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 Omnipaque Versus Gastroview as Oral Contrast for Abdominal and Pelvic CT (NCT00478556), a randomized phase 4 study. The primary outcome is Preferred Contrast Agent.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT00478556 |
| Phase | Phase 4 |
| Condition | Healthy |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | Triple |
| Enrollment | 300 |
| Arms in the primary outcome | n/a |
| Lead sponsor | University of Alabama at Birmingham |
| Results posted | Yes |
2. Clinical Question
Population
The registry lists the condition as healthy and describes patients scheduled by their health care provider for routine abdominal and pelvic CT. The primary outcome was analyzed per protocol. Further eligibility criteria and details about who entered the analysis are not reported in the registry record.
Intervention
One trial arm received Omnipaque as oral contrast. The registry identifies it as a drug intervention. Details such as the administered dose and preparation procedure are not reported in the registry record.
Comparator
The comparison arm received Gastroview as oral contrast. The trial was randomized, with a parallel-group model. Further details about how the random assignment was generated or concealed are not reported in the registry record.
Primary question
The main question was whether participants preferred Omnipaque, Gastroview, or neither after a taste test. The primary outcome timeframe was 1 Day. The registry also identifies bowel opacification score as a secondary outcome, but does not report its result.
3. Trial Design
NCT00478556 is a completed Phase 4 randomized trial sponsored by the University of Alabama at Birmingham. It compared two oral contrast agents for abdominal and pelvic CT: Gastroview and Omnipaque. The study used a parallel-group model, meaning the registry describes separate arms for the two agents rather than a crossover comparison. The record identifies masking as triple, but does not say which roles or people were masked; that information is not reported in the registry record.
The registry records enrollment of 300. The study start is listed as 2007-08 and primary completion as 2009-03. The status is completed. These dates describe the registry timeline, not necessarily the dates of every participant’s treatment or follow-up.
The stated primary objective was to determine whether patient preference differed between the agents. The taste-test responses could be Omnipaque, Gastroview, or neither. Bowel opacification score was identified as a secondary outcome, with no further description of its scale, scoring process, or analysis reported in the registry record.
The primary outcome population is described as per protocol. The criteria defining that population, exclusions from it, and the number analyzed in each arm are not reported in the registry record. The registry does not report the randomization procedure, allocation concealment, the protocol’s sample-size justification, or the detailed statistical plan. These omissions limit how fully the conduct and analysis can be assessed from the 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 | Gastroview Group | Omnipaque Group |
|---|---|---|
| STARTED | 151 | 149 |
| COMPLETED | 151 | 149 |
| NOT COMPLETED | 0 | 0 |
Analysis population for the primary outcome, as defined in the registry: Analysis was per protocol
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 | Gastroview | Omnipaque | Total |
|---|---|---|---|---|
| Participants analysed | 151 | 149 | 300 | |
| Age, Categorical: <=18 years | Participants | 0 | 0 | 0 |
| Age, Categorical: Between 18 and 65 years | Participants | 111 | 96 | 207 |
| Age, Categorical: >=65 years | Participants | 40 | 53 | 93 |
| Age, Continuous | years | 56 (SD 15) | 57 (SD 15) | 57 (SD 15) |
| Sex: Female, Male: Female | Participants | 60 | 56 | 116 |
| Sex: Female, Male: Male | Participants | 91 | 93 | 184 |
| Region of Enrollment: United States | participants | 151 | 149 | 300 |
6. Primary Endpoint
The registry lists the primary outcome as Preferred Contrast Agent, measured over 1 Day.
| Element | Registry entry |
|---|---|
| Result type | Number |
| Measure of spread | not applicable |
| Unit | participants |
| Endpoint classification | Binary Endpoint |
The primary endpoint is titled Preferred Contrast Agent. It measures participants’ stated preference in a taste test, with the available responses described as Omnipaque, Gastroview, or neither. The timeframe is 1 Day, and the endpoint unit is participants. The registry says the analysis was per protocol.
Preference is a patient-reported outcome: it captures which preparation a participant favors rather than a radiologic measurement of bowel appearance. Such an outcome can be useful when the research question concerns acceptability or the experience of taking an oral preparation. It addresses a different question from whether the agent produces a particular degree of bowel opacification. The latter is listed separately as a secondary outcome.
