Dose the Saline Reduce the Mucus Production When Water Exchange Colonoscopy is Used?: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Dose the Saline Reduce the Mucus Production When Water Exchange Colonoscopy is Used? (NCT04769739), a randomized na study. The primary outcome is Left Colon Mucus Score.

2. Clinical Question

The study asks whether left-colon mucus scores differ among four colonoscopy approaches: traditional CO2 insufflation, water exchange with water, and water exchange with 50% or 25% saline. The primary outcome is a score describing the amount and appearance of residual mucus in the descending colon, sigmoid colon, and rectum, recorded during the colonoscopy procedure.

The registry description frames the study as a test of whether saline infusion changes mucus production during water-exchange colonoscopy. The four-arm structure matters to interpretation: comparisons with CO2 combine differences in colonoscopy approach and infused fluid, while the water-exchange water arm provides a reference for the saline arms within the water-exchange approach. The posted primary comparisons are each against CO2, rather than direct statistical comparisons between the saline and water-exchange water groups.

3. Trial Design

The registry identifies this as a randomized, double-masked, parallel-group trial. It was conducted at Evergreen General Hospital, Taiwan, and is marked completed. The recorded start date is 2021-08-04, and the primary completion date is 2022-03-23. Enrollment is listed as 301. The phase is recorded as not applicable.

Four groups are described. CO2 insufflation is the traditional approach, with minimal insufflation to aid insertion and cleaning performed during withdrawal. In the water-exchange water group, residual air is removed, water is infused to guide insertion through an airless lumen, and infused water and debris are removed predominantly during insertion. The two saline groups use the same general water-exchange approach, with either 50% saline, described as a 1:1 mixture of saline and water, or 25% saline, described as a 1:3 mixture.

Random assignment is stated in the registry, but the method used to generate the allocation sequence, conceal allocation, or implement masking is not reported in the registry record. The people who were masked are not specified in the registry record. The original sample-size justification, the planned allocation ratio, and details of the trial's statistical analysis plan are not reported in the registry record. The registry's enrollment figure and the arm counts attached to the posted primary outcome are different kinds of record entries; the record does not explain how they relate.

The primary outcome was assessed during the colonoscopy procedure, with a stated timeframe of 2 hours. Several secondary outcomes are listed, including adenoma detection rate, cecal intubation, bowel-preparation score, cecal intubation time, and withdrawal inspection time. Only some secondary outcomes have results posted. The record contains no reported analyses for the outcomes, so the posted group summaries and recalculated unadjusted comparisons should not be mistaken for a complete account of a prespecified analysis plan.

4. Participant Flow and Accounting

The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.

Overall Study

Reasons for not completing this period:

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 Left Colon Mucus Score, measured over 2 hours (data collected during colonoscopy procedure).

The primary endpoint is the left-colon mucus score, reported as a mean with a standard deviation. It measures visible residual mucus in the descending colon, sigmoid colon, and rectum. The registry defines a five-point scale running from score 0, no visible mucus, through score 4, more opaque mucus in thicker clumps covering more views of the lumen. Intermediate descriptions distinguish minimal clear streaks, mild opaque strands, and moderate opaque clumps covering one side of the surface.

The score is intended to turn a visual assessment of mucus into a structured outcome that can be compared across colonoscopy groups. A lower score corresponds to less mucus according to the scale's descriptions; a higher score corresponds to more visible or more extensive mucus. The group means therefore convey the average recorded score, while the standard deviations describe variation among participants within each group. They do not show the distribution of individual scores or the proportion of participants at each scale level.

Because the score has ordered categories and a fixed range, summarizing it with a mean treats the steps between adjacent scores as though they can be combined arithmetically. That is a common way to summarize a scale, but it can conceal whether differences arise from many small shifts or a smaller number of larger shifts. The registry does not report score distributions by category or the method used to assess mucus, so those details cannot be examined from the posted summary statistics.

7. Results Posted in the Registry

• WE With Water: mean 1.40 versus 0.20 on control; difference 1.20 (95% CI 0.99 to 1.41), standardized effect d = 1.82; z-test p = <0.001.
• WE With 50% Saline: mean 0.50 versus 0.20 on control; difference 0.30 (95% CI 0.16 to 0.44), standardized effect d = 0.67; z-test p = <0.001.
• WE With 25% Saline: mean 0.70 versus 0.20 on control; difference 0.50 (95% CI 0.33 to 0.67), standardized effect d = 0.95; z-test p = <0.001.

