Educational CD-ROM Compared With Standard Informed Consent for Patients With Colorectal Cancer or a Family History of Colorectal Cancer: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Educational CD-ROM Compared With Standard Informed Consent for Patients With Colorectal Cancer or a Family History of Colorectal Cancer (NCT00450424), a randomized na study. The primary outcome is Impact of Standard Informed Consent vs CD-ROM Educational Intervention on Knowledge About Microsatellite Instability (MSI) Testing.

2. Clinical Question

The trial addressed a decision-support question rather than a clinical treatment outcome. MSI testing can involve information about inherited changes and family risk, so the study focused on participants’ understanding of the test. The posted primary result concerns the average survey score in each randomized condition. It does not directly measure whether participants ultimately chose testing, whether a choice was medically appropriate, or whether genetic or cancer outcomes changed.

3. Trial Design

This was a randomized, parallel-group clinical trial with no masking. Participants were assigned to a standard consent condition or a CD-ROM condition related to MSI testing. The registry record identifies Fox Chase Cancer Center as the sponsor, lists the trial as completed, and reports an enrollment of 239. The recorded start is 2007-06 and primary completion is 2011-11. The phase is listed as not applicable.

The intervention descriptions identify standard counseling and a CD-ROM intervention as the two counseling approaches. The record does not report an allocation ratio or explain how the random sequence was generated or concealed. Because masking is listed as none, the record does not indicate that participants or study staff were masked to the counseling condition. Further information about how the interventions were delivered, how much time participants spent with them, or whether delivery was standardized is not reported in the registry record.

The primary outcome was knowledge about MSI testing, assessed two weeks after enrollment using a 10-item true/false survey developed by the trial oncologists. The outcome is reported as a mean and standard deviation for each condition. The endpoint summaries list 106 participants for standard consent and 102 for the CD-ROM condition. These endpoint counts are distinct from the reported overall enrollment; the registry record does not explain the difference or describe the flow of participants from enrollment to endpoint assessment.

The record also lists three secondary outcome topics, covering decision satisfaction and difficulty, decisional conflict, attitudes and distress, family discussions, factors associated with the informed-consent process, and satisfaction with preparation to make a decision. Detailed numerical results for those secondary outcomes are not included in the posted information. A detailed protocol, original statistical analysis plan, and original sample-size justification are not reported in the registry 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

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 Impact of Standard Informed Consent vs CD-ROM Educational Intervention on Knowledge About Microsatellite Instability (MSI) Testing, measured over 2 weeks after enrollment.

The primary endpoint was knowledge about microsatellite instability (MSI) testing, measured with a 10-item true/false survey. The questions addressed details about MSI, including whether it occurs in every person who has had cancer and whether it may result from an inherited permanent gene change. The survey was developed by the trial oncologists. Scores could range from 0, when no questions were answered correctly, to 10, when all questions were answered correctly. The endpoint was assessed two weeks after enrollment.

Knowledge is relevant to informed decision-making because a person considering testing needs to understand what the test concerns. A survey score offers a quantitative summary of correct responses across the included questions. In this trial, the mean score describes average measured knowledge in each counseling condition; the standard deviation describes how much participant scores varied around that average. The survey measures responses to its specific items, not every aspect of understanding or decision quality.

As a general measurement point, a score can reflect only the content and format of its instrument. The registry record does not report evidence about the survey’s reliability or validation, nor does it report a threshold defining adequate knowledge. It also does not report whether the two-week assessment captured knowledge retention beyond that time. The primary endpoint should therefore be read as a short-term score on this study-specific knowledge survey, rather than as a comprehensive measure of informed choice.

7. Results Posted in the Registry

• CD-ROM Condition: mean 4.17 versus 4.07 on control; difference 0.10 (95% CI -0.61 to 0.81), standardized effect d = 0.04; z-test p = 0.784.

8. Statistical Interpretation

9. Statistical Methods Explained

The primary outcome is continuous: each participant’s survey score is a numeric quantity, and the registry reports a mean and standard deviation for each condition. A mean summarizes the average score within a group. A standard deviation describes the spread of individual scores around that group mean. These summaries are not interchangeable: similar means can occur alongside different amounts of variation, as the posted standard deviations illustrate.

What does the mean difference represent?

The reported mean difference compares the average score in the CD-ROM condition with the average score in the standard consent condition. Its estimate is 0.1 units. A positive value in this stated comparison direction means the CD-ROM group’s mean was higher; a negative value would mean it was lower. The estimate is measured in the survey’s score units, which run from 0 to 10. It is a difference between group averages, not a statement that every participant’s score changed by that amount.