The registry record does not report the number of participants choosing each response, an estimated between-group contrast, or a measure of uncertainty for preference. It also does not report further details about how the taste test was administered, whether participants could distinguish the agents, or how responses were handled in the statistical analysis. Those details matter for interpreting a preference endpoint, but cannot be established from the available record.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry identifies a clear comparison and a patient-centered primary outcome, but it does not report the primary outcome results. In particular, the counts choosing Omnipaque, Gastroview, or neither are not reported in the registry record. Without those counts or an analyzed contrast, the direction and size of any difference in preference cannot be described. No conclusion about which agent participants favored, or whether preferences were similar, can be drawn from the registry information.
The record also does not report the result for bowel opacification score. It names that outcome as secondary, but provides no score values, group comparison, or measure of precision. Consequently, the available information does not establish whether bowel opacification differed between the groups or how precise an estimate might have been.
Enrollment is recorded as 300, but that figure alone does not establish how many participants contributed to either endpoint. The primary analysis is described as per protocol, while group-specific analysis counts and the reasons for any exclusions are not reported in the registry record. An enrolled population and a per-protocol analysis population are not necessarily identical; the record does not allow their relationship to be assessed.
For a treatment comparison, an effect estimate describes the observed difference between groups, while a confidence interval describes the range of values compatible with the data under the analysis assumptions. Neither an effect estimate nor a confidence interval for the primary outcome is reported in the registry record. A significance test result is also not reported. This is an absence of posted results, not evidence that the groups were equal or that a difference was absent.
The record lists no serious adverse events and no other adverse events in either arm among the participants at risk recorded for those categories. These entries are descriptive safety figures; the missing outcome results and limited safety detail do not support broader conclusions about comparative safety. Death counts are not reported in the registry record.
Overall, the registry supports describing the design, outcomes, and recorded adverse-event counts. It does not support a numerical estimate of preference or bowel opacification differences. Readers should distinguish the trial’s stated questions from results that the record does not report.
9. Statistical Methods Explained
Randomization is a method for assigning participants to study groups by chance. In general, this approach aims to reduce systematic differences between groups at the time of assignment, so that outcome comparisons are less vulnerable to confounding. The registry identifies this trial as randomized, but the sequence-generation method, allocation concealment, and any procedures for balancing characteristics are not reported in the registry record. The label alone does not show how the assignment process was implemented.
What does a parallel-group design mean?
In general, a parallel-group design assigns participants to a group that receives one study intervention and compares its outcomes with those in another group. The registry identifies Gastroview and Omnipaque arms and a parallel model. It does not describe the dosing schedule, the duration of exposure, or other care participants received. Those details are not reported in the registry record.
What does triple masking tell us?
Masking is intended to limit the influence of knowledge about treatment assignment on study conduct or outcome assessment. The record labels masking as triple, but does not specify which people or roles were masked, how masking was maintained, or whether it was successful. The label therefore describes the registry’s stated design category, not a complete account of masking procedures.
How should a preference endpoint be analyzed?
In general, an outcome with several response categories can be summarized by the number of participants in each category and compared across groups using an analysis suited to categorical data. The registry lists three possible responses: Omnipaque, Gastroview, or neither. It does not report the category counts or the method used to compare them. The outcome is described as participants, but the record does not state whether the analysis treated the categories as a single multinomial outcome, made selected category comparisons, or used another approach. Those distinctions affect what a reported estimate would mean.
Statistical uncertainty is commonly expressed with a confidence interval. In general, the interval communicates the range of effect values compatible with the observed data and the method’s assumptions; it is not a guarantee that the true effect lies within that range. A significance test addresses a different question, often assessing compatibility with a specified no-difference hypothesis. The registry record does not report a confidence interval, test statistic, or p-value for the primary outcome, so no such inference can be evaluated.
Why can over-dispersion matter?
In general, over-dispersion occurs when observed variability exceeds what a statistical model assumes. If a model understates variability, its uncertainty estimates can be too narrow and tests can appear more decisive than the data warrant. The posted information does not identify a count model or report a dispersion assessment. This is a general statistical consideration, not a claim that over-dispersion occurred in this trial.
