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 Cap-fitted Colonoscopy: a Randomized, Tandem Colonoscopy Study of Adenoma Miss Rates (NCT00577083), a randomized na study. The primary outcome is Number of Adenomas.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT00577083 |
| Phase | NA |
| Condition | Polyps |
| Allocation | Randomized |
| Design model | Crossover |
| Masking | None (open label) |
| Enrollment | 100 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Indiana University |
| Results posted | Yes |
2. Clinical Question
Population
Participants undergoing tandem colonoscopy to examine the colon for adenomas. The registry record lists 100 enrolled participants, but does not report detailed eligibility criteria, participant characteristics, or the population used in an outcome analysis.
Intervention
Cap-fitted colonoscopy, using a clear plastic hood attached to the tip of the colonoscope. The study description explains that the cap can be pressed against folds or ridges to expose the lining on the other side.
Comparator
Regular colonoscopy without a cap on the end of the colonoscope. The recorded arms are named Initial cap-fitted and Initial regular, describing the method used for the first insertion.
Primary question
Whether cap-fitted colonoscopy changes adenoma detection or the number of adenomas missed, compared with regular colonoscopy, during a tandem examination. The registry lists a primary outcome of number of adenomas, but does not report the numerical results or an estimated treatment contrast.
The clinical rationale in the registry is that polyps may be hidden behind folds and bends in the colon. Its background description says that about 30% of polyps under 5 mm may be missed during colonoscopy. That is background information, not a result from this trial. The study description proposes that a cap might flatten folds and make more of the bowel lining visible.
The question is about detection during colonoscopy, rather than a clinical outcome after treatment or follow-up. The trial is described as randomized, tandem, and crossover, with the first insertion identified as either cap-fitted or regular. The registry record does not give the sequence details, the number of examinations completed by each participant, or a numerical comparison of adenomas detected or missed. Consequently, the clinical question is clear, but the posted record does not establish how the observed findings answered it.
3. Trial Design
The study is registered as a randomized, unmasked crossover trial of cap-fitted colonoscopy. Its title identifies a tandem-colonoscopy design and adenoma miss rates as the central topic. Enrollment is listed as 100. The recorded intervention is cap-fitted colonoscopy, and the two arm descriptions identify the initial examination as either cap-fitted or regular, without a cap.
A tandem design uses repeated examination to assess lesions that may not have been identified during an earlier examination. In general, comparing findings across examinations can help characterize missed lesions. The registry record, however, does not provide the full examination sequence, the interval between examinations, how findings were assigned to each examination, or how the miss rate was calculated. The crossover model is recorded, but details needed to reconstruct the allocation sequence are not reported in the registry record.
The study is listed as completed. Its start is recorded as 2006-11 and primary completion as 2009-10. The sponsor is Indiana University, and the condition listed is Polyps. The phase is recorded as NA. Masking is listed as none, so the registry describes the study as unmasked; it does not explain which people involved in examination, lesion assessment, or analysis knew the assigned method.
The registry record does not report a sample-size justification, target effect, or statistical power calculation used to design the trial. A planning illustration may use an observed effect as a hypothetical input, but such an illustration is not the trial's design rationale and is not observed power. No numerical planning output is stated in the registry record. The record also does not report an interim-analysis plan, stopping rules, or a detailed statistical analysis plan.
The posted record identifies the study question and broad design, but does not provide participant flow, baseline characteristics, adherence to the examination sequence, or the number of participants included in each analysis. Those omissions make it difficult to assess how the randomized design was implemented and how closely the analyzed participants corresponded to the enrolled group.
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.