In general, a group comparison estimates an average contrast between conditions. The estimate alone does not show how precisely that contrast has been measured. Uncertainty is expressed with a confidence interval and, under a statistical model, a p-value. The reported p-value is unadjusted, and the registry record does not describe an adjustment for other variables in the primary comparison. It does not report the full analysis procedure, such as the exact model or assumptions used to obtain the interval and p-value.

How should the p-value be understood?

In general, a p-value is calculated under a null hypothesis, commonly one that assumes no average difference between groups. It describes how often results at least as incompatible with that null model would arise if the model and its assumptions were true. It is not the probability that the observed difference occurred by chance, not the probability that either condition is superior, and not a measure of the magnitude of the difference. The posted unadjusted p-value is 0.784. That value should be read alongside the estimate and confidence interval rather than in isolation.

Why does the confidence interval matter?

In general, a confidence interval presents a range of effect values compatible with the data and the statistical method, at the chosen confidence level. Repeated use of the same method under its assumptions would produce intervals that cover the underlying value at the stated rate. A confidence interval does not assign a probability to the fixed effect being within one particular interval. In this trial, the reported interval crosses zero. That means it includes the possibility of no mean difference and also includes values on both sides of zero. The interval’s breadth is important: a result can have a high p-value and still leave meaningful uncertainty about the possible effect size.

Why can scores vary substantially?

Scores on a survey can differ between participants because of prior knowledge, experience, interpretation of questions, or other factors. These are general possibilities; the registry record does not identify which factors explain variation in this trial. Standard deviations of 2.25 and 2.94 describe the observed spread in the two conditions. Greater variation generally makes a group difference harder to estimate precisely when other aspects of a study are unchanged. The outcome’s bounded scale also means scores cannot fall below 0 or exceed 10.

The trial’s comparison is between randomized conditions, but the record lists no masking. Participants may have known whether they received standard consent or the CD-ROM. General methodological considerations include the possibility that awareness of assignment can affect responses or reporting; the record does not show whether this occurred. The registry also does not describe questionnaire administration, whether all participants received the survey in the same way, or whether data were checked for scoring errors.

The analysis is reported as a mean comparison. The registry record does not report a distributional assessment or a model that accounts for the bounded survey scale. As a general point, the mean can be a useful summary of a continuous score, while its interpretation depends on the measurement and on how the data are distributed. A standard deviation gives context about spread but does not reveal the full distribution, such as whether scores cluster at particular values or at the scale limits.

The outcome was measured two weeks after enrollment. That timing defines the scope of the primary result: it concerns knowledge at that assessment point. It does not establish persistence of knowledge at later times. The registry record does not report additional primary endpoint time points or a repeated-measures analysis. It also does not report an analysis population definition, such as whether all randomized participants were included regardless of attendance or survey completion.

Finally, statistical significance and practical relevance are distinct questions. In general, a small estimated difference may or may not matter to participants, depending on the context and an interpretable threshold. The registry record does not specify a minimum important difference for the knowledge survey. Without such a threshold, the practical meaning of a given score difference cannot be determined solely from its p-value. The posted estimate, interval, survey scale, and limitations of outcome reporting should be considered together.

10. Confidence Intervals and Precision

Precision concerns how narrowly the data and analysis constrain the effect estimate. The posted estimate is a mean difference of 0.1 units, and its confidence interval extends on both sides of zero. The interval therefore includes no difference and allows for estimates favoring either the CD-ROM condition or standard consent. Its endpoints are not repeated in numeric form; the essential interpretive point is that the interval is not confined to one side of zero.

In general, a confidence interval is influenced by the amount of information in the data and by variability in the outcome. The endpoint summaries report 106 participants in the standard consent group and 102 in the CD-ROM group, with standard deviations of 2.25 and 2.94, respectively. The scores vary considerably relative to the small observed difference. These features are consistent with uncertainty about the exact size and direction of the group contrast, but the registry record does not report a precision target for the trial.

The confidence interval should not be interpreted as a range containing a fixed proportion of individual participant scores. It describes uncertainty around a group-level effect under the analysis method. Nor does an interval that crosses zero prove that the groups are identical. It indicates that the posted data do not rule out zero difference at the interval’s confidence level, while also allowing values on either side. The record does not report a clinically or educationally meaningful threshold against which to judge those possible effects.

The reported p-value, 0.784, is consistent with the interval including zero, but neither statistic alone establishes equivalence. More precise evidence would require an interval narrow enough to distinguish the range of effects considered meaningful. No equivalence margin or precision-based design objective is reported in the registry record.

11. 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 estimates are participants per arm, not total participants and not total events. They are illustrative calculations based on the observed effect, not the trial’s original design assumptions. The stated assumptions are a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation; each planning scenario uses the stated fraction of the observed effect as the effect to detect. The trial’s own sample-size justification and original design assumptions are not reported in the registry record.

