Community Interventions in Non-medical Settings to Increase Informed Decision Making for Prostate Cancer Screening: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Community Interventions in Non-medical Settings to Increase Informed Decision Making for Prostate Cancer Screening (NCT00207636), a randomized na study. The primary outcome is Percentage of Patients Who Were Ready to Make a Decision or Were Undecided.

2. Clinical Question

The study concerned decision making about PSA screening, rather than a comparison of screening itself or prostate cancer outcomes. The stated purpose was to develop and evaluate an educational, interactive decision aid for men considering the test. The registry summary says that major medical organizations recommend discussion of screening risks and benefits with a physician before making a decision; the aid was intended to help prepare participants for that discussion.

The primary outcome is described by the percentage of participants who were ready to make a decision or were undecided. The registry definition also distinguishes participants classified as decided from those classified as undecided. The scale offered five response options, ranging from not having thought about the decision to having made a decision unlikely to change. Because the registry record does not report an analyzed comparison, it does not establish how these response categories differed between the study arms or over time.

3. Trial Design

This was a completed, randomized, parallel-group study of community interventions in non-medical settings to increase informed decision making about prostate cancer screening. The registry lists an enrollment of 812 and identifies the condition as prostate cancer. The study began in 2004-12, and primary completion was recorded as 2009-08. The sponsor was the Centers for Disease Control and Prevention.

Participants were assigned to a control arm, which received printed materials, or to an experimental arm with access to the Computer Assisted Decision making tool. The registry describes the latter as a computer-tailored decision aid designed to promote informed decision making. The trial is listed as unmasked. The model is parallel, so the registry describes separate arms rather than a crossover design.

The intervention was behavioral, and the phase is listed as not applicable. The brief summary frames the aid as a way to help men prepare for a physician discussion about the risks and benefits of PSA screening. The primary outcome was assessed at baseline and follow-up, up to 10 months. The registry also lists secondary outcomes concerning decision-making style and decisional conflict.

The registry record does not report the allocation ratio, detailed randomization procedures, intervention delivery procedures, or a protocol-based sample-size justification. It also does not report an analysis population or a statistical analysis plan. Although the study status is completed, no analyses are listed in the record. Consequently, the design and planned outcome concepts can be described, but the posted record does not support a conclusion about the observed effect of the decision aid.

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 Percentage of Patients Who Were Ready to Make a Decision or Were Undecided, measured over Assessed at baseline and follow-up, up to 10 months.

The primary endpoint is titled “Percentage of Patients Who Were Ready to Make a Decision or Were Undecided.” It measures decision readiness using the Stage of Decision-Making Scale, described in the registry as having five responses. The scale ranges from not having thought about the decision to having made a decision that is unlikely to change. The registry definition classifies as decided participants who had made a decision either while remaining willing to reconsider or while being unlikely to change their minds. Participants who had not thought about the decision or were uncertain were classified as undecided.

This kind of outcome is relevant to a decision aid because the intervention’s stated aim is to support informed decision making and preparation for a discussion with a physician. In general, a decision-readiness measure describes participants’ reported position in a decision process; it is not, by itself, a measure of screening uptake, diagnostic accuracy, cancer outcomes, or whether a decision was medically preferable. Interpretation also depends on how the categories are combined and compared across arms and assessment times.

The registry states that assessment occurred at baseline and follow-up, up to 10 months. It does not provide a single analyzed endpoint comparison or report the results for any response category. The primary outcome is therefore described, but its observed value and between-arm pattern are not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The design is listed as randomized and parallel. In general, random assignment is intended to make study groups comparable, on average, with respect to measured and unmeasured characteristics at the start of a trial. It does not guarantee identical groups in a particular study. A parallel design assigns participants to separate study arms and follows those arms under their assigned conditions. Here, the registry describes a computer-assisted decision aid and distribution of printed materials as the two approaches. The record does not report the allocation ratio or the operational details of randomization.

What an outcome comparison would need to specify

The primary outcome is expressed as a percentage and refers to participants’ decision readiness. In general, a percentage comparison requires a clear numerator, denominator, and definition of the event or category being counted. This is especially important when the underlying outcome has several response categories. A comparison might retain categories separately or define a combined outcome, but those choices answer different questions. The registry record does not report a single analyzed comparison for the primary endpoint, and the category-level results are not reported in the registry record.

Assessment is described at baseline and follow-up up to 10 months. In general, repeated measurements can be analyzed by comparing follow-up values, by adjusting follow-up for baseline, or by modeling measurements across time. These approaches have different interpretations and assumptions. A repeated-measures analysis must account for the fact that observations from the same participant are related; treating them as independent can misrepresent uncertainty. The registry record does not report which approach, if any, was used.

