Split Dose Golytely With Amitiza Pretreatment Versus Split Dose Golytely Plus Placebo in Outpatient Colonoscopy: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Split Dose Golytely With Amitiza Pretreatment Versus Split Dose Golytely Plus Placebo in Outpatient Colonoscopy (NCT00611442), a randomized na study. The primary outcome is The Overall Cleanliness of the Prep as Measured by the Ottawa Scale.

2. Clinical Question

The comparison is about the quality of bowel cleansing observed at colonoscopy, rather than a direct measure of a participant’s health after the procedure. The scale description indicates that lower scores represent better preparation: excellent preparation is associated with scores from 0 to 3, good preparation with scores from 4 to 6, and higher scores indicate progressively worse preparation. Its total range is 0 to 14.

The registry also lists patient satisfaction, procedure time, and the number of polyps detected as secondary outcomes. These address different aspects of the preparation and procedure, but they do not replace the primary cleanliness question. The record does not report a primary between-arm statistical analysis, so the posted arm summaries alone do not establish how precisely the groups differed or whether the observed separation is compatible with chance variation.

3. Trial Design

This was a randomized, double-blind, parallel-group trial listed as completed. The registry describes the study as a comparison of split-dose PEG bowel preparation with lubiprostone pretreatment versus the same preparation with placebo pretreatment. The official title specifies that the PEG solution was used without dietary restrictions. The study concerned bowel preparation before outpatient colonoscopy.

The registry reports enrollment of 191. For the primary outcome, the posted results list 94 participants in the Amitiza arm and 94 in the placebo arm. The record does not explain the difference between the enrollment figure and the numbers shown for the primary outcome, and it does not report the analysis population or how missing outcome data were handled. It is therefore not possible to determine from the registry alone whether the outcome summaries include all randomized participants or a defined subset.

The Ottawa score was assessed by each endoscopist during endoscopy. The registry says that neither the endoscopist nor the endoscopy nurse was aware of the bowel preparation used before colonoscopy. This describes blinding for those procedure staff; the record does not provide a fuller account of who else was masked or how masking was maintained.

The study’s primary completion period is recorded as 2008-01, with an approximately 4 month period referenced for outcome collection. The sample-size justification, planned statistical analysis, allocation method details, and any interim analyses are not reported in the registry record. The posted results include primary outcome arm summaries and secondary outcome summaries, but no reported analyses are listed.

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 The Overall Cleanliness of the Prep as Measured by the Ottawa Scale, measured over measured upon completion of the colonoscopy, colonoscopies completed during the course of the study (approximately 4 month period).

The primary endpoint is overall cleanliness of the bowel preparation, measured using the Ottawa bowel preparation scale during colonoscopy. The registry describes assessment of the right, mid, and rectosigmoid sections, each rated on a 5-point scale from 0 to 4, together with a global rating of colonic fluid on a 3-point scale from 0 to 2. These components contribute to a total score from 0 to 14.

The scale is used to summarize the endoscopist’s assessment of bowel cleansing across colon regions and fluid. The registry describes lower scores as better: scores from 0 to 3 indicate excellent preparation, scores from 4 to 6 indicate good preparation, and scores higher than 7 indicate progressively worse preparation. A completely unprepared colon is described as scoring from 11 to 14, depending on the amount of fluid.

Assessing preparation during colonoscopy ties the endpoint to the condition of the colon at the time of the procedure. The record calls the scale validated and says it was used to provide a reliable quality assessment. However, it does not report a primary between-group estimate or uncertainty interval. The arm means and full ranges shown in the results describe the observed scores, but they do not by themselves quantify the precision of a group comparison.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary outcome is reported as a mean with a full range for each arm. A mean summarizes the scores by their average, while the full range gives the lowest and highest recorded scores. These summaries answer different questions. The mean describes the center of the observations in a compact way; the range indicates their observed extremes. A range does not show whether most scores clustered near the mean or were spread broadly across the scale.

The Ottawa score combines ratings across colon regions and fluid. The registry describes a bounded score from 0 to 14, with lower values representing better preparation. Because it combines ratings, the mean can be useful for summarizing the average level of cleanliness, but it can hide variation in the pattern of component ratings. The record does not post component-level outcomes, so readers cannot see whether any particular colon section or fluid rating contributed more to the arm summaries.

A treatment comparison ordinarily needs more than two arm means. A difference estimate would summarize the direction and size of the contrast, and a confidence interval would communicate the uncertainty around that estimate. In general, a confidence interval is a range of values compatible with the data under the method used; narrower intervals indicate greater precision, while wider intervals indicate less precision. The registry does not report such an estimate or interval for the primary outcome. The result display therefore should be read as descriptive, not as a complete analysis of the primary comparison.

