Shared Decision Making in Rural Primary Care Lung Cancer Screening and Smoking Cessation: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Shared Decision Making in Rural Primary Care Lung Cancer Screening and Smoking Cessation (NCT04897568), a randomized na study. The primary outcome is Count of Participants Who's Health Visit Adhered to the LCS Guidelines and CMS Coverage Criteria in Rural Primary Care Practices: Baseline Survey.

2. Clinical Question

The central statistical issue is that the posted primary result is labeled as a baseline measure, while the study description also identifies a later intervention phase. The registry record does not report an intervention-versus-control estimate for change over time on this primary measure. Consequently, the posted baseline counts describe the recorded result but do not by themselves answer whether the decision aid changed adherence. The posted knowledge outcome is also measured at baseline, so it should not be read as a treatment effect.

3. Trial Design

NCT04897568, titled “Shared Decision Making in Rural Primary Care Lung Cancer Screening and Smoking Cessation,” is listed as a randomized, unmasked crossover study sponsored by the University of Colorado, Denver. Its phase is listed as NA. The registry records enrollment of 120 and status as completed. The recorded start date is 2020-07-15, and the primary completion date is 2023-04-30.

The study description frames the intervention as a way to support adherence to lung cancer screening guidelines and Centers for Medicare and Medicaid Services coverage criteria, conduct shared decision-making, and provide smoking cessation services in rural primary care practices. The intervention is listed as a patient decision aid. The control description refers to each participant and clinic before the intervention, at baseline during the first 2 months. The intervention description refers to each participant and clinic after moving to the intervention phase, following the first 2 months.

In a crossover design, participants or settings experience more than one study condition or period, so comparisons may depend on both condition and timing. That general feature makes it important to know how sequence, period, and within-participant dependence were handled. Those details, including the allocation sequence and the statistical treatment of repeated observations, are not reported in the registry record. The record states that allocation was randomized and masking was none; it does not describe additional masking procedures.

The posted primary result lists 64.0 in the control arm and 54.0 in the patient decision aid arm. These are the arm-level counts attached to that result, not a complete account of participant flow. The registry does not report why the arm counts differ from the enrollment entry, whether all randomized participants contributed data, or how missing observations were handled. No analysis population definition or analysis results beyond the posted summaries are 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.

Population: Patients

6. Primary Endpoint

The registry lists the primary outcome as Count of Participants Who's Health Visit Adhered to the LCS Guidelines and CMS Coverage Criteria in Rural Primary Care Practices: Baseline Survey, measured over Baseline.

The primary endpoint is a count of participants whose health visit adhered to lung cancer screening guidelines and Centers for Medicare and Medicaid Services coverage criteria in rural primary care practices. The registry describes adherence as a latent concept measured through a composite based on a baseline survey administered immediately after a healthcare provider visit. The survey counts “Yes” responses to three questions: whether the participant was given a decision aid during the last clinic visit or call; whether the provider or staff reviewed the aid with the participant; and whether the provider recommended a low-dose CAT scan.

A composite can capture several related actions that together represent a broader care process. Counting positive responses offers a way to operationalize whether specific elements of shared decision-making and screening-related care occurred. It also means the measure is not a direct assessment of every aspect of clinical guideline adherence: its interpretation is tied to the questions included in the survey. The registry does not report the survey’s validation, scoring rules beyond counting “Yes” responses, or how incomplete answers were treated.

The baseline timing matters for interpretation. A baseline measure can describe the starting state, but a baseline-only comparison does not establish what changed after an intervention. Although the study description includes a later patient decision aid phase, the primary result is titled as a baseline survey result. A post-intervention estimate or a change-from-baseline analysis for this endpoint is not reported in the registry record. The posted primary result therefore should be understood as the baseline count summary, not as evidence of an intervention effect.

7. Results Posted in the Registry

• Patient Decision Aid: 0.0% (0/54) versus 0.0% (0/64) on control; risk difference 0.0 percentage points (95% CI 0.0 to 0.0); unadjusted two-proportion z-test p = n/a.

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.

Patient Knowledge About Lung Cancer

• 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:
  • Patient Decision Aid: mean 8.50 versus 8.10 on control; difference 0.40 (95% CI -0.29 to 1.09), standardized effect d = 0.20; z-test p = 0.257.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Patient Decision Aid and the control. The interval gives the range of effects that remain compatible with the data.

The registry lists Patient Knowledge About Lung Cancer as a secondary outcome, and the posted result is a baseline score. Its group means and unadjusted comparison are descriptive of the baseline data. They do not provide evidence of a post-intervention change, and they should not be combined with the primary baseline adherence result to imply that the intervention affected either outcome.

