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 Improving Bowel Preparation for Colonoscopy With a Simple Educational Card (NCT00643682), a randomized na study. The primary outcome is Boston Bowel Preparation Scale Score.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT00643682 |
| Phase | NA |
| Condition | Colonic Polyps, Colonic Neoplasms |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | Single |
| Enrollment | 2000 |
| Arms in the primary outcome | 2 |
| Lead sponsor | Boston Medical Center |
| Results posted | Yes |
2. Clinical Question
Population
Patients scheduled for colonoscopy in a study concerning colonic polyps and colonic neoplasms. The registry record does not provide further eligibility details or a fuller description of the population included in the primary outcome results.
Intervention
An educational card added to standard pre-endoscopy instructions. The registry record describes the card as a simple educational aid but does not provide its full content or describe how it was delivered.
Comparator
Standard pre-endoscopy instructions without the educational card.
Primary question
Does adding the educational card change the quality of bowel preparation for colonoscopy, as assessed using the Boston Bowel Preparation Scale? The posted results report the scale’s median and inter-quartile range in each group, but no inferential comparison.
The trial addresses an educational and procedural question: whether an additional instruction aid is associated with a different bowel-preparation score than standard instructions alone. The primary measure is an ordinal scale, with higher scores representing a cleaner colon. The posted group summaries are identical: the median score is 6 in both groups, and each group has an inter-quartile range from 6 to 7. These summaries describe the center and middle spread of the observed scores; they do not establish whether the full score distributions were alike or whether any group difference was statistically detectable.
The registry lists secondary outcomes concerning colonoscope advancement time, withdrawal time, and the number of repeat procedures recommended because of inadequate preparation. Results for those outcomes are not reported in the registry record. The record also does not describe the trial’s eligibility criteria in enough detail to characterize which patients the findings may represent.
3. Trial Design
The registry describes a randomized, single-masked, parallel-group trial. One group received an educational card in addition to standard pre-endoscopy instructions; the control group received standard instructions alone. The registry does not identify which participants or study personnel were masked, nor does it provide further detail about the randomization process, allocation concealment, or how adherence to the assigned instructions was assessed.
The recorded enrollment is 2000, and the status is completed. The posted primary outcome results include 477 participants in the Educational Card group and 492 in the Control group. These are the group counts attached to the reported primary outcome summaries. The registry record does not explain the relationship between those counts and total enrollment or report reasons why participants may not appear in the primary outcome results.
The sponsor is Boston Medical Center. The recorded study start is 2006-02, and primary completion is 2008-06. The primary outcome is the Boston Bowel Preparation Scale score, with a listed timeframe of 2 years. The record does not further explain the timing of score assessment within that timeframe.
The listed design is parallel, meaning that the groups are compared as separate assigned arms rather than as repeated treatment periods for each participant. The registry classifies the study as randomized and single-masked, but the operational details needed to evaluate those features are not reported in the registry record. In particular, the record does not describe whether outcome assessors knew group assignment, how the card was distributed, or whether the standard instructions were uniform across participants.
The registry lists three secondary outcomes: time to advance the colonoscope from anus to cecum, time to withdraw it from cecum to anus, and the number of repeat procedures recommended because of inadequate bowel preparation. Although the record lists four outcome measures overall, no analysis results are posted for those secondary outcomes. The recorded count of posted analyses is zero; this means the registry contains no posted analysis results, not that no analyses were conducted.
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 | Educational Card | Control |
|---|---|---|
| STARTED | 999 | 1001 |
| COMPLETED | 477 | 492 |
| NOT COMPLETED | 522 | 509 |
Reasons for not completing this period:
| Reason | Educational Card | Control |
|---|---|---|
| did not keep appointment | 522 | 509 |
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 | Educational Card | Control | Total |
|---|---|---|---|---|
| Participants analysed | 477 | 492 | 969 | |
| Age Continuous | years | 57 (SD 8) | 57 (SD 7) | 57 (SD 8) |
| Sex: Female, Male: Female | Participants | 279 | 287 | 566 |
| Sex: Female, Male: Male | Participants | 198 | 205 | 403 |
| Region of Enrollment: United States | participants | 477 | 492 | 969 |
6. Primary Endpoint
The registry lists the primary outcome as Boston Bowel Preparation Scale Score, measured over 2 years.
| Element | Registry entry |
|---|---|
| Result type | Median |
| Measure of spread | Inter-Quartile Range |
| Unit | units on a scale |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint is the Boston Bowel Preparation Scale score. The registry describes it as an ordinal scale ranging from 0, fully unprepared colon, to 9, perfectly clean colon. Higher values represent a better outcome. Its purpose is to give a structured rating of bowel cleanliness in the setting of colonoscopy, so preparation quality can be described across the trial groups.