First Intervention (14 Days)
| Stage | No Cap First, Then Cap-fitted | Initial Cap-fitted First, Then No Cap |
|---|---|---|
| STARTED | 48 | 52 |
| COMPLETED | 48 | 52 |
| NOT COMPLETED | 0 | 0 |
Washout (14 Days)
| Stage | No Cap First, Then Cap-fitted | Initial Cap-fitted First, Then No Cap |
|---|---|---|
| STARTED | 48 | 52 |
| COMPLETED | 48 | 52 |
| NOT COMPLETED | 0 | 0 |
Second Intervention (14days)
| Stage | No Cap First, Then Cap-fitted | Initial Cap-fitted First, Then No Cap |
|---|---|---|
| STARTED | 48 | 52 |
| COMPLETED | 48 | 52 |
| NOT COMPLETED | 0 | 0 |
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 | No Cap First, Then Cap Fitted | Initial Cap-fitted First Then No Cap | Total |
|---|---|---|---|---|
| Participants analysed | 48 | 52 | 100 | |
| Age, Categorical: <=18 years | Participants | 0 | 0 | 0 |
| Age, Categorical: Between 18 and 65 years | Participants | 48 | 52 | 100 |
| Age, Categorical: >=65 years | Participants | 0 | 0 | 0 |
| Sex: Female, Male: Female | Participants | 19 | 24 | 43 |
| Sex: Female, Male: Male | Participants | 29 | 28 | 57 |
| Region of Enrollment: United States | participants | 48 | 52 | 100 |
6. Primary Endpoint
The registry lists the primary outcome as Number of Adenomas, measured over after the second colonoscopy is completed.
| Element | Registry entry |
|---|---|
| Result type | Number |
| Measure of spread | not applicable |
| Unit | First Colonoscopy number of adenomas |
| Endpoint classification | not reduced to a single comparison |
The primary outcome is titled Number of Adenomas, with the unit described as the first-colonoscopy number of adenomas. Its stated timeframe is after the second colonoscopy is completed. This outcome concerns the count of adenomas identified in relation to the first examination after a second examination has taken place. The registry record's description also frames the study around whether cap-fitted colonoscopy may reduce adenoma miss rates, especially for small adenomas.
In general, counting adenomas can describe detection yield, while a miss-rate measure requires an explicit definition of which lesions count as missed and what set of findings supplies the reference. A tandem examination can support such an assessment because findings from a later examination may reveal lesions not identified earlier. The exact endpoint definition, however, is not reported in the registry record. It does not specify the lesion-level matching rules, how adenomas found on each pass were classified, or the denominator used for a miss rate.
The outcome is relevant to the study's stated detection question because it focuses on adenomas rather than examination time alone. Examination time is listed as a secondary outcome, measured with a stopwatch that pauses when a polyp is located and restarts after removal and retrieval. The registry record contains no numerical primary-outcome result, summary statistic, confidence interval, or comparison between the initial cap-fitted and initial regular groups. Thus, the endpoint's intended subject is identifiable, but the magnitude and precision of any observed difference are not reported.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record identifies a randomized, unmasked crossover study with 100 enrolled participants and a primary outcome concerning the number of adenomas. It does not report the numerical outcome data, an effect estimate, a confidence interval, or a statistical test comparing cap-fitted with regular colonoscopy. The record therefore does not support a quantitative conclusion about the direction, size, or precision of any difference in adenoma detection or miss rates.
The primary outcome description says that the first-colonoscopy number of adenomas is assessed after the second colonoscopy is completed. The study's stated purpose is to investigate whether fitting a cap to the colonoscope reduces missed adenomas, particularly small adenomas. These statements describe the intended research question, not the observed answer. The registry's descriptive language about the technology should not be read as a result demonstrating an effect.
For a numerical interpretation, readers would need the reported adenoma counts or miss-rate estimates for each comparison, together with the analysis method and a measure of uncertainty. A confidence interval, in general, communicates the range of effect values compatible with the data and the method used to construct it. Without an estimate and interval, precision cannot be judged. A p-value, if available, would address compatibility with a specified statistical null under model assumptions; it would not by itself describe the size or clinical importance of a difference. No p-value is reported in the registry record.
