Corticosteroid Pulse After Ablation: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Corticosteroid Pulse After Ablation (NCT00807586), a randomized phase 4 study. The primary outcome is Number of Participants With Clinically Significant Atrial Arrhythmias at 6 Weeks.

2. Clinical Question

3. Trial Design

The registry record describes a completed Phase 4 randomized trial titled “Corticosteroid Pulse After Ablation,” with the official title “SAAB: Randomized, Double Blind STudy of Corticosteroid Pulse After Ablation.” It lists atrial fibrillation as the condition, Minneapolis Heart Institute Foundation as the sponsor, and enrollment of 119. The recorded start is 2008-12 and the primary completion is 2009-12. These are registry entries; they do not by themselves describe the timing of every participant’s treatment or follow-up.

The design is recorded as randomized, parallel-group, and quadruple-masked. The intervention entries identify Solumedrol and placebo, while the arm descriptions identify Steroid and Placebo. The brief study description says patients were randomized to receive intravenous steroids or not immediately following ablation. The registry does not report the randomization method, allocation concealment procedures, masking roles, treatment dose, or treatment adherence. Those details should not be inferred from the design labels alone.

For the primary outcome, the posted group results each use 58 participants: 4 in the Steroid group and 12 in the Placebo group had the defined event. The registry separately notes 3 patients lost to follow-up, but does not explain how missing outcome information was handled or how the loss was distributed by group. Safety data use different at-risk counts, 60 for Steroid and 59 for Placebo. These denominators pertain to different reported outcomes and should not be treated as interchangeable.

The primary outcome timeframe is 6 weeks. A secondary result for repeat intervention is recorded at 3 months. Although cardiac pain assessment and symptoms requiring diuretic are also named as secondary outcomes, their results are not reported in the registry record. The record does not report the trial’s original sample-size justification, detailed statistical analysis plan, or analysis populations.

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

Analysis population for the primary outcome, as defined in the registry: 3 patients lost to follow-up

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 Number of Participants With Clinically Significant Atrial Arrhythmias at 6 Weeks, measured over 6 weeks.

The primary endpoint is the number of participants with clinically significant atrial arrhythmias at 6 weeks. The registry’s definition focuses on events that prompted clinical care or a treatment change: emergency-room, urgent-care, or hospital care for atrial fibrillation; cardioversion for atrial fibrillation; or atrial fibrillation requiring an increase in anti-arrhythmia medication. This is a count of participants with an event, rather than a count of all episodes. A participant meeting more than one part of the definition is not necessarily represented as multiple events in this measure.

Such an endpoint can capture clinically consequential recurrence during the early post-ablation period, while avoiding reliance only on symptoms that may not lead to care. It is also narrower than any recurrence of atrial fibrillation: episodes that did not meet the listed criteria are outside the stated definition. The outcome is assessed at 6 weeks, so it does not by itself describe longer-term rhythm outcomes.

The registry reports 4 participants with the endpoint in the Steroid group and 12 in the Placebo group, with 58 participants recorded in each group for this outcome. It notes 3 patients lost to follow-up but does not report the missing-data procedure. The registry also does not report endpoint adjudication procedures or whether event assessors were masked. These omissions limit how fully the endpoint’s ascertainment and analysis can be evaluated.

7. Results Posted in the Registry

• Steroid: 6.9% (4/58) versus 20.7% (12/58) on control; risk difference -13.8 percentage points (95% CI -26.1 to -1.5), risk ratio 0.33 (0.11–0.97); unadjusted two-proportion z-test p = 0.031.

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.

Repeat Intervention

• Endpoint type: Binary: the number of participants with the event, compared as proportions.
• Test: Unadjusted two-proportion z-test, with a Wald 95% confidence interval for the risk difference.
• Result:
  • Steroid: 4.0% (2/50) versus 14.5% (8/55) on control; risk difference -10.5 percentage points (95% CI -21.3 to 0.2), risk ratio 0.28 (0.06–1.23); unadjusted two-proportion z-test p = 0.066.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Steroid and the control. The interval gives the range of effects that remain compatible with the data.