The registry identifies the primary outcome summary as a mean and full range, but it does not state a primary test or model. It does not report an adjustment strategy, covariates, or a planned method for handling the bounded score. Those choices are not recoverable from the reported arm summaries and are not reported in the registry record. It would be inappropriate to infer them from the appearance of the results.

What the secondary estimates represent

For patient satisfaction and procedure time, the page includes simple unadjusted re-calculations from the posted arm-level means, standard deviations, and sample sizes. In general, an unadjusted comparison uses the reported group summaries without controlling for other variables. Its estimate describes the contrast suggested by those summaries under the stated calculation, rather than an adjusted sponsor analysis. No sponsor-reported analyses are listed in the registry.

The secondary results show confidence intervals and unadjusted p-values. In general, a p-value measures how compatible the observed data are with a specified null hypothesis under a statistical model; it is not the probability that the null hypothesis is true, nor a measure of clinical importance. A confidence interval adds information about the range of effect sizes compatible with the data under the method. These concepts are useful only with their assumptions in view, and the registry does not provide a full analysis plan for these outcomes.

Standard deviations describe the spread of individual measurements around a mean. Over-dispersion is a general concern when the variability in data is greater than a model assumes; if a model understates variability, its uncertainty estimates can be too small. That issue is relevant in general when selecting models for clinical outcomes, but the record does not report a model-based analysis of the primary score or enough information to assess whether over-dispersion was considered.

How to read the planning illustrations

The sample-size display is a planning illustration based on observed secondary effects, not the design calculation for this trial. Its stated assumptions are a two-sided significance level of 0.05, equal allocation, a normal approximation, and effects expressed as fractions of the observed effect. The listed participant counts are planning illustrations for future studies; they are not observed power and do not show that this trial was designed to achieve a particular power. The trial’s own sample-size justification is not reported in the registry record.

In general, power describes the probability that a planned analysis will detect a specified effect under its assumptions. A calculation based on an effect observed in the same study can be useful for illustrating future planning, but it should not be read as a retrospective measure of how informative the completed trial was. A trial’s precision is more directly conveyed by its estimated effects and uncertainty intervals. For the primary endpoint, those comparative quantities are not reported.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists one primary outcome and several secondary outcomes, but it does not report a statistical analysis plan describing how comparisons across outcomes were to be handled. A multiplicity adjustment or a prespecified testing sequence is not reported in the registry record. In general, when several hypotheses are examined, the chance of at least one apparently unusual result can increase. Without a stated approach, readers cannot determine whether the reported secondary p-values were intended as confirmatory or exploratory.

The registry does not post a comparative analysis for the primary endpoint. For the secondary continuous outcomes, the displayed comparisons are unadjusted re-calculations from posted summary statistics, and no sponsor-reported analyses are listed. The record does not state whether any analysis was adjusted for baseline characteristics, procedural factors, or other variables.

Missing-data methods and analysis populations are also not reported in the registry record. The enrollment figure is 191, while the primary outcome lists 94 participants per arm. The record does not explain the relationship between these figures, state whether any participants were excluded from outcome summaries, or describe how unavailable observations were handled. It does not identify whether the results use all randomized participants, participants with observed outcomes, or another population.

Interim analyses are not reported in the registry record. The sample-size justification and the trial’s own design assumptions are also not reported. The planning illustrations displayed elsewhere on the page are based on observed effects and should not be mistaken for the protocol’s original sample-size calculation. These gaps limit assessment of the analysis choices and of how the posted results relate to the trial’s planned objectives.

11. 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.

The registry safety table records zero serious adverse events among 94 participants at risk in the Amitiza arm and zero among 94 at risk in the placebo arm. It also records zero other adverse events among the participants at risk in each arm. The table does not list serious-event terms.

These entries should be read as the event counts posted for the listed categories and groups. They are not proof that no symptoms or events occurred in the study, and they do not describe event severity beyond the categories shown. The registry does not report death counts, so those cannot be characterized from this record. It also does not provide further detail about the safety observation period or event-collection procedures.

With no events recorded in these categories, the table offers limited information for comparing safety between the arms. A zero count does not establish equivalence or rule out events that are uncommon, unrecorded, or outside the reported categories. These figures are a description of the registry entry, not a standalone safety conclusion.

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

The posted primary outcome shows lower average Ottawa scores in the Amitiza arm than in the placebo arm. Since the registry describes lower scores as indicating better bowel preparation, this is a descriptive pattern in favor of lower scores for the lubiprostone group. The posted full ranges also show that observed scores varied within both groups.