8. Secondary Efficacy Endpoints

The registry also posts results for secondary outcomes. For each outcome below, the endpoint type, the test applied to the posted summary statistics, the result and its interpretation are given in turn. Secondary endpoints are usually not adjusted for multiple testing, so they support rather than confirm the primary finding.

Adenoma Detection Rate

• Endpoint type: Binary: the number of participants with the event, compared as proportions.
• Test: Unadjusted two-proportion z-test, with a Wald 95% confidence interval for the risk difference.
• Result:
  • WE With Water: 41.3% (31/75) versus 50.0% (35/70) on control; risk difference -8.7 percentage points (95% CI -24.8 to 7.5), risk ratio 0.83 (0.58–1.18); unadjusted two-proportion z-test p = 0.295.
  • WE With 50% Saline: 53.9% (41/76) versus 50.0% (35/70) on control; risk difference 3.9 percentage points (95% CI -12.3 to 20.2), risk ratio 1.08 (0.79–1.48); unadjusted two-proportion z-test p = 0.633.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between WE With Water and the control. The interval gives the range of effects that remain compatible with the data.
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between WE With 50% Saline and the control. The interval gives the range of effects that remain compatible with the data.

Boston Bowel Preparation Scale Score

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard deviations.
• Result:
  • WE With Water: mean 7.10 versus 7.00 on control; difference 0.10 (95% CI -0.10 to 0.30), standardized effect d = 0.16; z-test p = 0.320.
  • WE With 50% Saline: mean 7.80 versus 7.00 on control; difference 0.80 (95% CI 0.60 to 1.00), standardized effect d = 1.31; z-test p = <0.001.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between WE With Water and the control. The interval gives the range of effects that remain compatible with the data.
  • The 95% confidence interval excludes no difference, so the mean is statistically higher for WE With 50% Saline than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.

Cecal Intubation Time

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard deviations.
• Result:
  • WE With Water: mean 18.00 versus 10.00 on control; difference 8.00 (95% CI 6.01 to 9.99), standardized effect d = 1.31; z-test p = <0.001.
  • WE With 50% Saline: mean 18.40 versus 10.00 on control; difference 8.40 (95% CI 6.27 to 10.53), standardized effect d = 1.27; z-test p = <0.001.
• Interpretation:
  • The 95% confidence interval excludes no difference, so the mean is statistically higher for WE With Water than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.
  • The 95% confidence interval excludes no difference, so the mean is statistically higher for WE With 50% Saline than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.

The posted secondary outcomes span detection, preparation quality, and procedural timing. The overall pattern is not uniform across those domains: the registry reports group summaries and some unadjusted comparisons for adenoma detection rate, bowel-preparation score, and cecal intubation time, while results for cecal intubation counts and withdrawal inspection time are not reported in the registry record.

These outcomes provide context but answer different questions from the primary mucus score. A preparation score describes bowel cleanliness; procedure times describe aspects of the examination; and adenoma detection is a participant-level finding. Any observed secondary pattern should therefore be interpreted on its own terms rather than as a direct confirmation of the mucus-score result. The registry does not report analyses linking individual mucus scores to these secondary outcomes.

The listed secondary comparisons are unadjusted. When multiple outcomes and group contrasts are considered, the chance of finding at least one apparently notable result can increase. The record does not state whether secondary outcomes were prespecified in a testing hierarchy, whether multiplicity was controlled, or whether the analyses were intended to be confirmatory. Their results consequently carry less inferential weight than a clearly specified primary analysis and should be treated as exploratory context.

The posted secondary results also do not include all outcomes named in the registry's secondary-outcome list. The absence of a posted result for an outcome is not evidence of no difference; it means the result is not reported in the registry record. Overall, the available secondary information neither replaces nor expands the primary endpoint beyond what the mucus score itself measures.

Secondary outcomes registered for this trial, for reference (only those above were recalculated):

• Adenoma Detection Rate
• Number of Participants With Cecal Intubation
• Boston Bowel Preparation Scale Score
• Cecal Intubation Time
• Withdrawal Inspection Time

9. Statistical Interpretation

10. Statistical Methods Explained

The primary outcome is continuous in the registry's statistical summary, and each arm is described by a mean and standard deviation. A mean is the arithmetic average of participant scores. The standard deviation describes how dispersed individual observations are around that average; it is not the uncertainty in the mean itself. The sample size and variation together influence how precisely a group mean can be estimated.

