Gout in the ED and Improving Research Participation: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Gout in the ED and Improving Research Participation (NCT04075903), a randomized na study. The primary outcome is Outpatient Primary Care or Specialist Visits for Gout Treatment.

2. Clinical Question

The primary outcome is a count of participants who attended a qualifying outpatient visit, expressed in the registry record as a proportion. The posted counts are 64 participants in the intervention group and 35 in the control group. The accompanying comparison estimates describe the difference between groups, but they do not establish why an individual did or did not attend.

The trial's brief summary describes an emergency department-led project intended to improve gout care during acute exacerbations and over the longer term. A secondary project goal was to enhance minority participation in biomedical research in the Deep South. Those broader aims provide context, but the posted primary outcome specifically concerns outpatient visits for gout treatment. The registry record does not report a primary outcome measuring gout knowledge, flare prevention, treatment uptake, or research participation.

3. Trial Design

The registry record describes a completed, randomized, parallel-group trial with no masking. The intervention arm received the storytelling intervention, while the control arm received usual care. The intervention is described as a culturally adapted, health literacy-appropriate tablet-based program. The record lists gout as the condition and University of Alabama at Birmingham as the sponsor.

The recorded enrollment is 200. The outcome data are reported separately for the intervention and control groups, with 135 participants listed for the intervention outcome and 65 for the control outcome. The record does not explain the allocation process, why the group sizes differ, or whether the outcome denominators represent all randomized participants or a subset with available outcome data. The allocation method beyond the label “randomized” is not reported in the registry record.

The study start date is 2021-06-01, and the primary completion date is 2024-09-20. The status is completed. The phase is listed as NA. The registry record lists one outcome measure and no analysis records. It does, however, include a primary outcome result and a group comparison summary. Additional outcomes, participant flow, baseline characteristics, and details of follow-up procedures are not reported in the registry record.

The primary outcome timeframe is 3 months. The result concerns attendance at a primary care or specialist visit for gout treatment. No masking was used, so the record does not indicate that participants or study staff were blinded to group assignment. Details of how visits were ascertained, whether outcome assessment was independent, and how any departures from the assigned intervention were handled 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 Outpatient Primary Care or Specialist Visits for Gout Treatment, measured over 3 months.

The primary endpoint records whether a participant attended a primary care or specialist visit for gout treatment within 3 months. The registry describes the outcome as a proportion of participants and reports the number meeting that outcome in each group. The posted counts are 64 in the intervention group and 35 in the control group.

Attendance is a binary outcome at the participant level: each participant either is or is not counted as having the specified visit during the stated timeframe. It is therefore different from outcomes that measure the number of visits per participant, changes in symptoms, or medication use. The registry record does not report those measures as primary outcomes.

As a general statistical rationale, a visit-attendance endpoint can describe whether participants engaged with outpatient care after an intervention. It offers a concrete measure that can be compared between randomized groups. It does not, on its own, explain the reasons for attendance or nonattendance, indicate the quality of the visit, or measure subsequent health outcomes. Nor does attendance alone establish whether the storytelling intervention changed knowledge or long-term treatment decisions.

The endpoint description does not specify how qualifying visits were verified, whether different kinds of specialist visits were treated identically, or how missing follow-up information was classified. Those measurement and handling details are not reported in the registry record. Interpretation should therefore stay close to the recorded outcome: attendance at a qualifying outpatient visit for gout treatment within 3 months.

7. Results Posted in the Registry

• Intervention: 47.4% (64/135) versus 53.8% (35/65) on control; risk difference -6.4 percentage points (95% CI -21.2 to 8.3), risk ratio 0.88 (0.66–1.17); unadjusted two-proportion z-test p = 0.394.

8. Statistical Interpretation

9. Statistical Methods Explained

The primary outcome is binary at the participant level: the recorded event is attending a qualifying outpatient visit for gout treatment within 3 months. For a binary outcome, the analysis can compare the proportions with the event in the randomized groups. The registry reports both participant counts and a comparison expressed as a risk difference, alongside a risk ratio and an odds ratio.

What does the risk difference describe?

The risk difference is the intervention-group event proportion minus the control-group event proportion. The reported estimate is -0.064. A negative estimate means the observed proportion was lower in the intervention group for this coding of the comparison. The 95% confidence interval runs from -0.212 to 0.083, including zero. In general, zero is the no-difference reference for a risk difference. Because the interval crosses that reference, the posted estimate does not pin down the direction of the underlying difference.

A risk difference is an absolute measure: it expresses the gap between proportions on the probability scale. It can help communicate how far apart the observed groups are in absolute terms. It is distinct from a relative measure, which describes one group in relation to the other. The registry record does not report a clinically important threshold for interpreting the size of this risk difference.