What does per-protocol analysis imply?
A per-protocol analysis generally focuses on participants who meet specified conditions for following the study protocol. The registry uses that label for the primary outcome, but does not report the criteria, exclusions, group-specific analysis counts, or how departures from protocol were handled. Per-protocol results can be affected by differences between participants who remain eligible for analysis and those who do not. Without the criteria and participant flow, the extent of that concern cannot be judged. The registry also does not report whether an intention-to-treat analysis was performed.
How should planning illustrations be understood?
A sample-size planning illustration is a hypothetical calculation for a future study under stated assumptions, not a measure of the strength of evidence in the completed trial. The registry’s description says the illustration uses the observed effect, a two-sided significance level of 0.05, equal allocation, and a normal approximation, with the effect to detect set as a stated fraction of the observed effect. It also distinguishes participants per arm for non-time-to-event outcomes from total events for time-to-event outcomes. These planning assumptions do not supply the missing trial outcome results, and the illustration is not observed power. The protocol’s own sample-size justification is not reported in the registry record.
More broadly, an analysis is interpretable only when the outcome definition, analysis population, estimates, and uncertainty are sufficiently described. Some of those elements are identified, including the primary outcome, its timeframe, and the per-protocol label. The actual estimates and important analytical details are not reported in the registry record. Statistical methods can explain what would be needed for interpretation, but cannot recover results that the record does not state.
10. Multiplicity, Missing Data and Analysis Populations
Multiplicity arises when a study assesses several outcomes, response categories, comparisons, or analyses. In general, conducting many statistical tests can increase the chance of finding at least one apparently notable result by chance. The registry identifies a primary preference outcome and bowel opacification score as a secondary outcome. It does not report whether there were additional planned outcomes, how many statistical comparisons were made, or whether any adjustment for multiple testing was planned or used. Those details are not reported in the registry record, so the effect of multiplicity on interpretation cannot be assessed.
The primary endpoint has several possible categories, but the record does not explain how these categories were handled in the analysis or whether category-specific comparisons were prespecified. The listed outcome and analysis counts do not by themselves establish the number of statistical tests or the analysis strategy.
Missing-data handling is also unclear. The registry does not report the number of missing preference responses, reasons for missingness, imputation methods, or sensitivity analyses. It does not report whether participants who did not complete the taste test were included in any analysis. The per-protocol label does not resolve these questions.
Analysis populations are relevant because the record states that the primary outcome was analyzed per protocol, but does not give the criteria or group-specific numbers analyzed. It does not report whether an intention-to-treat analysis was conducted or whether results differed across analysis populations. These gaps limit assessment of attrition, selection into the analysis, and robustness of the findings.
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 |
|---|---|---|---|
| Gastroview | 0 | 151 | 0.0% |
| Omnipaque | 0 | 149 | 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 |
|---|---|
| Gastroview | 0 of 151 |
| Omnipaque | 0 of 149 |
For Gastroview, the registry records 0 serious adverse events among 151 participants at risk for that category, and 0 other adverse events among 151 at risk. For Omnipaque, it records 0 serious adverse events among 149 participants at risk and 0 other adverse events among 149 at risk. These are registry-reported counts for the categories shown; they should not be interpreted as proof that no adverse effects occurred outside the recorded categories or reporting period.
The timeframe and methods used to collect adverse-event information are not reported in the registry record. The record does not list any serious adverse-event terms. Death counts are not reported in the registry record. These figures are descriptive and do not provide a comparative risk estimate or an uncertainty interval. They also do not establish that the agents have identical safety profiles. Interpreting safety requires attention to event definitions, follow-up, ascertainment, and the amount of information available, details that are not reported in the registry record.
12. What the Result Does, and Does Not, Mean
The trial’s stated primary question concerns patient preference between Omnipaque and Gastroview as oral contrast for abdominal and pelvic CT. The registry also identifies bowel opacification score as a secondary outcome. These objectives describe what the study set out to assess; they are not, by themselves, evidence about the direction or magnitude of a result.
The registry record does not report the primary preference counts or a statistical comparison. It also does not report the bowel opacification scores or their comparison. Accordingly, the posted information cannot establish a preference advantage, equivalence, or absence of difference. It cannot establish whether bowel opacification differed or how precisely a difference was estimated. Lack of a reported result should not be treated as a null finding.