The registry names cardiac pain assessment, symptoms after ablation requiring diuretic, and repeat intervention as secondary outcomes. A result is posted for repeat intervention at 3 months, while results for cardiac pain and symptoms requiring diuretic are not reported in the registry record. The secondary evidence is therefore incomplete: the available result cannot represent the full pattern across every named secondary outcome.

The repeat-intervention estimate points in the same direction as the primary comparison, but its confidence interval includes no difference and its unadjusted p-value is 0.066. Directional agreement can be noted, but it does not turn the secondary finding into a replication of the primary result. The outcomes differ in definition and timeframe, and the registry does not report an analysis plan describing how they were intended to support or qualify the primary comparison.

General statistical explanation: when multiple outcomes are examined, the chance of seeing an apparently notable result by chance can increase. Whether and how to account for this depends on the prespecified testing strategy and the relationship among outcomes. The registry record does not report a multiplicity adjustment or a testing hierarchy. In the absence of those details, unadjusted secondary results carry less weight than a clearly specified primary comparison and should be treated as exploratory rather than as definitive evidence.

Missing secondary results also matter to interpretation. Without results for the other named measures, it is not possible to assess whether the overall pattern is consistent across symptoms, treatment-related outcomes, and repeat intervention. The registry does not report why those results are absent or whether they were collected but not posted. The available secondary evidence can describe only the posted repeat-intervention comparison, not a comprehensive benefit or harm profile.

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

• Cardiac Pain Assessment
• Symptoms Post Ablation Requiring Diuretic
• Repeat Intervention

9. Statistical Interpretation

10. Statistical Methods Explained

The registry presents the primary outcome as a binary participant-level measure: each group’s result is the number of participants meeting the event definition, alongside the number recorded for that outcome. General statistical explanation: a binary outcome distinguishes whether a participant did or did not meet a defined criterion. It does not describe how many times an event occurred in a participant, unless the outcome is specifically defined as an episode count. Here, the registry labels the outcome as a count of participants.

What does the risk difference express?

General statistical explanation: a risk difference compares the proportion with an outcome in one group with the proportion in another group. A value below zero means the first group’s observed proportion is lower when the contrast is defined as first group minus comparison group; a value above zero means it is higher. The primary comparison is coded for Steroid relative to Placebo and reports a risk difference of -0.138. This is an unadjusted estimate based on the posted group summaries. It is not an adjusted estimate that accounts for participant characteristics or other variables.

A risk difference is expressed on the probability scale and can be useful for understanding the absolute separation between groups. Its meaning depends on the outcome definition, timeframe, and direction of the contrast. It should be interpreted together with the confidence interval, which indicates the uncertainty around the estimate under the method used. The registry record does not identify a confidence-interval method or report an adjusted model for this endpoint.

How should the p-value be understood?

General statistical explanation: a p-value measures how incompatible the observed data are with a specified null hypothesis under the statistical model used. It is not the probability that the null hypothesis is true, and it does not measure the size or clinical importance of an effect. The primary unadjusted p-value is 0.031. The registry does not report a full statistical analysis plan, so the comparison should be read as the posted unadjusted result rather than as evidence that every design or analysis decision is known.

The secondary repeat-intervention comparison has an unadjusted p-value of 0.066. This value should be considered alongside its confidence interval and the fact that it is a secondary outcome. A p-value just above or below a conventional threshold does not create a sharp boundary between certainty and uncertainty. The estimate and its interval are important for understanding the range of effects compatible with the data.

Why do event counts and group sizes matter?

General statistical explanation: estimates based on fewer observed events tend to be less precise, because a small change in event counts can substantially affect the estimated group contrast. The primary analysis records 4 events in the Steroid group and 12 in the Placebo group. Its interval reflects uncertainty rather than asserting that the point estimate is exact. The denominator for this endpoint is 58 participants in each group. Safety outcomes use different at-risk denominators, so their counts cannot be substituted into the primary analysis.

The registry states that 3 patients were lost to follow-up for the primary outcome, but it does not report how missing information was addressed. General statistical explanation: missing outcome data can affect an estimate if the chance of being observed is related to outcome status or differs between groups. Without a stated handling method or group-specific accounting, the impact cannot be evaluated from the registry record alone.

What do relative measures add?