How do the risk ratio and odds ratio differ?

The risk ratio compares the event proportions between the groups. The reported risk ratio is 0.880, and its 95% confidence interval is 0.661 to 1.173. The odds ratio compares the odds of the event rather than the proportions themselves. The reported odds ratio is 0.773, with a 95% confidence interval from 0.427 to 1.398. For either ratio, a value at the no-difference reference represents equal event frequency between groups on that scale. Both intervals include that reference. Odds and risks are related but are not the same quantity, so their numerical estimates need not match.

What does the p-value add?

The unadjusted p-value is 0.394. In general, a p-value summarizes how unusual data at least as discrepant as those observed would be under a specified no-difference model and its assumptions. It is not the probability that the no-difference model is true, and it does not tell readers the probability that the result will replicate. It also does not express the magnitude of the observed difference. The registry record does not report an adjusted p-value or a fuller analysis specification.

“Unadjusted” indicates that the reported comparison is not presented as adjusted for other variables. The record does not state whether the sponsor conducted additional analyses outside the displayed registry result. It lists no analysis records, and the statistical plan, model details, and analysis population definitions are not reported in the registry record. Consequently, the group comparison should be read as the posted unadjusted summary, not as evidence that particular covariates were considered or ruled out.

Why does randomization matter, and what is not known?

In general, random assignment aims to make groups comparable on average with respect to factors that could affect an outcome. It supports a group comparison, but it does not guarantee that every characteristic is balanced in a particular trial. Assessment of balance would require participant characteristics, which are not reported in the registry record. The record identifies the allocation as randomized, but the sequence-generation method, concealment procedures, and implementation details are not reported.

The record also does not report how missing outcome information was handled, whether the primary analysis followed assigned groups, or how visits were verified. These details matter because they define which participants contribute to an estimate and how the binary event is classified. No conclusions about these procedures can be drawn from the posted comparison alone.

As a general point, confidence intervals combine an estimated effect with information about its precision under the model used. They show a range of effect values compatible with the data and assumptions, rather than a guaranteed range for the true effect. The registry record provides intervals for the risk difference, risk ratio, and odds ratio, but does not provide enough analysis detail to reconstruct all modeling and data-handling decisions.

10. Confidence Intervals and Precision

The risk-difference estimate is -0.064, with a 95% confidence interval from -0.212 to 0.083. This interval crosses zero, the no-difference reference for an absolute difference, and includes values on both sides of it. The interval therefore reflects uncertainty not only about the size of the difference but also about its direction. It does not establish that the groups were identical.

The relative estimates also have intervals that include their no-difference reference values: the risk ratio is 0.880, with a 95% confidence interval from 0.661 to 1.173, and the odds ratio is 0.773, with a 95% confidence interval from 0.427 to 1.398. The intervals extend across values consistent with lower and higher event frequency in the intervention group, depending on the measure.

In general, a confidence interval describes uncertainty around an estimate under the statistical method and assumptions used. It is not a statement that the true value has a 95% probability of lying in the particular interval after the data have been observed. A narrower interval would indicate greater precision, while a wider interval allows a broader range of compatible effects.

The registry record does not report the analysis plan, missing-data procedures, or details of outcome ascertainment, all of which can affect interpretation of precision. The posted interval is the uncertainty summary for the displayed comparison; it does not account for every source of uncertainty that may arise from study conduct or outcome measurement.

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 sample-size figures are planning illustrations based on the observed effect, not the trial's own original design assumptions. The registry record's 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 specified as a fraction of the observed effect. These assumptions describe the planning calculation; the trial's own sample-size justification and original design assumptions are not reported in the registry record.

The figures are participants per arm, not total participants and not total events. The 80% power column describes the participant count per arm for a planning scenario with an 80% chance of detecting the specified effect under the calculation assumptions. The 90% power column gives the corresponding count for a 90% chance. These are prospective design quantities, not measures of how much power the completed trial had after observing its results. This is not observed power.

The rows consider planning for 100% of the observed effect, 75% of the observed effect, and 50% of the observed effect. The listed participant requirements rise as the assumed effect becomes smaller: detecting a smaller difference generally requires more participants for the same target power, all else held constant. For example, the registry's figures for planning for 75% of the observed effect are 1,681 participants per arm for 80% power and 2,249 participants per arm for 90% power. These are illustrations, not recommendations for a future study.

The observed effect is itself uncertain, as reflected in its confidence interval. A planning calculation that uses an observed estimate can therefore be sensitive to that estimate and to the stated assumptions. The sample-size figures do not establish that the original trial was designed around these assumptions, and the registry record does not report the trial's own design calculation.