Estimates and uncertainty

In general, an effect estimate should be accompanied by a measure of uncertainty. A confidence interval communicates how much precision the data and analysis provide for the estimated contrast. A narrow interval indicates greater precision than a wide interval, while the interval’s location indicates which effects remain compatible with the analysis. A confidence interval is not a guarantee that the true effect lies inside it, and it does not replace clinical or scientific judgment. No confidence interval or effect estimate for the primary comparison is reported in the registry record.

In general, a hypothesis test evaluates data against a specified null model. A p-value is not the probability that the null hypothesis is true, nor does it measure the size or practical importance of an effect. Its interpretation depends on the analysis and assumptions used. The registry record reports no primary-outcome test statistic or p-value. The planning illustration specifies a two-sided significance level of 0.05, but that planning assumption is not a reported trial result.

Planning calculations

The registry’s sample-size assumptions describe an illustration based on the observed effect, equal allocation between arms, a normal approximation, and a two-sided significance level of 0.05. The stated effect to detect is a fraction of the observed effect. Such calculations can illustrate the number of participants per arm associated with a chosen target for power under specified assumptions. They do not tell readers how many participants actually experienced an outcome, and they are not observed power. The record does not report the protocol’s sample-size justification or give the numerical outputs of the planning illustration.

In general, a planning calculation is sensitive to the assumed effect, outcome variability, allocation, significance level, and chosen power target. If an assumed effect is optimistic, the resulting planning estimate may not reflect the requirements for detecting a smaller effect. A calculation based on an observed effect is particularly important to distinguish from a prospective design justification: it describes a hypothetical planning scenario rather than showing that the trial was designed with that assumption. The registry does not report the observed effect used in the illustration, so its numerical implications cannot be assessed from this record.

Category structure and over-dispersion

The primary measure involves categories of decision readiness. In general, a multi-category outcome contains more information than a simple yes-or-no classification, but it may require a model that respects the ordering or distinct meaning of categories. Combining categories can simplify interpretation while discarding distinctions. The analysis note says the outcome has several categories or time points and was not reduced to one comparison, so a single binary effect should not be inferred.

Over-dispersion is a general concern when observed variation is greater than a statistical model expects. If a model assumes less variation than the data contain, standard errors may be too small and confidence intervals may be too narrow. The registry record does not identify a fitted model, report a dispersion assessment, or provide evidence that over-dispersion was relevant to this trial’s analyses. It should therefore be treated as a general methodological consideration, not as a documented feature of the posted results.

What is documented

The record identifies the trial as randomized, unmasked, and parallel, and describes the intervention and comparator. It also identifies the outcome concepts and assessment period. It does not report an analysis method, adjustment variables, handling of repeated observations, missing-data method, or analysis population. These details are needed to judge whether an estimate is robust to modeling choices and whether its uncertainty is appropriately represented. With no analyses listed, the registry record supports explanation of the statistical questions but not reconstruction of an analysis or independent verification of a result.

10. Multiplicity, Missing Data and Analysis Populations

The primary outcome description includes multiple decision-readiness categories and assessment at baseline and follow-up up to 10 months. The registry analysis note indicates that the outcome has several categories or time points and was not reduced to one comparison. The record does not report which categories or time points were designated as primary for inference, nor does it describe any multiplicity strategy. It is therefore not possible to determine how the study addressed the risk of false-positive findings from examining multiple outcomes, categories, or times.

The registry lists secondary outcomes concerning decision-making styles and decisional conflict, as well as six outcome measures overall. It does not report a hierarchy of outcomes, a prespecified testing sequence, or an adjustment for multiple comparisons. These details are not reported in the registry record. In general, examining many outcomes can increase the chance that at least one result appears statistically unusual by chance; an analysis plan can clarify which comparisons are confirmatory and how other findings should be interpreted. No such plan is described in the posted record.

The registry does not report missing-data counts, reasons for missingness, imputation procedures, or sensitivity analyses. It also does not identify whether the analysis included all randomized participants or another analysis population. These omissions matter because incomplete follow-up can affect both the estimated outcome and its uncertainty, particularly when missingness differs between arms or relates to decision readiness. No conclusion about the extent or consequences of missing data can be drawn.

The record lists no analyses, so it does not show whether participants were analyzed according to randomized assignment, whether adherence was considered, or how baseline and follow-up responses were handled. Those analysis-population and missing-data details are not reported in the registry record.

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

The record establishes that a completed randomized study compared access to a computer-tailored decision aid with distribution of printed materials. Its stated purpose was to support informed decision making about PSA screening and help men prepare for discussion with a physician. The primary outcome was decision readiness, assessed at baseline and follow-up up to 10 months. These details clarify the question the study was designed to address.

The registry record does not report an analyzed primary outcome or a numerical comparison between arms. It therefore cannot show whether decision readiness differed, how large any difference may have been, or how precisely it was estimated. The absence of an analysis is not evidence that the interventions were equivalent, that they had no effect, or that one approach was better. Those interpretations require results and an analysis that are not reported in the registry record.