The knowledge outcome and the primary outcome address different aspects of care. One concerns a score about lung cancer knowledge; the other is intended to represent visit adherence through several survey responses. In general, a knowledge score may provide context about what participants know, while a process measure may capture actions taken during a visit. A pattern across these outcomes could be informative if each were measured at comparable times and analyzed in a way that reflects the study design. The registry’s posted results do not include an intervention-period comparison for either outcome, so such a pattern cannot be established from the record.

The secondary listing repeats the same named knowledge outcome. The registry does not explain whether the repeated listing reflects separate measures, time points, or a record-entry duplication. The posted secondary summary is therefore best read as the stated baseline knowledge result without assigning it an unreported interpretation.

Unadjusted secondary findings carry less weight than prespecified, appropriately analyzed primary comparisons because multiple outcomes or comparisons can increase the chance of a nominally unusual result. Adjustment, hierarchy, and confirmatory status can help clarify how much emphasis to place on secondary findings. Those decisions are not reported in the registry record, and the registry lists no reported analyses. The unadjusted p-value should consequently be treated as a descriptive statistical summary, not as a stand-alone confirmation of an intervention effect.

More broadly, the secondary result cannot resolve the ambiguity in the primary baseline result. A baseline difference in knowledge, even if precisely estimated, would not show that the decision aid changed knowledge. A post-intervention estimate and a comparison that respects the crossover design would be needed to address that question; such results are not reported in the registry record.

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

• Patient Knowledge About Lung Cancer
• Patient Knowledge About Lung Cancer

9. Statistical Interpretation

10. Statistical Methods Explained

Randomization is intended to reduce systematic differences between assigned conditions, but it does not by itself determine how all trial data should be analyzed. In a crossover study, timing and repeated observations matter because the same participant or clinic may contribute information under more than one condition. General statistical practice would consider whether observations are paired or otherwise correlated, whether period effects are plausible, and whether the assigned sequence is relevant. The registry record identifies randomization and a crossover model but does not report the analysis method used to address these features.

What does a risk difference represent?

For a binary outcome, a risk difference compares the proportion meeting the outcome in one group with the proportion in another. It is expressed on the same scale as the proportions, rather than as a ratio. Here the posted primary result gives a risk difference of 0.0 and interval limits of 0.0 and 0.0. The registry also gives zero values for the two arm results. The meaning of those values depends on the endpoint scoring and denominator definitions, which are not described beyond the survey composite and arm counts. The reported estimate should therefore be quoted as entered rather than expanded into an unreported interpretation of how the survey responses were classified.

What does a mean difference represent?

For a continuous outcome, a mean difference is the mean in one group minus the mean in the comparison group, with the direction depending on the stated comparison. The knowledge outcome is reported as a score on a scale, with means of 8.1 and 8.5, and a mean difference of 0.4. A mean difference is a difference in average scores; it does not describe every participant’s score or the spread of individual responses. The standard deviations, 2.3 and 1.5, provide information about variability within each group.

How should the confidence interval be read?

A confidence interval expresses uncertainty around an estimate under the statistical method used. In general, a wider interval indicates less precision, while a narrower interval indicates greater precision, although the interpretation also depends on the scale and design. The knowledge outcome’s interval spans values below and above zero. Thus the reported data do not narrowly locate the difference on one side of zero. The registry does not report the method used to construct this interval or whether it accounts for the crossover structure or clustering within clinics.

What does an unadjusted p-value tell the reader?

A p-value measures how unusual data at least as discrepant as those observed would be under a specified null model and its assumptions. It is not the probability that the null hypothesis is true, nor does it measure the size or practical importance of an effect. The posted unadjusted p-value for the baseline knowledge comparison is 0.257. Because it is unadjusted, it does not account for the possibility of examining multiple outcomes or comparisons. The registry does not report a multiplicity strategy, and no reported analyses are listed.

Why does over-dispersion matter?

General statistical methods for counts often assume a particular relationship between the mean and variability. Over-dispersion occurs when the observed variability is greater than a model assumes. If it is ignored, standard errors can be too small and intervals or tests can appear more precise than warranted. This trial’s posted primary endpoint is a count-based composite, but the registry does not report a count model, an over-dispersion assessment, or a model-based analysis. The concern is therefore a general methodological consideration, not a claim that over-dispersion occurred in this study.

How should planning illustrations be interpreted?

The planning illustrations are calculations based on the observed knowledge effect, using a two-sided significance level of 0.05, equal allocation, and a normal approximation. They are not observed trial results, do not establish the study’s original design assumptions, and are not observed power. The registry identifies the effect to detect as a stated fraction of the observed effect. For planning for 100% of the observed effect, the illustration gives 383 participants per arm for 80% power and 513 participants per arm for 90% power. For planning for 75% of the observed effect, it gives 681 participants per arm for 80% power and 911 participants per arm for 90% power. For planning for 50% of the observed effect, it gives 1,531 participants per arm for 80% power and 2,050 participants per arm for 90% power.