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, p₀ and p₁ are the control and treatment proportions, and p̄ is their average.

Worked calculation for this trial

1. Control proportion p₀ = 0.538; treatment proportion p₁ = 0.474; average p̄ = 0.506.
2. First term: z_1−α/2 × √[2p̄(1−p̄)] = 1.96 × 0.7071 = 1.3858.
3. Second term: z_1−β × √[p₀(1−p₀) + p₁(1−p₁)] = 0.842 × 0.7056 = 0.5938.
4. n = (1.3858 + 0.5938)² / (-0.0644)² = 945.3, rounded up to 946 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
p0 <- 0.538461538461538                          # control proportion
p1 <- 0.474074074074074                          # treatment proportion
n_per_arm <- function(power, frac = 1) {
  q1 <- p0 + (p1 - p0) * frac               # smaller effect = fraction of the observed difference
  pbar <- (p0 + q1) / 2
  z_b <- qnorm(power)
  ceiling(round((z_a * sqrt(2 * pbar * (1 - pbar)) + z_b * sqrt(p0 * (1 - p0) + q1 * (1 - q1)))^2 / (q1 - p0)^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 (unrounded n per arm)
cat("power.prop.test:", round(power.prop.test(p1 = p0, p2 = p1, power = 0.80)$n, 1), "\n")

# Simulation: how often does the z-test reject at the 80%-power sample size?
set.seed(4075903)
n    <- n_per_arm(0.80)
reps <- 20000
x0 <- rbinom(reps, n, p0); x1 <- rbinom(reps, n, p1)
ph <- (x0 + x1) / (2 * n)
z  <- ((x1 - x0) / n) / sqrt(ph * (1 - ph) * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(z) > z_a, na.rm = TRUE), reps))

Output from running the code

100% of observed effect: n per arm = 946 (80% power), 1,265 (90% power)
 75% of observed effect: n per arm = 1,681 (80% power), 2,249 (90% power)
 50% of observed effect: n per arm = 3,778 (80% power), 5,057 (90% power)
power.prop.test: 945.3 
Simulated power at n = 946 per arm: 0.803 (20000 replicates)

The simulation draws many pairs of event counts at the planned sample size and counts how often the two-proportion z-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 one outcome measure, identifies it as the primary outcome, and lists no secondary outcomes. It also lists no analysis records. The comparison summary includes an unadjusted p-value for the primary outcome, but the registry record does not report a statistical analysis plan or a multiplicity procedure.

Multiplicity arises when several outcomes, time points, subgroups, or statistical tests are examined. In general, conducting many tests can increase the chance of observing an apparently notable result by chance. Whether that issue arose in this trial cannot be determined from the registry record: it does not describe additional analyses, subgroup tests, or interim analyses. No such procedures should be assumed.

The outcome data list 135 participants for the intervention group and 65 for the control group. The record does not clarify whether these are all randomized participants, participants with available primary-outcome data, or another analysis population. It does not report participant flow, exclusions from analysis, withdrawals, or the number with missing outcome data. As a result, the analysis population and follow-up completeness cannot be established from the posted information.

Missing-data handling is also not reported in the registry record. The record does not say whether a participant without documented visit information was treated as not attending, excluded from the analysis, or handled through another method. These choices can affect a binary attendance estimate, so the posted counts should be interpreted without assuming a particular approach.

The registry record identifies the trial as randomized but does not describe whether the primary analysis retained participants in their assigned groups. It also does not report adjustment for baseline characteristics or other covariates. The posted comparison is labeled unadjusted; further details about analysis populations and alternative models are not reported in the registry record.

14. 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 serious adverse event figures report zero serious adverse events in the intervention group among 135 participants at risk and zero in the control group among 65 participants at risk. The other adverse event figures are also zero in each group, and the recorded deaths are zero in each group. These are the registry's reported counts for the listed at-risk groups.

A zero count means no events of that category were recorded in the posted results; it does not establish that the underlying risk is zero. In general, safety counts are interpreted in the context of the number monitored, the duration and completeness of monitoring, and how events were defined and collected. Those details, including the event collection procedures and the duration of safety follow-up, are not reported in the registry record.

The registry record lists no serious adverse event terms. The absence of listed terms should not be read as evidence about events beyond the posted categories and counts. These figures describe reported safety events; they do not support a broader conclusion about safety in other populations or settings.

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

The posted primary outcome describes attendance at a primary care or specialist visit for gout treatment within 3 months. The counts are 64 participants in the intervention group and 35 in the control group. The unadjusted risk-difference estimate is -0.064, with a 95% confidence interval from -0.212 to 0.083. This indicates that the observed attendance proportion was lower in the intervention group for the stated comparison, while the interval remains compatible with differences in either direction.