The endpoint is reported as a median with an inter-quartile range. A median identifies the middle of an ordered set of scores; it does not require treating the scale as if the distance between every pair of adjacent values were identical. The inter-quartile range describes the middle portion of the observed scores, from the lower quartile to the upper quartile. It gives information about spread around the median but does not show every score or the shape of the full distribution.
For the Educational Card group, the posted median is 6 and the inter-quartile range is 6 to 7. For the Control group, the median is also 6 and the inter-quartile range is also 6 to 7. These summaries offer a compact description of preparation scores, but they do not indicate how many participants had each score, whether distributions differed in other ways, or how precise a comparison between groups would be. No confidence interval or inferential test for the primary outcome is reported in the registry record.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The posted primary outcome summaries have the same central value and middle spread in both groups. The median Boston Bowel Preparation Scale score is 6 in the Educational Card group and 6 in the Control group. The inter-quartile range is 6 to 7 in each group. On the basis of these summaries alone, there is no visible separation between the groups in the reported median or inter-quartile range.
This descriptive similarity should not be treated as a formal finding of equivalence or as proof that the groups had identical outcomes. A median and inter-quartile range compress the distribution into a few features. They do not show the frequency of each score, the tails of the distributions, or how individual participants’ scores compare. A formal comparison would ordinarily include an estimate of the between-group contrast and a measure of its uncertainty, such as a confidence interval, along with an inferential procedure appropriate to the outcome and design. Such results are not reported in the registry record.
The primary outcome results are associated with 477 participants in the Educational Card group and 492 in the Control group. The registry’s overall enrollment is 2000. The record does not explain the difference between total enrollment and these outcome group counts, so the reasons and implications of that difference cannot be determined from the posted information. In particular, the record does not report missing outcome counts, exclusions from analysis, or the analysis population definition.
The three listed secondary outcomes concern procedural timing and repeat procedures recommended because of inadequate preparation. Their results are not reported in the registry record. The record therefore does not support a statistical interpretation of those outcomes or a comparison of their patterns with the primary score.
The registry reports no posted analysis results. That is distinct from evidence that no analysis was performed. It means the record does not provide a sponsor analysis, statistical test, confidence interval, adjusted estimate, or account of the analysis model for the primary outcome. The posted summaries can be read descriptively, but they do not establish statistical significance, clinical importance, or the precision of a treatment contrast.
General: An interval estimate is useful because it presents a range of values compatible with the data and analysis assumptions, rather than only a point estimate. Without such an estimate, readers cannot judge how much uncertainty surrounds a between-group difference. Likewise, the absence of a reported test does not allow a conclusion about whether a prespecified statistical threshold was or was not crossed.
9. Statistical Methods Explained
The registry identifies a randomized, single-masked, parallel-group design and reports the primary outcome as a median with an inter-quartile range. It does not report the sponsor’s statistical analysis plan or an analysis result. The distinction between design information and analysis information matters: knowing the groups were randomized does not reveal which statistical procedure was used, how missing outcomes were handled, or how uncertainty in the comparison was quantified.
Why report a median and inter-quartile range?
General: A median is appropriate for describing an ordered outcome because it identifies the central position of the observed values without requiring the score to behave like a continuous measurement with equal spacing between all adjacent values. The inter-quartile range gives the lower and upper quartiles and describes the spread of the middle part of the data. These summaries can be informative when a distribution is asymmetric or when values are naturally ordered categories.
For this outcome, the registry describes the scale as ordinal and gives the meaning of its endpoints. A median of 6 and an inter-quartile range of 6 to 7 in each group convey that the reported center and middle spread coincide. They do not reveal the score counts, the distribution beyond the middle range, or whether a small group of unusually low or high scores affected another feature of the data.
What would a group comparison add?
General: A statistical comparison estimates how the groups differ and quantifies uncertainty around that estimate. The appropriate method depends on the outcome’s scale, the trial design, the analysis objective, and the assumptions judged reasonable for the data. A method for comparing ordinal outcomes may use ranks or a model that recognizes the ordering; other choices may target a different feature of the distributions. The registry record does not state which method was planned or used, so no method can be attributed to the trial.
A confidence interval would describe uncertainty around a specified contrast under the assumptions of the analysis. A hypothesis test would assess compatibility with a null hypothesis under its own assumptions. Neither result is reported. The identical medians and inter-quartile ranges do not substitute for either an interval estimate or a test, and a formal test alone would not communicate the full size or practical relevance of a contrast.