General statistical explanation: a relative risk compares the outcome proportions between groups as a ratio, while an odds ratio compares the odds. The posted primary relative risk is 0.333, with interval 0.114 to 0.973; the posted odds ratio is 0.284, with interval 0.086 to 0.941. These measures express the contrast on different scales from the risk difference and are also unadjusted. They do not replace the absolute group counts or resolve uncertainty about endpoint ascertainment and missing data.

The registry does not report a model specification, covariate adjustment, or detailed inferential procedure. No statistical analysis results are listed beyond the posted comparisons. Thus, the most transparent reading is to describe the recorded group outcomes, their unadjusted contrasts, and their uncertainty without attributing unreported analytic choices to the investigators.

11. Confidence Intervals and Precision

The primary risk-difference estimate is -0.138, with a 95% confidence interval from -0.261 to -0.015. General statistical explanation: a confidence interval gives a range of values that are compatible with the observed data under the method used to calculate the interval. It conveys uncertainty around an estimate; it is not a guarantee that the true value lies within the interval, nor does it describe the range of individual participant outcomes.

For this comparison, the entire reported interval is below zero. That aligns with the observed direction of the estimate, which is fewer recorded primary events in the Steroid group relative to Placebo under the registry’s coding. The interval nevertheless extends across a substantial range of possible risk differences. The point estimate should not be treated as a precisely known effect, especially given the recorded event counts of 4 and 12. The registry record does not report the interval calculation method or an adjusted confidence interval.

The primary relative risk is 0.333, with interval 0.114 to 0.973, and the odds ratio is 0.284, with interval 0.086 to 0.941. Both intervals are reported as not including the null value for their respective measures. These ratios communicate relative contrasts and should be read alongside the absolute risk-difference estimate and group counts. Ratios can appear more pronounced than absolute changes, so neither scale alone gives a complete account.

For repeat intervention, the risk-difference interval is -0.213 to 0.002, including zero. This indicates that the secondary estimate is compatible with effects on either side of no difference under the reported interval method. Across these outcomes, precision is limited by the available information; the registry record does not report additional analysis that would narrow or otherwise qualify the intervals.

12. Planning a Similar Trial: Sample Size

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

The sample-size figures are planning illustrations based on the observed effect, not the original trial’s sample-size justification. The registry record does not report the trial’s original design assumptions. The stated planning assumptions are a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. Each planning row uses the stated fraction of the observed effect. The figures are participants per arm, not total participants or total events.

For the primary endpoint, planning for 100% of the observed effect gives 97 participants per arm for 80% power and 130 participants per arm for 90% power. Planning for 75% of the observed effect gives 192 participants per arm for 80% power and 256 participants per arm for 90% power. Planning for 50% of the observed effect gives 470 participants per arm for 80% power and 629 participants per arm for 90% power.

In plain terms, the 80% power column gives an illustrative group size for a design that would have an 80% chance of detecting the specified effect under the stated assumptions, if that effect and model assumptions were correct. The 90% column gives the corresponding illustration for a higher chance of detection. Smaller effects need more participants to distinguish them from random variation, which is why the listed requirements rise as the assumed fraction of the observed effect gets smaller. These figures are not observed power; they are prospective planning illustrations.

The planning calculations concern the primary comparison. The repeat-intervention planning values are based on that secondary outcome’s observed estimate and should be interpreted with the same assumptions and limitations. The curve is a visual expression of how the required group size changes as the effect targeted for detection changes; it does not establish that the trial was designed using these calculations or that the assumptions match the original design.

13. How the Sample Size Is Derived

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

Formula

n is the number of participants in each arm, p₀ and p₁ are the control and treatment proportions, and p̄ is their average.

Worked calculation for this trial

1. Control proportion p₀ = 0.207; treatment proportion p₁ = 0.069; average p̄ = 0.138.
2. First term: z_1−α/2 × √[2p̄(1−p̄)] = 1.96 × 0.4877 = 0.9558.
3. Second term: z_1−β × √[p₀(1−p₀) + p₁(1−p₁)] = 0.842 × 0.4778 = 0.4021.
4. n = (0.9558 + 0.4021)² / (-0.1379)² = 96.9, rounded up to 97 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 <- 0.206896551724138                          # control proportion
p1 <- 0.0689655172413793                          # 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(807586)
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 = 97 (80% power), 130 (90% power)
 75% of observed effect: n per arm = 192 (80% power), 256 (90% power)
 50% of observed effect: n per arm = 470 (80% power), 629 (90% power)
power.prop.test: 96.9 
Simulated power at n = 97 per arm: 0.820 (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.

