Impact of Virtual Reality on Pre-procedural anxieTy Prior to Heart cathEterIzAtion - VR-THEIA: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Impact of Virtual Reality on Pre-procedural anxieTy Prior to Heart cathEterIzAtion - VR-THEIA (NCT03662607), a randomized na study. The primary outcome is Change in Anxiety Measured by the Sate-Trait Anxiety Inventory (STAI).

2. Clinical Question

This is a comparison of two assigned education approaches in a randomized, parallel-group trial. The primary question is about the difference in anxiety scores between the groups, not whether either group’s score represents a clinical diagnosis or a threshold for treatment. The registry record identifies one primary outcome measure. It does not report a posted secondary outcome measure or a registry analysis entry.

3. Trial Design

VR-THEIA was a randomized, parallel-group trial with no masking. The registry reports enrollment of 180 participants. The control arm received standard pre-procedural education for cardiac catheterization, while the treatment arm received that education plus a virtual reality experience. The registry lists the virtual reality experience as a behavioral intervention.

The trial began on 2017-04-18, reached primary completion on 2021-11-29, and is listed as completed. The registry does not report the original sample-size justification, the methods used to generate the random allocation sequence, concealment of allocation, or the timing of any interim analyses. Masking is listed as none; further details about who knew the assigned group are not reported in the registry record.

The primary outcome is described as change in anxiety measured by the STAI, from a baseline visit to procedure day. Baseline visits could occur up to 4 weeks before the procedure. The posted arm summaries list 91 participants in control and 89 in the VR group. They report means and standard deviations for the continuous outcome. The registry does not give an analysis population definition or explain whether the summaries include every randomized participant.

One primary outcome measure is listed, and no secondary outcome measure is posted. No registry analysis entry is posted. As a result, the record gives the outcome definition and group summaries but does not establish the full analysis plan or all procedures used to produce the reported comparison.

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 undergoing clinical cardiac catheterization, who voluntarily agreed to study participation

6. Primary Endpoint

The registry lists the primary outcome as Change in Anxiety Measured by the Sate-Trait Anxiety Inventory (STAI), measured over Change from baseline visit to procedure day. Baseline visits will occur up to 4 weeks prior to procedure..

The primary endpoint is described as change in anxiety from the baseline visit to procedure day, measured with the State-Trait Anxiety Inventory (STAI). The STAI is a 40-item self-report inventory using a 4-point Likert scale. It assesses state anxiety and trait anxiety. Scores range from 20 to 80, with higher scores corresponding to greater anxiety.

An anxiety score provides a standardized way to quantify a self-reported psychological experience. Measuring the outcome around the procedure allows the trial to compare anxiety in the period relevant to cardiac catheterization, while the baseline visit provides a reference point before the procedure day. The registry says that baseline visits occur up to 4 weeks before the procedure; it does not report the exact timing for individual participants or details of how the change score was calculated.

The endpoint is continuous, and the posted results are expressed as means with standard deviations. This allows the group averages and the estimated mean difference to describe the direction and size of the observed contrast, while also showing variation among participants. A group mean does not describe every participant’s experience, and the registry does not report additional distributional summaries or individual-level outcomes.

7. Results Posted in the Registry

• VR Group (Treatment): mean 65.71 versus 69.81 on control; difference -4.10 (95% CI -8.83 to 0.63), standardized effect d = -0.25; z-test p = 0.089.

8. Statistical Interpretation

9. Statistical Methods Explained

The registry describes a randomized, parallel-group comparison. Randomization is intended to make assigned groups comparable, on average, with respect to measured and unmeasured baseline characteristics. It does not guarantee that the groups will be identical in a particular trial, and randomization alone does not answer questions about missing observations, adherence, or how outcomes were analyzed. The record does not report the sequence-generation or allocation-concealment procedures.

What does a mean difference represent?