What does a mean difference represent?

Each posted primary comparison contrasts a water-exchange group with the CO2 group. The mean difference is the water-exchange group mean minus the CO2 group mean. A positive difference therefore indicates a higher average mucus score in the water-exchange group. For water exchange with water, the reported difference is 1.2; for 50% saline, it is 0.3; and for 25% saline, it is 0.5. These are unadjusted comparisons based on the posted summary statistics. They are not adjusted for other participant or procedural characteristics.

The comparison values also include pooled standard deviations and standardized mean differences. A pooled standard deviation combines the groups' variability into a common scale for describing the size of the mean contrast relative to within-group spread. A standardized difference can help compare contrasts measured on different scales, but it does not replace the raw mean difference in score units. The exact analysis model and test used by the trial team are not reported in the registry record.

How should a p-value be understood?

A p-value measures how incompatible the observed data are with a specified statistical null model, assuming that model and its assumptions apply. It is not the probability that the null hypothesis is true, nor does it measure the size or practical importance of a difference. The primary comparisons report p < 0.001. These are unadjusted p-values, and the record does not describe a multiplicity correction or a prespecified testing hierarchy. General statistical interpretation therefore calls for caution when several contrasts or outcomes are examined together.

What does the confidence interval add?

A confidence interval presents a range of values compatible with the observed estimate under the calculation's assumptions. For a mean difference, an interval that excludes zero indicates that the corresponding unadjusted comparison is inconsistent with a zero difference at the interval's nominal confidence level. The registry does not state the confidence level used for the recalculated intervals. The intervals convey uncertainty about the estimated contrast, but they do not account for every possible source of bias, such as outcome assessment or missing observations.

The primary score is ordered and bounded from 0 to 4. Treating it as a mean is a summary choice: it uses the numerical score values to calculate an average. As a general statistical consideration, a mean and standard deviation may not reveal the score distribution, especially if many observations lie near the lower bound or if scores cluster at particular categories. Category counts, medians, or an ordinal model could provide complementary descriptions, but the registry does not report those analyses.

Why can over-dispersion matter?

Over-dispersion is a general concern when a statistical model assumes less variability than the data contain. If the model understates variability, standard errors can be too small, confidence intervals too narrow, and p-values too optimistic. This trial's primary outcome is summarized as a bounded score, not as a count outcome in the posted results, so a count-model over-dispersion assumption is not established by the registry. More generally, analysts should match a model to the outcome's distribution and check whether its variability assumptions are reasonable. The registry record does not identify the model or diagnostics used for the trial's own analysis.

Randomization can support a causal comparison when allocation is implemented as intended and outcome data are handled appropriately. However, the registry does not report enough detail to evaluate sequence generation, concealment, masking implementation, adherence to assigned approaches, or the analysis population. The statistical summaries alone cannot establish whether all randomized participants were included in each analysis or how missing outcome data were handled.

The posted pairwise comparisons use CO2 as the reference for each water-exchange group. They do not provide a direct test comparing saline infusion with water infusion within the water-exchange approach. A contrast between two displayed group means is not itself a reported inferential test. Any such comparison would need its own estimate, uncertainty calculation, and consideration of the analysis plan; those are not reported in the registry record.

Finally, the registry reports no sponsor analyses for these outcomes. The comparisons accompanying the posted summaries are unadjusted recalculations, not evidence that the trial's investigators used the same method or reached the same analytic conclusions. The distinction matters because a trial's prespecified analysis may address stratification, covariate adjustment, missingness, or multiplicity in ways that a simple summary-statistic comparison does not.

11. Confidence Intervals and Precision

The primary mean-difference intervals are 0.990 to 1.41 for water exchange with water versus CO2, 0.157 to 0.443 for 50% saline versus CO2, and 0.332 to 0.668 for 25% saline versus CO2. Each interval lies above zero. In context, all three estimates indicate higher average mucus scores than the CO2 group, with the interval for each contrast giving a range of values compatible with the unadjusted calculation.