14. Multiplicity, Missing Data and Analysis Populations

The registry record does not report a statistical analysis plan describing the primary testing procedure, a hierarchy of outcomes, or any adjustment for multiple comparisons. It also does not report interim analyses or stopping rules. These omissions do not establish that such procedures were absent; they mean their use cannot be evaluated from the registry record. The primary comparison is posted as an unadjusted result, and no reported secondary analyses are listed.

Multiplicity is relevant because several outcomes are named, including cardiac pain assessment, symptoms requiring diuretic, and repeat intervention. General statistical explanation: testing multiple outcomes can increase the chance that at least one result appears noteworthy even when there is no underlying difference. Prespecifying which outcome is primary and how secondary tests will be interpreted can help control that risk. The available record identifies a primary outcome but does not explain whether multiplicity procedures were planned or applied. The secondary repeat-intervention result should therefore be interpreted cautiously, and the missing results for other named secondary outcomes leave the overall evidence incomplete.

For the primary endpoint, the registry notes 3 patients lost to follow-up. It does not describe whether these participants were excluded, counted through another procedure, or handled using any imputation or sensitivity analysis. Nor does it give group-specific missingness details. The primary outcome denominator is 58 in each group, but the registry does not explain how those denominators relate to the recorded losses. The impact of missing data on the comparison cannot be determined from the posted information.

The record does not specify whether the primary analysis was intention-to-treat, per-protocol, or based on another analysis population. It does not give a participant flow account or explain exclusions after randomization. Consequently, the relationship between randomized assignment and the analyzed groups is not fully documented. These gaps limit the ability to assess risks of bias arising from missing outcomes, exclusions, or departures from assigned treatment.

15. 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 3% reporting threshold.

Most frequent non-serious adverse event terms

The serious adverse-event figures report zero affected participants in each group: the Steroid group has 0 serious adverse events among 60 at risk, and the Placebo group has 0 among 59 at risk. This means no serious adverse events are recorded in these posted figures. The registry does not provide serious-event terms, and deaths are not reported in the registry record.

Other adverse events are reported for 25 participants among 60 at risk in the Steroid group and 17 among 59 at risk in the Placebo group. These are counts, not a description of event severity, duration, or whether events were considered related to treatment. The record does not provide the event types or a formal comparison of these other adverse events. It also does not state whether all adverse events were collected over the same period as the efficacy outcomes.

Safety denominators differ from the primary endpoint denominators, so they should be interpreted separately. Zero recorded serious events does not establish that serious harms are impossible or that risks are equivalent between groups. With the available registry information, the appropriate reading is limited to the adverse-event counts and at-risk groups as posted.

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

The primary posted comparison shows fewer recorded participants meeting the clinically significant atrial-arrhythmia definition in the Steroid group than in the Placebo group at 6 weeks. The unadjusted risk difference is -0.138, its 95% confidence interval is -0.261 to -0.015, and the unadjusted p-value is 0.031. These numbers describe the registry’s recorded outcome and comparison. They do not by themselves establish the magnitude that would be expected in other settings or populations.

The result is specific to a defined early outcome after ablation. It counts participants meeting criteria involving urgent or emergency care, hospitalization, cardioversion, or an increase in anti-arrhythmia medication. It does not measure every episode of atrial fibrillation, all symptoms, or rhythm status over longer follow-up. The registry also reports a repeat-intervention comparison at 3 months, but that secondary result is less conclusive and other named secondary outcomes have no results reported in the registry record.

Randomization and quadruple masking are features of the recorded design that are relevant to the comparison. However, the registry does not report details of the randomization procedure, masking roles, missing-data handling, or analysis populations. The primary outcome notes 3 patients lost to follow-up. Without further information, it is not possible to determine how missing observations or other post-randomization events affected the estimate.