For 100% of the observed effect, the planning illustration gives 10,704 participants per arm for 80% power and 14,329 participants per arm for 90% power. For 75% of the observed effect, it gives 19,028 participants per arm for 80% power and 25,473 participants per arm for 90% power. For 50% of the observed effect, it gives 42,813 participants per arm for 80% power and 57,315 participants per arm for 90% power.

In general, power is the chance that a study designed under specified assumptions will detect an effect of a particular size according to its statistical decision rule. The 80% and 90% columns represent different planning targets under the stated assumptions; a higher target requires more participants for the same assumed effect. The illustrations also show that smaller effects need more participants to detect than larger effects. These are planning illustrations, not observed power. They are not a retrospective measure of whether the completed trial “had enough power,” and they do not replace the trial’s original design rationale.

12. 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 = 0.100; pooled standard deviation σ = 2.611.
2. n = 2 × (1.96 + 0.842)² × 2.611² / 0.100² = 10,703.2, rounded up to 10,704 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 <- 0.0999999999999996                      # observed difference in means
sigma <- 2.61118403005896                     # 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(450424)
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 = 10,704 (80% power), 14,329 (90% power)
 75% of observed effect: n per arm = 19,028 (80% power), 25,473 (90% power)
 50% of observed effect: n per arm = 42,813 (80% power), 57,315 (90% power)
power.t.test: 10704.1 
Simulated power at n = 10,704 per arm: 0.800 (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.

13. Multiplicity, Missing Data and Analysis Populations

The registry record lists three secondary outcome topics in addition to the primary knowledge outcome. These topics encompass satisfaction with and difficulty of the MSI testing decision, decisional conflict, attitude, general and cancer-related distress, discussions with family, factors associated with satisfaction and completeness of informed consent, and satisfaction with preparation to make a decision. The record does not provide numerical results for those secondary outcomes in the information.

When a study examines multiple outcomes or multiple comparisons, there is a general risk that some results may appear notable by chance. A prespecified analysis plan can explain which outcomes are primary, how secondary analyses will be interpreted, and whether adjustments for multiple testing are planned. The registry record does not report a multiplicity adjustment or a detailed plan for handling multiple comparisons. The p-value reported for the primary comparison is unadjusted. It should not be treated as evidence that all secondary questions were tested or that they support the same conclusion.

Missing data are also important because the primary endpoint summaries include 106 participants in the standard consent condition and 102 in the CD-ROM condition, whereas overall enrollment is 239. The registry record does not explain this difference, identify the number of participants with missing survey scores, or describe reasons for missingness. It does not report an imputation method, a sensitivity analysis, or how missing outcomes were handled. Without this information, it is not possible to assess from the registry record whether missingness could have affected the comparison.

The record does not define the analysis population for the primary outcome. It does not state whether the comparison included all randomized participants, only those who completed the survey, or another subset. Although the trial is described as randomized, the analysis population and participant flow are not reported. Baseline characteristics by condition and an adjusted primary analysis are also not reported in the information. These omissions do not establish that the analysis was biased, but they limit independent assessment of its conduct and robustness.

14. Safety Results

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

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 5% reporting threshold.

The safety record lists 117 participants at risk in the Standard Consent Condition and 122 in the CD-ROM Condition. It reports zero participants affected in the serious adverse event category and zero affected in the other adverse event category for both conditions. Death counts are not reported in the registry record.

These figures are counts of participants recorded as affected among the group-specific numbers at risk. They are not estimates of comparative risk, and no statistical comparison of adverse events is reported. The record does not provide event descriptions because no serious event terms are listed. It also does not describe the monitoring period, how adverse events were collected, or whether all events were actively solicited.

In general, a zero count in a registry entry means that no affected participants are recorded for that category in the posted data. It does not establish that an event is impossible or that no unrecorded event occurred. The trial’s principal focus was counseling and knowledge about MSI testing, and these safety figures should be interpreted as registry reporting rather than as a complete assessment of every possible harm.

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

The posted primary result is an average knowledge score of 4.07 under standard consent and 4.17 under the CD-ROM condition, with a mean difference of 0.1 units. The unadjusted p-value is 0.784, and the confidence interval includes values below and above zero. These data describe a small observed difference between the group means alongside substantial uncertainty about the underlying contrast.

The result does not establish that the two counseling approaches are equivalent. Equivalence would require a prespecified range of differences considered unimportant and an analysis demonstrating adequate precision within that range. The registry record does not report such a margin. The result also does not establish that the CD-ROM improves knowledge, or that it reduces knowledge; the interval allows effects in either direction.

The endpoint was a 10-item survey assessed two weeks after enrollment. It does not directly determine whether participants made an informed decision, chose MSI testing, understood every relevant aspect of testing, discussed risk with family, or experienced changes in distress. Those are separate questions, several of which appear among the registered secondary outcome topics, but detailed numerical results for them are not reported in the record.