The crossover and tandem features make the analysis details especially important. In general, a crossover analysis may need to account for measurements from the same participant, and a tandem assessment may require a clear rule for identifying lesions across examinations. The registry record does not state how within-participant dependence, examination order, or lesion matching was handled. It also does not give the allocation sequence or an analysis population. These missing details prevent independent assessment of whether a reported contrast, if one were available elsewhere, would reflect the randomized comparison as intended.
The adverse-event summary lists zero participants at risk and zero affected in both initial groups, while death counts are null. With no participants represented as at risk in those entries, these fields do not provide interpretable incidence estimates or establish that no adverse events occurred. The record does not provide further safety results.
Overall, the registry record supports a description of the study's design and question, but not an estimate of efficacy, detection benefit, or uncertainty. It also does not report enough outcome or analysis information to evaluate whether the study's findings align with its stated aim.
9. Statistical Methods Explained
The study is described as randomized, unmasked, and crossover. Randomization is a method for assigning study conditions by chance; in general, its purpose is to reduce systematic differences between comparison groups at assignment. The registry record does not describe the randomization procedure, sequence generation, allocation concealment, or sequence balance. Those details are therefore not reported in the registry record.
What does the crossover label imply?
In general, a crossover design compares interventions within participants, so each participant may contribute observations under more than one condition. This can account for stable differences between participants, but requires suitable methods for paired or repeated measurements. It can also require consideration of period and carryover effects, depending on how the interventions are sequenced and how outcomes are measured. The registry record labels the model CROSSOVER and describes the initial examination arms, but does not report the complete sequence, period structure, washout or interval details, or a statistical method for repeated observations. No conclusion about how those design features were handled can be drawn from the posted record.
How does tandem examination relate to adenoma misses?
In general, tandem examination allows findings from one examination to be considered alongside findings from another, which can help identify lesions not seen on an earlier pass. A miss-rate outcome requires a defined classification rule: the analysis must identify which lesions were detected on which examination and specify the reference set used to determine that a lesion was missed. For a fair comparison, the rule should be applied consistently across study conditions. The registry record states the goal of studying adenoma miss rates, but does not report the lesion-matching procedure, the exact miss-rate formula, or how disagreements were adjudicated.
What does the primary outcome measure?
The listed primary outcome is Number of Adenomas, with the unit described as the first-colonoscopy number of adenomas and a timeframe after the second colonoscopy is completed. The registry record does not state whether the analysis uses raw counts, a participant-level summary, a lesion-level outcome, or a derived miss-rate measure. Those choices matter because adenoma counts are nonnegative and may vary substantially among participants. In general, count outcomes can be analyzed with methods suited to their distribution; the appropriate method depends on features such as the frequency of zero counts and whether variation exceeds what a chosen model expects. The record does not report the distribution or model used.
What does unmasked mean for interpretation?
The registry lists masking as none. In general, knowledge of the examination method could influence conduct, lesion assessment, or outcome classification, depending on who is aware of the assignment and how outcomes are determined. The registry does not say which people were aware of the method or whether any outcome assessment was independently reviewed. It is therefore not possible to assess the role of masking in measurement from the registry record alone.
What can a confidence interval and p-value tell readers?
In general, a confidence interval describes uncertainty around an estimated effect under the assumptions of the analysis. A narrower interval indicates greater precision than a wider interval, while the interval's location and span help show which effect values remain compatible with the data. A p-value measures how unusual data at least as incompatible with a specified null hypothesis would be under that null and the model assumptions. It does not measure the probability that the null is true, nor does it replace an effect estimate. No effect estimate, confidence interval, or p-value for the primary comparison is reported in the registry record, so these interpretations cannot be applied to an observed result.
How should planning illustrations be read?
The registry describes a planning illustration based on the observed effect, with a two-sided significance level of 0.05, equal allocation, and a normal approximation. For non-time-to-event outcomes, such illustrations are expressed as participants per arm; the stated effect to detect is a fraction of the observed effect. Such calculations are hypothetical planning exercises, not observed power and not evidence that a trial was designed with those assumptions. The registry record does not report the trial's own sample-size justification, nor does it provide a numerical illustration to interpret. No planning quantity can be used to infer the probability that this completed study detected an effect.