The intervals differ in width. The water-exchange water comparison spans a broader range than the two saline comparisons, while the saline intervals are more concentrated around their respective estimates. Interval width is affected by the observed variability and the number of participants in the groups being compared. A narrower interval indicates greater statistical precision for that contrast under the calculation; it does not by itself establish that the result is unbiased or clinically important.

The record does not report the confidence level or analytic method used to calculate these recalculated intervals. They should therefore be read as uncertainty summaries attached to the posted means and standard deviations, rather than as a substitute for a complete trial analysis. They also do not include uncertainty about how well the mucus score measures the underlying construct, whether scoring differed between assessors, or how missing data may have affected the results.

The standard deviations show that individual scores varied within groups: 0.38 for CO2, 0.84 for water exchange with water, 0.5 for 50% saline, and 0.63 for 25% saline. Standard deviations describe participant-level spread, whereas confidence intervals describe uncertainty about a group contrast. Keeping those ideas separate helps avoid reading a confidence interval as the range containing most individual scores.

12. Planning a Similar Trial: Sample Size

This is a planning illustration, not a re-evaluation of the original trial. It asks: if a new study wanted to detect a difference like the one observed, or a smaller one, how large would it need to be? It is deliberately not “observed power” of the finished trial, which is not a meaningful quantity.

The planning figures are illustrations based on the observed effect, not the trial's original design calculation. For these non-time-to-event outcomes, the displayed quantities are participants per arm, not total participants across groups or total events. The planning assumptions are a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. The effect to detect is the stated fraction of the observed effect.

The 80% power column gives the estimated participants per arm for a hypothetical study to have an 80% chance of detecting the specified effect under those assumptions, if the assumptions and effect size hold. The 90% power column expresses the corresponding planning target for a 90% chance. These figures are not observed power for this completed trial.

Rows that use a smaller fraction of the observed effect represent a more modest target difference. Detecting a smaller effect generally requires more participants because a subtle contrast is harder to distinguish from random variation. The planning values are sensitive to the observed effect and variability, so they should not be treated as a universal sample-size recommendation. The trial's own sample-size justification and original planning assumptions are not reported in the registry record.

13. How the Sample Size Is Derived

Power is the probability that a study of a given size rejects the null hypothesis when a specific true effect exists. It depends on four things: the effect to detect, the variability of the outcome, the significance level (here a two-sided α of 0.05, so z_1−α/2 = 1.960) and the desired power (z_1−β = 0.842 for 80% and 1.282 for 90%).

Formula

n is the number of participants in each arm, Δ is the difference in means to detect and σ is the common standard deviation.

Worked calculation for this trial

1. Observed difference Δ = 1.200; pooled standard deviation σ = 0.659.
2. n = 2 × (1.96 + 0.842)² × 0.659² / 1.200² = 4.7, rounded up to 5 participants per arm for 80% power.

The smaller-effect rows in the table above repeat the same calculation with the effect multiplied by 0.75 and 0.5 (for ratios, applied to the logarithm of the ratio).

R code

alpha <- 0.05
z_a   <- qnorm(1 - alpha / 2)          # two-sided
delta <- 1.2                      # observed difference in means
sigma <- 0.65940214498528                     # pooled standard deviation
n_per_arm <- function(power, frac = 1) {
  ceiling(round(2 * (z_a + qnorm(power))^2 * sigma^2 / (delta * frac)^2, 6))
}
for (f in c(1, 0.75, 0.5))
  cat(sprintf("%3.0f%% of observed effect: n per arm = %s (80%% power), %s (90%% power)\n", 100 * f,
              format(n_per_arm(0.80, f), big.mark = ","), format(n_per_arm(0.90, f), big.mark = ",")))

# Check against R's built-in function (t-based, so very slightly larger)
cat("power.t.test:", round(power.t.test(delta = delta, sd = sigma, power = 0.80)$n, 1), "\n")

# Simulation: exact two-sample t-test using simulated means and variances
set.seed(4769739)
n    <- n_per_arm(0.80)
reps <- 20000
m_diff <- rnorm(reps, delta, sigma * sqrt(2 / n))             # difference in sample means
s2     <- sigma^2 * rchisq(reps, 2 * (n - 1)) / (2 * (n - 1))   # pooled sample variance
tstat  <- m_diff / sqrt(s2 * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(tstat) > qt(0.975, 2 * (n - 1))), reps))

Output from running the code

100% of observed effect: n per arm = 5 (80% power), 7 (90% power)
 75% of observed effect: n per arm = 9 (80% power), 12 (90% power)
 50% of observed effect: n per arm = 19 (80% power), 26 (90% power)
power.t.test: 5.9 
Simulated power at n = 5 per arm: 0.707 (20000 replicates)

The simulation draws many sets of group means and variances at the planned sample size and counts how often the two-sample t-test rejects the null. It should land close to the target power; at very small required sample sizes it can fall below it, because the normal approximation is rough there.