Nor does the primary result answer whether knowledge persisted beyond the assessment time or whether results apply to people outside the trial’s intended population. The registry record does not provide detailed participant characteristics, the survey’s validation evidence, or information about later assessment. The endpoint should be interpreted as a short-term comparison on this particular survey, not as a broad measure of the overall quality of informed consent.

In general, an estimate and its uncertainty provide more information than a binary label of statistical significance. Here, the estimate is near zero, but the interval’s span means that the data do not pin down the true mean difference precisely. The registry record supports a cautious description of the posted knowledge scores, not a conclusion about clinical benefit, decision quality, or the value of either counseling approach for every patient.

16. Why This Trial Matters Statistically

This trial is statistically interesting because its primary question concerns how to measure an educational effect. The outcome is a bounded survey score, reported as a mean and standard deviation, and the comparison is between randomized counseling conditions. The posted group means are close, while the score distributions show substantial spread relative to the estimated difference. This makes precision and interpretation central: the point estimate alone gives an incomplete picture.

The confidence interval conveys that uncertainty includes no difference and values favoring either condition. That is more informative than treating the p-value as a verdict. A high p-value does not prove the interventions are identical, and a small estimated difference does not by itself determine whether the difference matters to participants. The registry record does not specify a threshold for a meaningful knowledge-score difference, so statistical and practical interpretation cannot be collapsed into one judgment.

The trial also illustrates the importance of reporting participant flow and analysis populations. Overall enrollment is 239, while the primary summaries list group-specific endpoint counts of 106 and 102. Without an explanation of the relationship between those counts, the reader cannot fully evaluate missing outcome data or determine precisely who contributed to the primary comparison. Clear reporting of follow-up and missing-data methods is important for understanding a randomized study’s results.

Finally, the study’s decision-support setting highlights the difference between a proximal outcome and a broader goal. Knowledge scores can inform understanding of one part of informed decision-making, but the score is not itself a complete measure of informed choice. The registry lists related secondary outcomes, yet their numerical results and the detailed analysis plan are not reported. This leaves the primary estimate useful but deliberately narrow in scope.

17. 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 offers limited detail for evaluating the trial beyond its design label and posted summaries. It does not report how randomization was generated or concealed, the allocation ratio, or the exact content and delivery procedures for the two counseling conditions. Masking is listed as none. The record does not describe whether participants completed the survey under comparable conditions or whether study staff had a role in outcome assessment.

The primary endpoint used a 10-item survey developed by the trial oncologists. The registry record does not report validation, reliability, or a threshold for adequate knowledge. The score is bounded from 0 to 10, but the posted result is summarized with means and standard deviations; the record does not describe the score distribution or any checks of model assumptions. Knowledge was assessed two weeks after enrollment, and longer-term retention is not reported.

There is an unexplained difference between the reported overall enrollment of 239 and the endpoint group counts of 106 and 102. The registry record does not provide participant flow, reasons for missing scores, missing-data methods, or an analysis-population definition. It also does not report baseline knowledge by condition, an adjusted primary analysis, or sensitivity analyses. The original sample-size justification and detailed statistical analysis plan are not reported.

Three secondary outcome topics are listed, but numerical secondary results are not included in the posted information. The record does not report how multiplicity was addressed or provide enough detail to assess all planned analyses. These reporting limitations restrict conclusions about the durability and breadth of any educational effect, as well as independent assessment of the robustness of the primary comparison.

18. Related Tutorials

19. Related Statistical Calculators

20. Sources

• ClinicalTrials.gov: Educational CD-ROM Compared With Standard Informed Consent for Patients With Colorectal Cancer or a Family History of Colorectal Cancer — NCT00450424.
• Registry record last updated 2014-09-05; status last verified 2014-09.
• Results first posted 2014-09-05.
• 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.

21. Record Summary

NCT00450424 is a completed randomized, parallel-group, unmasked trial sponsored by Fox Chase Cancer Center. It compared standard consent counseling with an educational CD-ROM intervention for MSI testing decisions among patients with colorectal cancer or a family history of colorectal cancer. The registry reports enrollment of 239, a start of 2007-06, and primary completion in 2011-11.

The primary outcome was knowledge about MSI testing, assessed two weeks after enrollment with a 10-item true/false survey. Mean scores were 4.07 for standard consent and 4.17 for the CD-ROM condition; the reported mean difference was 0.1, with an unadjusted p-value of 0.784. The confidence interval spans zero, leaving uncertainty about the direction and size of the difference.

The record lists three secondary outcome topics and reports zero participants affected in the serious and other adverse-event categories in both conditions. Detailed secondary results, participant flow, missing-data methods, the analysis population, and the trial’s original sample-size rationale are not reported in the registry record.