Even if a difference in decision-readiness categories were available, it would describe that measured decision process rather than establish effects on screening behavior, prostate cancer diagnosis, or health outcomes. The registry’s stated aim is educational and decision-focused. In general, a measure of readiness can characterize where participants report being in a decision, but it does not establish whether a decision is informed, stable, or consistent with an individual’s preferences unless those aspects are measured and analyzed.

The planning assumptions are not outcome evidence. A sample-size illustration based on an observed effect does not demonstrate that the study had adequate power, and it is not observed power. The record does not give the numerical planning outputs or the effect estimate used to generate them. Likewise, the zero entries in adverse-event fields occur alongside zero numbers at risk and cannot be interpreted as evidence of no events among enrolled participants.

The appropriate interpretation is therefore descriptive and limited to the registry’s documented design and outcomes. The posted record does not provide the statistical results needed to assess the decision aid’s effect or the precision of that effect.

12. Why This Trial Matters Statistically

This trial addresses a statistical question about a behavioral intervention: whether access to an interactive decision aid is associated with different reported decision readiness than distribution of printed materials. That question differs from asking whether PSA screening changes a health outcome. Keeping the measured endpoint distinct from broader clinical outcomes is essential when interpreting behavioral and decision-support research.

The registry description also illustrates why outcome definition matters. Decision readiness is recorded through a scale with several responses, and the primary outcome refers to participants who were ready to decide or undecided. The way response categories are grouped, and the way baseline and follow-up measurements are compared, can change the interpretation. The record does not report a single analyzed comparison, so the statistical contrast cannot be inferred from the endpoint title alone.

Randomized allocation can support a fair comparison when the analysis follows the design and accounts for the outcome structure and missing data. But a design description is not a substitute for reported estimates. Readers need results, uncertainty, and analysis details to judge the magnitude and precision of a contrast. Here, the registry lists no analyses, which limits statistical interpretation despite the clearly described intervention and comparator.

The record further distinguishes trial results from planning illustrations. Planning calculations rely on assumptions and do not show what happened among participants. This distinction is important when considering any sample-size output based on an observed effect: it is a planning scenario, not a measure of achieved power or proof of an effect.

For biostatisticians and clinical researchers, the main lesson is that an interpretable trial record needs more than a randomized design and a stated endpoint. Category definitions, time-point handling, analysis populations, missing-data methods, and estimates with uncertainty are all needed to evaluate the evidence. Those elements are not reported in the registry record for this study.

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 main limitation for interpreting this trial is that the registry record lists no analyses. Although the study is marked completed and reports enrollment of 812, it does not provide a primary-outcome estimate, category counts, uncertainty interval, or statistical test. The direction, magnitude, and precision of any between-arm difference cannot be assessed from the posted record.

The primary endpoint has several response categories and is assessed at baseline and follow-up up to 10 months. The registry analysis note states that it was not reduced to one comparison. No detailed outcome-coding rule for a reported contrast, model, or approach to repeated measurements is described. This leaves uncertainty about how the stated endpoint would translate into an analyzed effect.

The record does not report participant eligibility details in the primary outcome description, the allocation ratio, detailed randomization procedures, or the statistical analysis plan. It also does not identify the analysis population or describe missing observations, attrition, adherence, or sensitivity analyses. These omissions limit assessment of selection, follow-up, and analysis-related uncertainty. The record’s completion status alone does not resolve these issues.

Six outcome measures are listed, including secondary measures of decision-making style and decisional conflict, but no outcome results are reported. The record does not describe multiplicity handling or identify how confirmatory and exploratory outcomes were distinguished. The adverse-event entries list zero numbers at risk as well as zero event counts, so they do not permit a meaningful safety comparison.

These are limitations of the information available in the registry record. They do not establish that the trial itself lacked an analysis plan or that results were not analyzed elsewhere; those details are simply not reported in the registry record.

14. Related Tutorials

15. Related Statistical Calculators

16. Sources

• ClinicalTrials.gov: Community Interventions in Non-medical Settings to Increase Informed Decision Making for Prostate Cancer Screening — NCT00207636.
• Registry record last updated 2025-01-14; status last verified 2024-12.
• Results first posted 2025-01-14.
• 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.

17. Record Summary

NCT00207636 is a completed randomized, parallel, unmasked trial of a computer-assisted decision aid for men considering PSA screening for prostate cancer. The comparison was access to the computer-tailored aid versus distribution of printed materials. The registry lists enrollment of 812, a study start of 2004-12, and primary completion in 2009-08. The sponsor was the Centers for Disease Control and Prevention.

The primary outcome concerned the percentage of participants ready to make a decision or undecided, assessed at baseline and follow-up up to 10 months. Secondary outcomes concerned decision-making styles and decisional conflict. The registry lists six outcome measures but no analyses. It does not report a primary-outcome effect estimate, uncertainty interval, or p-value, so the statistical effect of the intervention cannot be evaluated from the posted record.