These illustrations are conditional on their stated assumptions and the observed estimate. They should not be read as the trial’s intended sample size, a justification for enrollment, or a statement about the probability that a finding is true. The registry does not report the original sample-size justification or whether any interim analyses were planned or performed. The crossover design and the baseline labeling also mean that the posted illustration should not be taken as a substitute for a design-specific calculation for a repeated-measures comparison.

11. Confidence Intervals and Precision

Precision concerns how tightly the available data locate an estimated effect. For the primary result, the posted risk difference is 0.0 and the confidence limits are both 0.0. Taken literally, that interval has no width. However, the endpoint is described as a baseline composite, and the registry does not explain the zero-valued result or provide analysis details. The interval should be reported as recorded, while recognizing that the registry record does not provide enough information to evaluate how it was generated or whether it reflects the intended endpoint definition.

For baseline knowledge, the posted mean difference is 0.4. Its confidence interval extends from -0.291 to 1.091 in the registry result. The interval includes zero and spans both negative and positive differences. This indicates uncertainty about the direction and size of the baseline difference under the reported analysis. The interval does not establish that the groups are equivalent; it indicates that the reported estimate is imprecise enough to include a range of possibilities around zero.

General interpretation of a confidence interval depends on the analysis assumptions. In this study, the registry does not report whether the estimates account for repeated observations, clinic-level clustering, or other design features. The method used to calculate the intervals is also not reported. Therefore, the numerical limits can be described, but the adequacy of the uncertainty calculation cannot be independently assessed from the registry record.

The displayed planning illustrations are conditional estimates based on the observed knowledge difference and stated assumptions. Their size reflects the small observed effect used in those calculations; it is not a measure of the precision achieved by this trial and not a report of observed power. The registry does not report a sample-size rationale for the completed study. Overall, the posted precision information is limited: the primary interval is reported without explanatory analysis detail, and the secondary interval is compatible with differences in either direction.

12. Multiplicity, Missing Data and Analysis Populations

Multiplicity arises when several outcomes, time points, or comparisons are examined. Even if each test uses a conventional threshold, examining many tests can increase the chance that at least one appears noteworthy by chance. Trial analysis plans commonly address this by identifying a primary endpoint, ordering hypotheses, or adjusting inference. The registry record identifies a primary measure and lists a secondary knowledge outcome, including a repeated listing of the same outcome name. It does not report a multiplicity strategy, testing hierarchy, or adjustment for multiple comparisons.

The registry lists 0 reported analyses. It nevertheless includes numerical arm summaries and a secondary unadjusted p-value. No further inferential results or analysis specifications are reported. The record does not say whether the posted summaries were prespecified, whether other analyses were performed but not entered, or whether any adjustment was considered. In the absence of those details, the secondary comparison should be interpreted cautiously and should not be treated as confirmatory evidence.

Missing-data handling is also not reported in the registry record. The posted arm counts are 64.0 and 54.0, while the enrollment entry is 120. The record does not explain the relationship between those entries, whether all participants completed each period, how missing survey responses were handled, or whether participants with incomplete data were excluded. The registry also does not describe an analysis population, such as an intention-to-treat or per-protocol population. It is therefore not possible to assess from the record whether the posted summaries include all randomized participants or only participants with available measurements.

For a crossover study, it is generally important to consider how outcomes from different periods are linked, whether period or sequence effects are relevant, and how incomplete follow-up affects within-participant comparisons. The registry does not report these methods. The timing and design details needed to interpret a treatment-period contrast are also not available in the posted results. These omissions limit both the assessment of bias and the interpretation of precision.

Interim analyses and any associated decision rules are not reported in the registry record. The original sample-size justification is also not reported. The planning illustrations based on the observed knowledge effect do not fill these gaps: they are planning calculations, not evidence of the original protocol or of observed power.

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

The posted results describe baseline summaries recorded for a randomized crossover study of a patient decision aid in rural primary care. They do not establish that the decision aid improved or failed to improve lung cancer screening adherence, shared decision-making, smoking cessation services, or patient knowledge. The primary endpoint is explicitly labeled as a baseline survey measure, and the secondary knowledge result is also labeled as baseline. An intervention-period estimate or a comparison of change over time is not reported in the registry record.

The primary value and comparison are recorded as zero, with confidence limits also recorded as zero. The registry describes a composite based on three survey questions, but it does not explain how the posted zero values correspond to the composite’s scoring or threshold. That reporting gap makes it especially important not to translate the zero summary into a broader claim about the care delivered or participants’ experiences.