Randomization, masking, and analysis
General: Random assignment is intended to make treatment groups comparable on average with respect to both measured and unmeasured baseline characteristics. It does not guarantee that the realized groups are exactly alike, and it does not resolve missing outcome information. Masking can reduce some forms of behavior or assessment influenced by knowledge of assignment, but the registry’s single-masked label does not say who was masked. Allocation concealment and implementation details are not reported in the registry record.
Analysis populations also matter. An analysis based on assigned groups generally preserves the randomized comparison, whereas analyses restricted to participants with particular follow-up or adherence patterns can answer a different question and may be vulnerable to bias. The registry does not identify the population used for the posted summaries or explain how participants without an observed score were treated.
Planning illustrations and observed power
The registry’s sample-size assumptions describe planning illustrations based on the observed effect, using a two-sided significance level of 0.05, equal allocation, and a normal approximation. The stated effect to detect is a fraction of the observed effect. The assumptions distinguish participant counts per arm for non-time-to-event outcomes from total event counts for time-to-event outcomes. The primary bowel-preparation score is not a time-to-event outcome.
General: Such illustrations ask how many participants a hypothetical study might require under specified assumptions. They depend on the effect chosen for planning and on the statistical approximation. They are not the trial’s own sample-size justification unless the registry identifies them as such; the record does not report that justification. They also are not observed power, which is not a useful replacement for interpreting the estimated effect and its uncertainty after a trial. No numerical planning counts or effect fractions are reported in the registry record.
Over-dispersion and model fit
General: Over-dispersion occurs when observed variability is greater than a statistical model expects. If it is ignored in a setting where it is present, uncertainty estimates can be too small. Whether over-dispersion is relevant depends on the chosen model and data structure. The registry does not report a model for the primary score, a dispersion assessment, or any model diagnostics; therefore, no conclusion about over-dispersion or model fit is possible for this trial.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists the primary Boston Bowel Preparation Scale score and three secondary outcomes: time to advance the colonoscope, time to withdraw it, and repeat procedures recommended because of inadequate bowel preparation. It reports four outcome measures overall, but no analyses are posted. Results for the secondary outcomes are not reported in the registry record.
Multiplicity arises when several outcomes or comparisons are examined, because considering multiple statistical tests can raise the chance of at least one apparently noteworthy result under a set of null hypotheses. General: A prespecified hierarchy, a multiplicity adjustment, or a clearly defined primary outcome can help explain how multiple outcomes are interpreted. The registry identifies a primary outcome, but does not report whether a hierarchy, adjustment, or other multiplicity strategy was planned or used. No claim about multiplicity control can therefore be made.
The record provides group counts for the primary outcome summaries, but it does not report missing outcome counts, reasons for missingness, or the handling of participants without a score. It also does not define the analysis population. Without those details, the completeness of outcome ascertainment and the relationship between enrollment and the analyzed group summaries cannot be assessed from the registry record.
General: Missing-data methods rely on assumptions about why values are absent and how missingness relates to observed or unobserved outcomes. Different assumptions can yield different estimates. Reporting the amount and pattern of missingness, as well as the analysis population and sensitivity analyses, helps readers understand the robustness of a result. Those details are not reported in the registry record.
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 |
|---|---|---|---|
| Educational Card | 0 | 477 | 0.0% |
| Control | 0 | 492 | 0.0% |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 0% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Educational Card | 0 of 477 |
| Control | 0 of 942 |
The registry reports zero serious adverse events among 477 participants at risk in the Educational Card group and among 492 participants at risk in the Control group. It also reports zero other adverse events in the listed groups. For other adverse events, the recorded number at risk is 477 for the Educational Card group and 942 for the Control group. That Control denominator differs from the primary outcome group count; the reason is not reported in the registry record.
These entries describe what the registry reports, not proof that no adverse events occurred. The record does not explain how adverse events were collected, what observation period applied, or whether the entries represent complete ascertainment. Death counts are not reported in the registry record. No top serious adverse-event terms are listed.
General: A zero count is most interpretable alongside a clear denominator, defined event criteria, a specified observation period, and information about completeness of reporting. Denominators that differ across outcomes or records need explanation before readers can understand why the counts differ. The adverse-event figures do not provide a comparative safety analysis, and the posted information does not support broader conclusions about safety.
12. What the Result Does, and Does Not, Mean
The posted primary outcome summaries show the same median Boston Bowel Preparation Scale score and the same inter-quartile range in the two groups. The Educational Card group had a median of 6 and an inter-quartile range of 6 to 7; the Control group also had a median of 6 and an inter-quartile range of 6 to 7. This is a descriptive statement about the reported summaries.
It does not establish that the full outcome distributions were identical, that the groups were equivalent, or that a particular difference was ruled out. The registry record contains no posted test, confidence interval, or estimated contrast for the primary outcome. Consequently, the precision of any between-group difference cannot be judged from the registry results. The summaries also do not establish whether any difference would be important in practice.