More generally, over-dispersion occurs when count data vary more than a particular statistical model expects. If present, a model that ignores it may give uncertainty estimates that are too small. This is a general methodological consideration for count outcomes, not a finding about this study: the registry record does not report a distributional assessment or indicate whether over-dispersion was examined.
10. Multiplicity, Missing Data and Analysis Populations
The registry record does not report a detailed plan for handling multiplicity. It lists a primary outcome of number of adenomas and identifies examination time as a secondary outcome, but does not state whether there were additional outcome definitions, subgroup analyses, or multiple statistical comparisons. In general, testing many outcomes or subgroups can increase the chance of finding at least one apparently notable result by chance. Whether adjustment is appropriate depends on the analysis plan and the claims being made; the record does not provide enough detail to assess this issue.
Missing-data methods and analysis populations are also not reported in the registry record. The record does not state how many enrolled participants completed both examinations, whether all randomized participants were analyzed, how incomplete examinations were handled, or how missing adenoma assessments were addressed. It does not identify an intention-to-treat, per-protocol, or other primary analysis population. These details matter because exclusions or incomplete observations can affect the composition of the analyzed group, particularly in repeated-measure and crossover designs.
The adverse-event fields list zero participants at risk and zero affected in both initial groups, with deaths recorded as null. These entries do not supply usable denominators for safety comparisons. The record does not explain the meaning of the zero-at-risk entries or give a separate account of missing safety observations. It is therefore not appropriate to interpret the entries as proof that no adverse events occurred.
Without an analysis plan, participant flow, missing-data description, and outcome-level results, readers cannot evaluate whether all planned analyses were reported or how incomplete data may have influenced the findings. These are reporting limitations, not evidence that any particular analysis was biased.
11. What the Result Does, and Does Not, Mean
The registry record establishes that a randomized, unmasked crossover study of cap-fitted and regular colonoscopy was completed, with 100 participants enrolled. It identifies adenoma number and miss rates as the central detection concerns and lists examination time as a secondary outcome. These registry entries describe the design and intended measurements.
The record does not report numerical results for adenoma counts, adenoma miss rates, or examination time. It also does not provide an effect estimate, confidence interval, or statistical test for the primary comparison. As a result, the posted information cannot show whether detection differed between methods, how large a difference may have been, or how precise an estimate might be. The description that cap-fitted colonoscopy may reduce missed adenomas is a statement of the study rationale, not evidence of an observed result.
In general, a statistically detectable difference and a clinically important difference are distinct questions. Statistical uncertainty concerns how compatible an estimate is with a range of possible effects under an analysis model. Clinical importance depends on the magnitude and context of the outcome. Since no comparative estimate is reported in the registry record, neither question can be answered from this record.
The registry description calls the study the first North American study of any design and the largest tandem study of cap-fitted colonoscopy, and says that additional study in Western populations is warranted. These are statements in the record's outcome description; they do not supply trial results or substitute for a quantitative comparison. The record does not report participant characteristics that would allow readers to assess how broadly the study population represents other groups.
Accordingly, the record is useful for identifying the research question, intervention, comparator, and broad design, but is insufficient to determine what the study found. It should not be read as demonstrating that either colonoscopy approach had a particular detection advantage or as establishing equivalence between them.
12. Why This Trial Matters Statistically
This trial is statistically interesting because its question concerns lesions that may be missed during an examination, and its design is described as both tandem and crossover. In general, repeated examinations can reveal discrepancies in detection, while crossover comparisons can make within-participant contrasts possible. Those features can be informative, but they also make the definition of the comparison and the handling of repeated observations central to interpretation.