The secondary knowledge estimate is a modest positive difference in the posted means, but its interval includes zero and the unadjusted p-value is 0.257. It is a baseline comparison, not an estimate of the effect of the decision aid. It also cannot be interpreted as proof that the groups were the same. The result is compatible with uncertainty about both the size and direction of the difference under the reported analysis.

More generally, a registry summary is not a full statistical report. The record does not provide the analysis method, missing-data approach, population definition, or handling of the crossover structure. Without those details and intervention-period results, the posted estimates cannot answer the main causal question. This is a limitation of what can be concluded from the registry record, not a claim about results that may exist elsewhere.

The trial’s completed status indicates that the registry reports the study as completed. Completion alone does not establish that every planned analysis or outcome is available in the record. The most defensible interpretation is therefore descriptive: the registry contains baseline summaries and a secondary unadjusted comparison, while the intervention effect on the outcomes of interest is not reported in the registry record.

14. Why This Trial Matters Statistically

This trial raises several statistical issues that are important in applied clinical research. First, the study is described as a randomized crossover design, yet the posted primary and secondary results are labeled baseline. The distinction between baseline description and an intervention-period comparison is essential: a baseline summary can characterize starting measurements but cannot show what changed after treatment exposure.

Second, the primary endpoint is a composite process measure derived from survey responses. Composite outcomes can summarize several related actions, but their interpretation depends on clear definitions of the component questions, scoring, and threshold. The registry describes the questions and a count of “Yes” responses but does not explain how that definition maps to the posted zero values. This illustrates why transparent outcome reporting matters alongside a numerical estimate.

Third, crossover studies require analysis methods that reflect repeated observations and timing. Random allocation is valuable, but the statistical interpretation also depends on how period, sequence, within-participant correlation, and possible clinic clustering are handled. These methods are not reported in the registry record. Readers therefore cannot determine whether the posted estimates represent the intended design-based contrasts.

Finally, uncertainty and multiplicity need context. The knowledge comparison is unadjusted and baseline, while the registry lists no reported analyses or multiplicity plan. The planning illustrations are not observed power and do not document the original sample-size rationale. Together, these features show why statistical interpretation should distinguish descriptive results, planned inference, and causal effect estimates. The record supports discussion of the posted summaries, but not a conclusion about the intervention’s effect.

15. 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.

Several limitations are specific to the available record. The primary endpoint is titled as a baseline survey measure, even though the trial description includes a later intervention period. The registry does not report a corresponding post-intervention result, a change estimate, or a treatment-period contrast. This prevents direct assessment of whether the primary adherence measure differed after introduction of the patient decision aid.

The primary measure is described as a composite of “Yes” responses to three questions, but the registry does not report how the resulting score was categorized or how the zero-valued arm results should be interpreted. Survey development and validation details are also not reported. The primary estimate is therefore difficult to connect fully to the intended construct of adherence.

The record identifies the study as randomized and crossover but does not report sequence allocation, period-specific methods, handling of repeated measurements, or adjustment for clinics. The analysis population and missing-data approach are not reported. The arm counts attached to the result differ from the enrollment entry, but the record does not explain the relationship or provide participant flow. These gaps limit assessment of selection, attrition, and analysis bias.

The knowledge result is a baseline comparison and is unadjusted. The registry does not report a multiplicity plan, a sample-size justification, or interim analysis procedures. It lists no reported analyses despite including an unadjusted comparison. The record also repeats the named secondary outcome without explaining whether the entries refer to different time points or measures. These limitations concern what the registry record allows readers to evaluate; they do not establish that the underlying study lacked such procedures or analyses.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Shared Decision Making in Rural Primary Care Lung Cancer Screening and Smoking Cessation — NCT04897568.
• Registry record last updated 2024-10-15; status last verified 2024-09.
• Results first posted 2024-10-15.
• 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.

19. Record Summary

NCT04897568 is a completed randomized, unmasked crossover study sponsored by the University of Colorado, Denver. It evaluates a patient decision aid in rural primary care in the context of lung cancer screening and smoking cessation. The registry records enrollment of 120, a start date of 2020-07-15, and a primary completion date of 2023-04-30.

The primary endpoint is a baseline survey composite intended to represent visit adherence to lung cancer screening guidelines and Centers for Medicare and Medicaid Services coverage criteria. The posted primary values are 0.0 for both listed groups, with a risk difference of 0.0. The secondary knowledge outcome is also labeled baseline; its posted mean difference is 0.4, with an unadjusted p-value of 0.257 and a confidence interval that includes zero.

The registry does not report intervention-period estimates, the analysis method, missing-data handling, or the original sample-size justification. The available results support a descriptive reading of baseline summaries, not a conclusion about the effect of the patient decision aid.