That pattern does not answer every statistical question. The registry does not report a primary treatment-effect estimate, confidence interval, or p-value, and therefore does not show the precision of the between-arm contrast. The arm means alone cannot determine how likely the observed difference is to reflect a systematic group difference rather than sampling variability. Nor do the means establish the importance of any difference for the conduct or outcome of colonoscopy.

The secondary outcomes add information about satisfaction and procedure time, but their unadjusted comparisons have less weight than a prespecified primary analysis, particularly when the registry does not report a multiplicity plan. The record also does not report a comparative analysis for the number of polyps detected. Results from these distinct outcomes should not be combined into a broad claim about overall benefit.

The registry’s enrollment and outcome counts are not reconciled, and its missing-data and analysis-population methods are not reported. These omissions limit understanding of who contributed to the summaries. The safety table records no serious or other adverse events in the listed groups, but it does not establish the absence of all possible events.

In short, the registry supports a description of the posted scores and secondary summaries, not a definitive statistical conclusion about the primary comparison. It does not establish that one preparation is clinically superior, nor does it show that the groups are equivalent. Such conclusions would require information and analyses that are not reported in the registry record.

13. Why This Trial Matters Statistically

This trial is statistically instructive because it separates descriptive results from comparative inference. The primary outcome table presents arm means and full ranges, which reveal the observed score summaries. But a reader also needs a treatment-effect estimate and its uncertainty to judge how precisely the groups differ. Those primary comparative results are not reported in the registry.

The endpoint itself illustrates why outcome summaries need context. The Ottawa score is bounded and combines several ratings, while lower values indicate better preparation. A mean provides a compact summary, but does not show the distribution of individual scores or how each component contributed. Reporting only the mean and full range leaves important features of the outcome distribution unknown.

The trial also makes the distinction between a trial’s original design and later planning illustrations important. The posted sample-size calculations use observed effects to illustrate future study planning. They are not the trial’s sample-size justification and do not represent observed power. Because the registry does not report its own design assumptions, the illustrations cannot fill that gap.

Finally, multiple secondary endpoints, absent analysis-population details, and unreported missing-data methods all affect how confidently results can be interpreted. The calculated secondary comparisons can be useful for understanding the posted summaries, but they are unadjusted and are not listed as sponsor-reported analyses. This is a useful example of why numerical results should be read alongside the completeness of the analysis record, not in isolation.

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 principal limitation in interpreting this trial from the registry is that the primary endpoint is posted only as arm-level mean and full-range summaries. A primary comparative estimate and uncertainty interval are not reported, and no primary analysis is listed. The posted summaries therefore do not quantify the precision of the between-group contrast.

The registry reports enrollment of 191, whereas the primary outcome lists 94 participants in each arm. It does not explain this difference or identify the analysis population. Missing-data handling, exclusions, and the availability of outcome measurements are not reported. These omissions prevent readers from tracing how the reported outcome counts arose.

The record does not include the trial’s sample-size justification, complete analysis plan, handling of multiplicity, or any interim analyses. It also does not report comparative analyses for every secondary outcome. The recalculated secondary comparisons are unadjusted estimates from posted summary statistics, not sponsor-reported analyses. They should be interpreted with that distinction in mind.

The primary outcome’s full range shows only the observed endpoints, not the distribution of scores. No component-level Ottawa results are posted here, so the group summaries cannot show whether particular colon sections or fluid ratings drove the overall score pattern. Finally, the safety table contains zero counts in its listed categories, but the registry does not provide further safety collection detail or death counts. These limitations apply to interpretation of this record and do not, by themselves, determine the underlying trial results.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Split Dose Golytely With Amitiza Pretreatment Versus Split Dose Golytely Plus Placebo in Outpatient Colonoscopy — NCT00611442.
• Registry record last updated 2012-11-01; status last verified 2012-10.
• Results first posted 2012-11-01.
• 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

The registry describes a completed, randomized, double-blind, parallel-group trial of lubiprostone pretreatment versus placebo before split-dose PEG bowel preparation without dietary restrictions for outpatient colonoscopy. The primary outcome was overall bowel cleanliness measured during colonoscopy using the Ottawa bowel preparation scale.

The primary results list 94 participants per arm and report mean scores of 4.8 for Amitiza and 6.2 for placebo, with full ranges of 3.0 to 10.0 and 3.0 to 12.0, respectively. No primary comparative analysis is listed. Secondary outcomes include patient satisfaction, procedure time, and polyps detected. The registry does not report the trial’s analysis plan, sample-size justification, missing-data approach, or analysis population.