The record does not report results for the secondary outcomes, including colonoscope advancement time, withdrawal time, or repeat procedures recommended because of inadequate preparation. It also does not explain why the primary outcome group counts are smaller than the recorded enrollment. Missing outcome information, analysis population, and handling of missing data are not reported.
General: Statistical evidence is strongest when the estimated effect, its uncertainty, the analysis population, and the assumptions behind the analysis are all available. Descriptive summaries remain useful, but they answer a narrower question: what were the reported group centers and middle spreads? They cannot by themselves determine whether an intervention caused a difference or whether two approaches can be regarded as equivalent.
The registry describes a randomized comparison of an educational card plus standard instructions against standard instructions alone. The posted data therefore permit a limited account of the primary outcome summaries and the recorded adverse-event counts. They do not provide a complete statistical assessment of effectiveness, secondary outcomes, missingness, or safety.
13. Why This Trial Matters Statistically
This trial illustrates why a registry entry’s design description and its results must be read separately. Randomization and a parallel-group comparison describe how the trial was organized, while the posted outcome summaries describe only selected features of the observed scores. The registry identifies a clinically interpretable primary measure, but does not post an inferential comparison for it.
The primary measure is ordinal, and the registry reports medians and inter-quartile ranges rather than means and standard deviations. That choice communicates the ordered nature of the scale and gives a compact account of its center and middle spread. At the same time, identical summaries can conceal other distributional differences. Readers need the full analysis or additional distributional information to assess those possibilities.
The difference between recorded enrollment and the primary outcome group counts also makes transparent reporting important. Without a participant flow, missingness information, or an analysis-population definition, readers cannot tell why the reported counts are what they are. This limits assessment of how representative the summaries are of enrolled participants and how much missing outcome information may matter.
Finally, the registry lists several secondary outcomes, yet does not post analyses for them. Multiple outcomes make prespecified analytic priorities and transparent reporting especially useful. The record identifies a primary endpoint, but does not report a multiplicity approach or a statistical analysis plan. These absences do not show that the trial was poorly conducted; they limit what can be evaluated from the registry record.
14. Limitations
- The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
- Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.
The registry record does not provide a detailed description of eligibility criteria, participant characteristics, or the setting beyond identifying Boston Medical Center as sponsor. This limits assessment of how closely the observed group summaries may apply to other patient populations or clinical settings.
Although the design is recorded as randomized and single-masked, the record does not describe the randomization sequence, allocation concealment, who was masked, or whether outcome assessment was masked. It also does not describe the educational card’s content, delivery, or adherence. These details are relevant to understanding how the intervention and comparison were implemented.
The primary outcome summaries include 477 participants in the Educational Card group and 492 in the Control group, while recorded enrollment is 2000. The registry does not explain this relationship, report participant flow, or describe exclusions and missing outcomes. It does not state the analysis population or the method used to handle missing scores.
No inferential analysis is posted for the primary outcome, and no results are reported for the listed secondary outcomes. The registry does not report an effect estimate, uncertainty interval, statistical test, analysis model, or multiplicity approach. It also does not report the trial’s own sample-size justification. The planning assumptions listed for illustrations are not a substitute for that justification or for analysis results.
Safety reporting has additional interpretive limits: the other-adverse-event denominator recorded for the Control group is 942, unlike the primary outcome group count, and the record does not explain why. Death counts, event collection procedures, and the observation period for adverse events are not reported in the registry record. These limitations restrict interpretation of both the outcome and safety information.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Improving Bowel Preparation for Colonoscopy With a Simple Educational Card — NCT00643682.
- Registry record last updated 2012-10-01; status last verified 2012-08.
- Results first posted 2012-10-01.
- 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.
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18. Record Summary
The registry describes a completed randomized, single-masked, parallel-group trial sponsored by Boston Medical Center. It compared an educational card plus standard pre-endoscopy instructions with standard instructions alone. Recorded enrollment is 2000; the study start is 2006-02 and primary completion is 2008-06.
The primary endpoint is the Boston Bowel Preparation Scale score, an ordinal measure for which higher scores indicate better preparation. The Educational Card group had a median of 6 and an inter-quartile range of 6 to 7 among 477 participants. The Control group had the same median and inter-quartile range among 492 participants.
No analyses are posted in the registry. Results for the three listed secondary outcomes are not reported in the registry record. The record does not describe the analysis population, missing-data handling, or the statistical analysis plan. Serious adverse-event counts are reported as zero in both groups, while other adverse-event counts are also zero with different recorded denominators; death counts are not reported in the registry record.