The primary outcome is continuous, so the reported contrast is a difference between group means. The estimate of -4.1 is for VR versus control: a negative value indicates a lower reported mean in the VR group. This is a summary of the contrast in group averages; it does not mean that every participant’s score changed by that amount. The group standard deviations, 17.11 in control and 15.22 in the VR group, describe spread around each arm’s mean.

The comparison also reports a pooled standard deviation of 16.2 and a standardized effect estimate of -0.253. A standardized effect expresses the mean contrast relative to a measure of outcome variability, which can help describe the size of a contrast on a scale that is less dependent on the outcome’s original units. It remains a summary of the observed comparison and should not be treated as a direct measure of clinical importance. The registry does not report a clinically important threshold for the STAI outcome.

How should the p-value be understood?

The unadjusted p-value is 0.089. In general, a p-value measures how compatible the observed data are with a null model, under the model’s assumptions. It is not the probability that the null hypothesis is true, and it does not measure the size or importance of an effect. The term unadjusted indicates that the posted value is not adjusted for multiplicity; the record does not describe any further testing strategy. No trial-specific decision threshold or full statistical analysis plan is reported in the registry record.

A p-value should be interpreted alongside the estimate and confidence interval, rather than on its own. Here, the interval from -8.828 to 0.628 includes zero. This reflects uncertainty about the direction and magnitude of the population contrast, even though the observed point estimate is negative. The registry analysis entry count is zero, so further methods that might clarify how the posted estimate was obtained are not available in the record.

Why does the confidence interval matter?

A confidence interval is a range produced by a statistical procedure that, over repeated samples under its assumptions, would contain the target parameter at the stated confidence level at the procedure’s nominal rate. For a reader, it communicates precision: a narrower interval indicates less uncertainty about the parameter than a wider interval, all else equal. It is not a guarantee that the true value lies in a particular interval, nor is it a range of individual participant outcomes.

The reported interval is compatible with both a negative and a positive mean difference. That makes the result inconclusive about the direction of the underlying contrast at the level captured by this interval. It does not establish equivalence or rule out a potentially important difference. Determining clinical importance would require a relevant threshold or context, neither of which is reported in the registry record.

What information about analysis is missing?

The registry identifies a mean outcome with standard deviation but does not describe the statistical test or model used for the sponsor’s result. The record does not report whether the comparison adjusted for baseline STAI score or other covariates, how incomplete observations were handled, whether the analysis followed assigned groups, or how deviations from the assigned intervention were treated. It also does not define the analysis population. These details matter because different choices can affect both the estimate and its uncertainty.

General statistical considerations include checking whether the selected model suits the outcome and whether its assumptions are reasonable. Because the outcome is a bounded score, possible departures from a normal model may be relevant to an analysis, but the registry does not report diagnostic checks or a specific modeling approach. No alternate outcome analysis is posted, so robustness to different reasonable analysis choices cannot be assessed from this record alone.

10. Confidence Intervals and Precision

The estimated mean difference is -4.1 STAI points for VR versus control. Its 95% confidence interval extends from -8.828 to 0.628. The point estimate is negative, but the interval crosses zero: the posted result is compatible with a lower mean in the VR group, little or no mean difference, or a higher mean in the VR group. The interval describes uncertainty in the estimated group contrast, not the range of scores expected for individual participants.

Precision is limited when a confidence interval spans values that imply different conclusions about direction or magnitude. The interval does not identify a single likely value, and its endpoints should not be treated as equally plausible in every sense. They summarize the range generated by the statistical procedure under its assumptions. The registry does not provide enough analysis detail to evaluate those assumptions or to determine whether the interval was adjusted for any factors.

The reported sample sizes are 91 in control and 89 in the VR group. Group standard deviations are 17.11 and 15.22, respectively. These summaries help place the estimate in context, but they do not eliminate uncertainty about the underlying contrast. The record does not report a prespecified precision target or a clinically meaningful difference against which to judge the width of the interval.