14. Multiplicity, Missing Data and Analysis Populations

The registry lists a primary mucus-score outcome and several secondary outcomes, with multiple treatment groups and more than one possible pairwise contrast. The posted primary comparisons use CO2 as the reference, and the secondary results also include comparisons against that group. Testing multiple contrasts and outcomes raises a general multiplicity concern: without an analysis plan or adjustment strategy, nominal p-values do not necessarily represent the error rate for the full set of questions examined.

Multiplicity handling is not reported in the registry record. It is also not reported whether the investigators specified one primary contrast among the three comparisons with CO2, planned an overall test across all four groups, or used a sequential testing approach. The posted p-values are unadjusted, so they should be read as individual comparison results rather than as multiplicity-controlled evidence across every outcome and contrast.

Missing-data handling and the analysis population are not reported in the registry record. The posted arm counts for the primary outcome are 70, 75, 76, and 75. The record does not explain whether these counts represent all randomized participants, participants with an observed endpoint, or another analysis set. It does not describe exclusions, missing score values, imputation, or sensitivity analyses. Randomization is identified, but the registry does not say whether participants were analyzed according to their assigned groups.

These omissions limit assessment of potential bias. If outcome availability or analysis inclusion differed by group or participant characteristics, the observed summaries might not fully preserve the benefits of random assignment. No conclusion about the presence or extent of missingness can be drawn from the posted summaries alone.

The trial's statistical analysis plan, prespecified covariate adjustments, interim analyses, and stopping rules are not reported in the registry record. No sponsor-reported analyses are listed. As a result, the recalculated unadjusted summaries are useful for describing the posted data, but they cannot establish whether the original analysis followed a prespecified plan or how all planned analyses were handled.

15. Safety Results

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

Deaths

Other (non-serious) adverse events

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

The registry reports zero serious adverse events and zero other adverse events in each group. The numbers at risk for both adverse-event categories are 70 in the CO2 group, 75 in the water-exchange water group, 76 in the 50% saline group, and 75 in the 25% saline group. Deaths are recorded as zero in every group.

These figures describe what was recorded for the listed groups in the registry. They should not be read as proof that no adverse event could occur or that the approaches have equivalent safety. The record does not provide event definitions, collection procedures, follow-up details, or an explanation of whether every enrolled participant was included in the safety assessment. With no recorded events, the posted counts also cannot describe the types or severity of events that might be uncommon.

Serious and other adverse events are separate reporting categories. The zero counts in both categories are reassuring as a description of the registry entry, but they do not establish absence of risk or support a comparative safety conclusion. Safety interpretation is limited by the size of the groups, the reporting detail, and the lack of a stated safety-analysis method.

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

The posted primary results show higher average mucus scores in each water-exchange group than in the CO2 group. The largest reported difference from CO2 is for water exchange using water; the two saline-group differences are smaller. The confidence intervals for the three unadjusted contrasts all lie above zero, and each comparison has p < 0.001. This is a description of the observed score summaries and their statistical uncertainty.

The pattern does not establish a direct saline-versus-water effect. Each reported primary contrast is against CO2, and CO2 differs from water exchange in procedural approach as well as in the fluid used. The study has a water-exchange water group, but no direct inferential saline-versus-water comparison is reported. The displayed group means alone do not test whether either saline concentration differs from water within the water-exchange method.

The outcome is a visual score of mucus, not a measure of patient symptoms, a complication, or a longer-term clinical outcome. The registry does not report whether a particular score difference is clinically meaningful or how mucus scores relate to outcomes important to patients. A statistically distinguishable average score is not by itself evidence of a clinical benefit, and the posted results should not be interpreted as advice about which colonoscopy approach to use.