The enrollment figure, design labels, and outcome definitions give useful context, but do not substitute for outcome estimates and their uncertainty. The per-protocol designation also means that assessment of the primary analysis requires information about its eligibility criteria and participant flow, which are not reported in the registry record.
The safety entries record no serious or other adverse events in the listed at-risk groups. These counts do not answer the primary preference question and should not be treated as comprehensive evidence of comparative safety. Details about safety ascertainment and deaths are not reported in the registry record.
The defensible interpretation is therefore limited: a completed randomized, parallel-group comparison was registered, with patient preference as the primary outcome and bowel opacification score as a secondary outcome, but the outcome results needed to evaluate those questions are not reported in the registry record. No conclusion about which contrast agent is preferable or about clinical consequences follows from the available results information.
13. Why This Trial Matters Statistically
This trial raises a useful statistical distinction between the question a study asks and the evidence needed to answer it. Patient preference and bowel opacification are different kinds of outcomes. A preference response captures a participant’s stated choice, while a bowel opacification score concerns an imaging assessment. Each requires a clear definition, appropriate analysis, and reported results for interpretation.
The preference endpoint has several possible responses rather than a simple description of which group received which agent. That structure makes it important to know how responses were counted and compared. A report of category counts, an effect estimate, and its uncertainty would allow readers to assess both the pattern of preferences and the precision of the comparison. Those results are not reported in the registry record.
The per-protocol label is another important statistical feature. It identifies an analysis population, but the meaning of that population depends on the criteria and participant flow. Without those details, readers cannot assess whether exclusions or missing responses could have influenced the observed comparison. Clear reporting of analysis populations is essential for judging how randomized assignment relates to the analyzed results.
The record also illustrates why safety counts and efficacy or preference outcomes must be read separately. Zero recorded events in the listed adverse-event categories describe those entries; they do not answer the primary question or replace a detailed safety assessment. Finally, planning calculations are not evidence about observed outcomes. They depend on assumptions and cannot fill gaps in a registry record’s result reporting.
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 main limitation for interpretation is that the registry record does not report the primary preference results. It provides no response counts, effect estimate, confidence interval, or test result. The secondary bowel opacification outcome is named, but its scoring details and results are not reported in the registry record. This prevents assessment of the trial’s stated outcome questions.
Important design and analysis details are also absent. The record does not explain random-sequence generation or allocation concealment, specify which roles were masked, or describe the administration of the taste test. It does not define the per-protocol population, report the number analyzed in each arm, or explain missing-response handling. These omissions limit evaluation of bias and analysis robustness.
The bowel opacification score’s scale, assessor procedures, and analysis are not reported in the registry record. Details of adverse-event ascertainment and the timeframe for safety reporting are also not reported. Death counts are not reported in the registry record.
The registry records enrollment of 300, but does not provide participant flow or clarify how enrollment relates to the analysis populations. The protocol’s sample-size justification and detailed statistical plan are not reported in the registry record. These limitations do not establish that the trial was poorly conducted; they identify what cannot be evaluated from the registry information.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Omnipaque Versus Gastroview as Oral Contrast for Abdominal and Pelvic CT — NCT00478556.
- Registry record last updated 2017-04-18; status last verified 2017-03.
- Results first posted 2010-06-11.
- 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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Use this trial's endpoint as a starting point for deeper study of effect measures, confidence intervals, and sample-size planning.
18. Record Summary
NCT00478556 is a completed Phase 4 randomized, triple-masked, parallel-group trial sponsored by the University of Alabama at Birmingham. It compared Gastroview with Omnipaque as oral contrast for abdominal and pelvic CT. Enrollment is recorded as 300, with study start listed as 2007-08 and primary completion as 2009-03.
The primary outcome was participant preference in a taste test, with possible responses of Omnipaque, Gastroview, or neither, assessed at 1 Day. The primary analysis population is described as per protocol. Bowel opacification score is listed as a secondary outcome. Results for both outcomes are not reported in the registry record. The safety entries record 0 serious and 0 other adverse events in each arm’s listed at-risk group; deaths are not reported in the registry record.