The result should not be treated as proof that corticosteroid treatment will produce a particular outcome for an individual, nor does it establish all aspects of benefit and harm. The registry record provides an unadjusted comparison with uncertainty, not a complete clinical assessment. The appropriate conclusion is limited to the posted trial data, endpoint definition, follow-up timeframe, and information available about conduct and analysis.

17. Why This Trial Matters Statistically

This trial illustrates why an estimate should be read alongside its endpoint definition and follow-up period. “Clinically significant atrial arrhythmias” is not simply any recorded recurrence: the registry defines the endpoint through events leading to specified forms of care or a medication increase. That distinction affects what the result can represent. The primary comparison concerns this operational definition at 6 weeks, rather than all possible rhythm events or long-term outcomes.

The posted risk difference and confidence interval show both direction and uncertainty. A single p-value cannot communicate the range of effect sizes compatible with the data, while the confidence interval alone does not establish clinical importance. Considering group counts, absolute contrast, relative measures, and interval estimates gives a more complete statistical reading than focusing on a threshold alone.

The record also demonstrates the importance of transparent reporting. It gives a primary result and one secondary comparison, but does not report results for every named secondary outcome, details of the original sample-size justification, the statistical analysis plan, or the handling of missing primary outcomes. Those gaps matter when judging multiplicity, the analysis population, and the completeness of the evidence.

Finally, planning illustrations based on the observed effect are not a substitute for the trial’s original design assumptions. They help show how required sample size changes with the effect a future study aims to detect, but cannot establish what the original investigators planned. Keeping design information, observed results, uncertainty, and planning calculations distinct is essential to interpreting this trial accurately.

18. Limitations

• The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
• Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.

The registry record leaves several trial-specific limitations unresolved. It notes 3 patients lost to follow-up for the primary endpoint but does not report the group distribution of those losses or the method used to handle missing outcomes. The recorded primary denominators are 58 in each group, and the record does not explain how those denominators relate to loss to follow-up. This prevents a full assessment of missing-data bias.

Details needed to evaluate conduct are also not reported in the registry record. These include the randomization method, allocation concealment, the roles covered by quadruple masking, treatment dose, adherence, and endpoint adjudication procedures. The registry does not describe the analysis population or whether the primary comparison followed an intention-to-treat approach. No adjusted analysis or sensitivity analysis is reported.

The primary outcome is limited to clinically significant events during 6 weeks and does not capture all possible recurrences or later outcomes. The repeat-intervention result is reported at 3 months, but results for the other named secondary outcomes are not reported in the registry record. The record does not report a multiplicity procedure, so the secondary result’s evidential role is unclear.

The safety information is also limited: serious-event counts are zero in both groups, while other adverse events are given as aggregate counts without event terms or a reported comparison. Deaths are not reported in the registry record. The original sample-size justification, detailed statistical plan, and any interim analysis procedures are also not reported. These reporting gaps do not show that procedures were absent, but they constrain what can be concluded from the record.

19. Related Tutorials

20. Related Statistical Calculators

21. Sources

• ClinicalTrials.gov: Corticosteroid Pulse After Ablation — NCT00807586.
• Registry record last updated 2019-08-20; status last verified 2019-07.
• Results first posted 2019-08-20.
• Data retrieved from ClinicalTrials.gov on 2026-11-09.
• Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.

22. Record Summary

The registry record describes a completed Phase 4 randomized, parallel-group, quadruple-masked trial of intravenous Solumedrol versus placebo immediately following ablation for atrial fibrillation. Enrollment is recorded as 119. The primary outcome is the number of participants with clinically significant atrial arrhythmias at 6 weeks.

The posted primary counts are 4 among 58 participants in the Steroid group and 12 among 58 in the Placebo group. The unadjusted risk difference is -0.138, with a 95% confidence interval from -0.261 to -0.015 and an unadjusted p-value of 0.031. The registry notes 3 patients lost to follow-up but does not report how missing outcomes were handled.

A secondary repeat-intervention result is recorded at 3 months. Other named secondary outcomes have no results reported in the registry record. Serious adverse events are recorded for 0 participants in each group; other adverse events are reported for 25 in the Steroid group and 17 in the Placebo group. The registry does not report the original sample-size justification or a detailed statistical analysis plan.