The risk-ratio and odds-ratio estimates offer alternative descriptions of the same binary outcome. Their confidence intervals also include their respective no-difference reference values. The unadjusted p-value is 0.394. Taken together, these summaries show an uncertain comparison rather than a precisely determined difference. They do not establish that the groups had equal attendance, nor do they establish a difference in a particular direction.

The outcome is a measure of outpatient visit attendance, not a direct measure of gout symptoms, flare prevention, medication use, knowledge, or long-term health. The registry record does not report results for those measures. The project summary describes broader aims involving care and minority participation in biomedical research, but the posted primary outcome does not quantify those broader aims.

The record identifies a randomized comparison, which is relevant to interpreting group differences, but key details are not reported: participant characteristics, allocation procedures, outcome ascertainment, missing-data handling, and the analysis population. The posted result therefore should be read in the scope of the recorded endpoint and its stated timeframe, without assuming unreported methods or extending the finding to outcomes that were not posted.

16. Why This Trial Matters Statistically

This trial illustrates how a behavioral intervention can be evaluated using a concrete engagement outcome: attendance at an outpatient visit for gout treatment. The intervention was designed around storytelling, health literacy, and cultural adaptation, while the primary endpoint captured whether participants attended qualifying care within 3 months. Keeping the intervention's aims separate from the measured endpoint is important: a visit outcome does not itself measure knowledge, treatment decisions, or longer-term health.

The registry comparison also shows why effect estimates and their uncertainty should be read together. The risk-difference estimate has a negative direction, but its confidence interval includes zero and extends to positive values. The relative measures have similarly inclusive intervals. The posted data thus leave substantial uncertainty about the direction and magnitude of the attendance difference.

Several details needed for a fuller statistical assessment are not reported in the registry record, including participant characteristics, outcome ascertainment, missing-data handling, and the analysis population. Their absence limits assessment of how the endpoint was measured and which participants contributed to the comparison. It also cautions against treating a single unadjusted estimate as a complete account of the trial.

Finally, the registry presents planning illustrations based on the observed effect, alongside the completed trial results. Distinguishing prospective planning quantities from observed outcomes prevents the planning figures from being mistaken for evidence about the trial's achieved power. Together, these statistical considerations help keep interpretation aligned with the outcome actually reported and the uncertainty around its estimate.

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 provides a limited account of trial conduct and analysis. It identifies a randomized, unmasked, parallel-group design, but does not describe sequence generation, allocation concealment, or implementation of randomization. The participant characteristics needed to assess group balance and the population to which the findings might apply are not reported in the registry record.

The recorded outcome concerns attendance within 3 months, but the method used to identify or verify visits is not reported. The record does not explain how missing visit information was handled, whether all randomized participants contributed to the outcome analysis, or whether there were withdrawals or exclusions. The listed outcome group sizes therefore cannot be interpreted as a complete participant-flow account.

The registry record includes an unadjusted comparison and no analysis records. It does not report a statistical analysis plan, adjusted results, subgroup analyses, interim analyses, or multiplicity handling. The record also does not report a sample-size justification for the trial's original design; the listed planning illustrations are based on the observed effect and stated calculation assumptions.

Only the primary attendance outcome is listed, and no secondary outcomes are posted. The record does not provide results for gout knowledge, flare prevention, treatment uptake, or broader research participation. The safety figures contain zero events in the listed categories, but event definitions, ascertainment methods, and monitoring duration are not reported. These limitations constrain interpretation to the posted counts and comparison rather than broader claims about intervention effects, safety, or applicability.

18. Related Tutorials

19. Related Statistical Calculators

20. Sources

• ClinicalTrials.gov: Gout in the ED and Improving Research Participation — NCT04075903.
• Registry record last updated 2026-10-23; status last verified 2026-10.
• Results first posted 2025-12-03.
• 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

The registry record describes a completed, randomized, parallel-group trial with no masking, sponsored by University of Alabama at Birmingham. It lists gout as the condition, enrollment of 200, a start date of 2021-06-01, and a primary completion date of 2024-09-20. The phase is listed as NA.

The intervention was a tablet-based storytelling program compared with usual care. The primary outcome was attendance at a primary care or specialist visit for gout treatment within 3 months. The posted counts are 64 in the intervention group and 35 in the control group. The unadjusted risk difference is -0.064, with a 95% confidence interval from -0.212 to 0.083 and an unadjusted p-value of 0.394.

The registry record lists no secondary outcomes or analysis records. It does not report the original sample-size justification, participant characteristics, missing-data procedures, or detailed analysis plan.