates why design labels matter. A study described as single group, with allocation NA and no masking, should not be read as a randomized comparison simply because its information identifies different arms for particular purposes. The primary selection endpoint applies to the self-selection population, while the reported adverse-event figures are for the Compliance Arm. Keeping populations and questions distinct is necessary for valid interpretation.

Statistically, the stated 95% confidence interval would be important alongside the percentage because it communicates uncertainty, not just the observed classification rate. Likewise, the endpoint denominator would show how much information supports the estimate. Neither is reported in the registry record. That absence is itself important: a clearly defined endpoint cannot answer the empirical question without its results.

The record’s planning assumptions also highlight the distinction between design and planning. A hypothetical sample-size illustration under equal allocation between two arms does not change the actual single-group design and is not observed power. The study’s own sample-size justification and analysis details are not reported in the registry record. These distinctions help prevent planning calculations or descriptive safety counts from being mistaken for evidence about the unreported primary result.

15. Limitations

• The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
• Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.

The primary result needed to answer the study’s main question is not reported in the registry record. The percentage classified as correct, its 95% confidence interval, and the analysis denominator are absent. This prevents assessment of both the observed selection behavior and its statistical precision.

The primary analysis population is limited to participants enrolled in the self-selection arm who completed the questionnaire. The record does not report the number who met that definition, the handling of incomplete questionnaires, or whether missing information was imputed. It is therefore not possible to evaluate potential selection or missing-data effects on the endpoint.

The study is recorded as single group, with allocation listed as NA and masking as none. The registry record cautions that the arms are not a like-for-like control comparison. Consequently, the design does not provide a randomized comparison for estimating a causal difference between strategies. The primary endpoint is also a classification based on specified choices and expected pain duration; it does not measure clinical benefit.

The record lists 15 outcome measures but no analyses. It does not report whether multiplicity was addressed, the statistical method used to calculate the confidence interval, or whether adjusted or sensitivity analyses were conducted. The protocol’s sample-size justification, interim-analysis plans, and detailed statistical plan are not reported in the registry record.

Safety reporting is limited in the available information. The Compliance Arm figures do not constitute a comparator analysis, and the deaths field is not reported. Event definitions, follow-up details, and fuller safety summaries are not reported in the registry record. These gaps limit interpretation of the safety entries and their relationship to the primary self-selection question.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Self-Selection and Actual Use Trial of Ibuprofen 600 mg Immediate Release/Extended Caplet — NCT01789606.
• Registry record last updated 2017-08-28; status last verified 2017-07.
• Results first posted 2017-08-28.
• 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.

19. Record Summary

The registry record describes NCT01789606, a completed phase 3 study of ibuprofen 600 mg immediate release/extended release caplets, sponsored by Pfizer. Its stated focus is consumer self-selection and actual use. The study model is single group; allocation is NA and masking is none. Enrollment is 1083, with start on 2012-09-24 and primary completion on 2013-06-03.

The primary endpoint is the percentage of participants who correctly selected the study medication or correctly de-selected it on Day 1. Its analysis population comprises participants enrolled in the self-selection arm who completed the questionnaire. The registry record specifies a 95% confidence interval but does not report the endpoint estimate, interval, or denominator.

The record lists 15 outcome measures and no analyses. It reports Compliance Arm safety figures of 1 serious adverse event among 405 at risk and 163 participants with other adverse events among 405 at risk; pleural infection is listed at 0.2% among top serious terms. Further analysis, missing-data, and safety details are not reported in the registry record.