Because the interval includes zero, the result does not establish the direction of the underlying mean difference. Because it also spans nonzero values, it does not establish that the groups are equivalent. A conclusion about practical importance would require clinical context and a prespecified meaningful threshold, neither of which is reported in the registry record.

11. Planning a Similar Trial: Sample Size

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

The planning figures are participants per arm, not total events. They are illustrations calculated from the observed effect under the listed assumptions: a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. The effect to detect is set to a stated fraction of the observed effect. The trial’s own original sample-size assumptions and justification are not reported in the registry record.

The row for 100% of the observed effect lists 246 participants per arm for 80% power and 329 participants per arm for 90% power. The row for 75% of the observed effect lists 436 participants per arm for 80% power and 584 participants per arm for 90% power. The row for 50% of the observed effect lists 981 participants per arm for 80% power and 1,313 participants per arm for 90% power.

In plain terms, the 80% power column gives the modeled number of participants per arm for a design with an 80% chance of detecting the specified effect under the planning assumptions, if that effect is the true one. The 90% column uses a higher target chance of detection and therefore gives a larger planning count for each effect scenario. Smaller effects are harder to distinguish from random variation, so the illustrations require more participants per arm as the target effect becomes smaller. Any curve associated with these scenarios represents the relationship between the chosen effect fraction and the resulting planning count, under the same assumptions. These figures are not observed power.

12. How the Sample Size Is Derived

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

Formula

n is the number of participants in each arm, Δ is the difference in means to detect and σ is the common standard deviation.

Worked calculation for this trial

1. Observed difference Δ = -4.100; pooled standard deviation σ = 16.203.
2. n = 2 × (1.96 + 0.842)² × 16.203² / -4.100² = 245.2, rounded up to 246 participants per arm for 80% power.

The smaller-effect rows in the table above repeat the same calculation with the effect multiplied by 0.75 and 0.5 (for ratios, applied to the logarithm of the ratio).

R code

alpha <- 0.05
z_a   <- qnorm(1 - alpha / 2)          # two-sided
delta <- -4.10000000000001                      # observed difference in means
sigma <- 16.2031950310265                     # pooled standard deviation
n_per_arm <- function(power, frac = 1) {
  ceiling(round(2 * (z_a + qnorm(power))^2 * sigma^2 / (delta * frac)^2, 6))
}
for (f in c(1, 0.75, 0.5))
  cat(sprintf("%3.0f%% of observed effect: n per arm = %s (80%% power), %s (90%% power)\n", 100 * f,
              format(n_per_arm(0.80, f), big.mark = ","), format(n_per_arm(0.90, f), big.mark = ",")))

# Check against R's built-in function (t-based, so very slightly larger)
cat("power.t.test:", round(power.t.test(delta = delta, sd = sigma, power = 0.80)$n, 1), "\n")

# Simulation: exact two-sample t-test using simulated means and variances
set.seed(3662607)
n    <- n_per_arm(0.80)
reps <- 20000
m_diff <- rnorm(reps, delta, sigma * sqrt(2 / n))             # difference in sample means
s2     <- sigma^2 * rchisq(reps, 2 * (n - 1)) / (2 * (n - 1))   # pooled sample variance
tstat  <- m_diff / sqrt(s2 * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(tstat) > qt(0.975, 2 * (n - 1))), reps))

Output from running the code

100% of observed effect: n per arm = 246 (80% power), 329 (90% power)
 75% of observed effect: n per arm = 436 (80% power), 584 (90% power)
 50% of observed effect: n per arm = 981 (80% power), 1,313 (90% power)
power.t.test: 246.1 
Simulated power at n = 246 per arm: 0.797 (20000 replicates)

The simulation draws many sets of group means and variances at the planned sample size and counts how often the two-sample t-test rejects the null. It should land close to the target power; at very small required sample sizes it can fall below it, because the normal approximation is rough there.