The five-point score is bounded and ordered, while the posted summaries use means and standard deviations. Without score-category distributions, readers cannot see how many participants had no visible mucus, how observations were distributed across intermediate categories, or whether a small group of higher scores influenced the means. The registry also does not report the scoring procedure or reliability information.

Finally, the record leaves important analytic details unreported, including missing-data handling, analysis populations, multiplicity, and the trial's original statistical plan. These limits do not erase the observed differences, but they constrain how far those differences can be generalized or interpreted. The most defensible reading is that the posted unadjusted summaries show different average mucus scores across the recorded groups, while questions about direct saline effects, clinical importance, and broader applicability remain unresolved by the registry record.

17. Why This Trial Matters Statistically

This trial illustrates why the comparator and the structure of a multi-arm design matter. The CO2 group is a reference for each posted primary contrast, but it is not the same procedural approach as water exchange. A contrast between saline water exchange and CO2 therefore combines several features of the assigned approach. The water-exchange water arm is important for contextualizing the saline arms, yet direct inferential comparisons with that arm are not reported.

It also illustrates the difference between an outcome's clinical description and its statistical summary. Mucus is assessed on an ordered, bounded scale, while results are reported as means and standard deviations. That summary is straightforward to compare, but category-level information would help readers understand what participant score patterns produced the averages.

The posted results make uncertainty visible through confidence intervals rather than relying only on p-values. The intervals show the range of unadjusted mean differences compatible with the calculations, while the p-values address compatibility with a zero-difference model. Neither provides a measure of clinical importance, and neither addresses unreported design and analysis details.

Finally, this record highlights the importance of complete reporting. Multiplicity strategy, missing-data methods, analysis populations, and the original sample-size rationale are not reported. Those details determine how confidently readers can connect randomized assignment, observed outcomes, and the trial's intended statistical claims. The study is therefore useful for examining how descriptive results and unadjusted contrasts should be interpreted without treating them as a complete analysis plan.

18. 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 does not report the method of random sequence generation, allocation concealment, or which individuals were masked. Those omissions make it difficult to assess implementation of the randomized, double-masked design from the record alone. The mucus outcome is a visual assessment, but assessor training, reliability, and procedures for resolving disagreement are not reported.

The primary score has five ordered categories and a fixed range, yet only means and standard deviations are posted. Category-specific counts and individual-level distributions are not reported. That limits assessment of floor effects, skew, and whether the group averages represent broadly similar shifts across participants. A clinically meaningful difference for the score is also not reported.

The primary comparisons are against CO2, not direct saline-versus-water comparisons within water exchange. Since the treatment groups differ in procedural approach and fluid, the CO2 contrasts do not isolate the effect of saline concentration. The record does not report an overall four-group test or a prespecified set of pairwise comparisons.

Missing-data methods and analysis populations are not reported, and the relationship between the enrollment figure of 301 and the primary outcome arm counts is not explained. Multiplicity handling and the trial's own sample-size justification are also not reported. The posted secondary results cover only some outcomes named in the registry. These specific reporting gaps restrict interpretation of the posted estimates and limit assessment of whether the displayed comparisons represent the complete set of planned analyses.

19. Related Tutorials

20. Related Statistical Calculators

21. Sources

• ClinicalTrials.gov: Dose the Saline Reduce the Mucus Production When Water Exchange Colonoscopy is Used? — NCT04769739.
• Registry record last updated 2024-01-05; status last verified 2023-04.
• Results first posted 2024-01-05.
• 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.

22. Record Summary

NCT04769739 is a completed, randomized, double-masked, parallel trial sponsored by Evergreen General Hospital, Taiwan. The registry records enrollment of 301, a start date of 2021-08-04, and primary completion on 2022-03-23. The study compares CO2 insufflation with water-exchange colonoscopy using water, 50% saline, or 25% saline.

The primary outcome is the left-colon mucus score, a five-point visual scale summarized by group means and standard deviations. The posted unadjusted comparisons against CO2 show higher mean scores in all three water-exchange groups, with confidence intervals above zero and p < 0.001 for each comparison. Selected secondary outcomes and zero adverse-event counts are also posted.

The registry does not report the trial's full statistical plan, multiplicity strategy, missing-data approach, analysis populations, or direct saline-versus-water comparisons. The displayed results support description of the posted group summaries, with those reporting limits kept in view.