The primary outcome is a count of adenomas, while the study's stated aim refers to miss rates. These concepts are related but not interchangeable. A count describes the number identified under a defined assessment; a miss rate additionally depends on how missed lesions are identified and which lesions form the denominator. The registry record does not specify that operational definition. This illustrates why precise endpoint definitions are essential when a trial's title, rationale, and primary outcome use related but distinct terms.
The record also shows the difference between an outcome's stated purpose and an outcome result. A detailed rationale can explain why a device might alter visibility, but it cannot establish the size or certainty of an observed effect. Without numerical results and an analysis description, the statistical evidence cannot be appraised.
The record's planning framework is another useful distinction. Planning calculations based on an observed effect are illustrative; they do not retrospectively establish observed power or explain the original sample-size decision. The trial's own sample-size justification is not reported in the registry record. Keeping design assumptions separate from outcome evidence avoids treating a hypothetical planning exercise as a result.
Finally, the record's limited reporting of analysis populations, missing data, and safety denominators highlights how much information is needed to interpret a completed trial. The design label and enrollment count alone do not establish which participants contributed to the primary analysis or how uncertain the comparison is. These are general reporting principles that are especially relevant when outcomes are counts and observations may be repeated within participants.
13. 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 give numerical primary-outcome findings, despite listing the study as completed. It provides no adenoma counts by group, miss-rate estimate, treatment contrast, confidence interval, or p-value. This is the main limitation for interpreting the trial: the stated research question cannot be answered quantitatively from the posted record.
The endpoint description is not detailed enough to reproduce the intended analysis. It names the number of adenomas at the first colonoscopy and gives a timeframe after the second colonoscopy, while the study rationale emphasizes miss rates. The record does not define the lesion-level matching rules, denominator, or method for classifying a lesion as missed. It also does not report how the first and second examination findings were combined.
Key design and analysis details are absent. The record does not report the randomization procedure, exact crossover sequence, examination order details, handling of repeated observations, or statistical model. It does not state the analysis population, participant flow, missing-data methods, or whether all randomized participants completed both examinations. Baseline characteristics and eligibility criteria are also not reported, limiting assessment of the study population and generalizability.
The registry lists no masking, but does not identify who knew the assigned method or describe any independent review of adenoma findings. Adverse-event entries show zero at risk and zero affected in each group, and death values are null; these entries do not provide interpretable safety rates. The record does not explain those entries or provide additional safety information.
The trial is recorded as having 100 enrolled participants, but enrollment alone does not reveal the number analyzed for each outcome. The record also does not report the study's sample-size rationale, interim analyses, or a complete statistical analysis plan. These limitations concern what can be assessed from the registry record and should not be taken as proof that the underlying study lacked procedures or analyses that were not recorded there.
14. Related Tutorials
15. Related Statistical Calculators
16. Sources
- ClinicalTrials.gov: Cap-fitted Colonoscopy: a Randomized, Tandem Colonoscopy Study of Adenoma Miss Rates — NCT00577083.
- Registry record last updated 2018-12-10; status last verified 2017-03.
- Results first posted 2016-02-22.
- 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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17. Record Summary
The registry record describes NCT00577083, titled “Cap-fitted Colonoscopy: a Randomized, Tandem Colonoscopy Study of Adenoma Miss Rates.” It lists the study as completed, randomized, unmasked, and crossover, with 100 participants enrolled. The sponsor is Indiana University; the recorded start is 2006-11 and primary completion is 2009-10.
The intervention is cap-fitted colonoscopy, compared with regular colonoscopy without a cap. The primary outcome is titled Number of Adenomas, with the unit described as the first-colonoscopy number of adenomas after the second colonoscopy is completed. Examination time is listed as a secondary outcome.
The record does not report numerical primary-outcome results, a comparative effect estimate, or an analysis method. It also does not report participant flow, detailed endpoint definitions, missing-data handling, or the primary analysis population. The adverse-event entries do not provide interpretable incidence estimates. The registry therefore documents the study's aim and broad design, but not enough results to quantify or assess the primary comparison.