13. Multiplicity, Missing Data and Analysis Populations

Multiplicity arises when a study tests more than one outcome, contrast, subgroup, or analysis and then considers the collection of results. Repeated testing can increase the chance of obtaining at least one seemingly notable result by chance. The registry lists one primary outcome measure and no secondary outcome measures. It does not provide a broader inventory of planned comparisons or analyses, so the extent of any multiplicity beyond the posted primary result is not reported in the registry record.

The reported p-value is unadjusted. The record does not state whether a multiplicity adjustment was planned, whether the primary outcome was the only inferential test, or whether other analyses were conducted outside the registry. No registry analysis entry is posted. Therefore, the posted result should not be interpreted as resolving how a broader family of outcomes or comparisons was handled.

The registry also does not report how missing outcome observations were handled, the number of participants with available primary outcome data, or the analysis population. It is not possible from the posted record to determine whether the analysis included all randomized participants, only those with observed outcomes, or another defined group. Nor does the record describe imputation, sensitivity analyses, or how participants who did not receive their assigned approach were handled.

These omissions matter because exclusions and missing-data assumptions can affect estimates and uncertainty, particularly when missingness differs between groups or relates to participants’ outcomes. This is a general statistical concern, not evidence that such problems occurred in this trial. The available record reports arm sizes and the outcome comparison but does not provide enough detail to assess the consequences of missing data or to reconstruct the analysis population.

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 registry reports zero serious adverse events among 91 control participants at risk and zero among 89 treatment participants at risk. It also reports zero other adverse events among 91 control participants at risk and zero among 89 treatment participants at risk. Deaths are reported as zero in each group. No serious adverse event terms are listed.

These counts are the adverse-event figures posted in the registry record. A count of zero means that no events in that category are reported for the corresponding group; it is not proof that no event occurred outside the information captured in the record. The registry does not describe event definitions, the period of safety follow-up, how events were collected or attributed, or whether all enrolled participants contributed to every safety count.

Safety counts should be read separately from the anxiety outcome. They do not measure anxiety, and they do not provide information about the size or precision of the primary outcome contrast. The posted figures are limited to the categories and participant counts recorded; they do not support conclusions about unreported safety outcomes or other populations.

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

The posted results describe a randomized comparison of standard pre-procedural education plus virtual reality with standard education alone. For the primary STAI outcome, the reported group means are 65.71 for the VR group and 69.81 for control. The estimated difference is -4.1, with a 95% confidence interval from -8.828 to 0.628. This describes a lower point estimate in the VR group, while leaving uncertainty about the direction and size of the underlying difference.

The confidence interval includes zero, so the result does not establish a difference in either direction. It also does not establish that the two approaches produce equivalent anxiety scores. A finding of equivalence would require a prespecified equivalence margin and a suitable analysis; neither is reported in the registry record. The clinical importance of the estimate also cannot be determined without a meaningful STAI threshold or other relevant context, which is not reported.

The result is about the recorded anxiety outcome in this trial, not every aspect of the catheterization experience. The registry describes the intervention as a 3-D simulation of certain aspects of the upcoming procedure, but the posted primary result does not show which elements of the experience might account for the group comparison. The outcome does not establish effects on other outcomes, since no secondary measure is posted.

The completed status and enrollment of 180 participants provide trial context, but they do not answer questions about missing outcome data, adherence, or generalizability. Those details are not reported in the registry record. The absence of posted adverse events is likewise limited to the listed categories and record. The result should be read as an estimate with substantial uncertainty in its direction and magnitude, rather than as a definitive answer about the effect of virtual reality education in all clinical settings.

16. Why This Trial Matters Statistically

This trial illustrates why an estimated effect should be read together with its uncertainty. The point estimate is negative, but its confidence interval includes zero and extends to values on both sides of no difference. A reader who focuses only on the point estimate may overlook how uncertain the direction and magnitude remain. A reader who focuses only on a p-value may miss the range of effects compatible with the interval.

The outcome is a self-reported anxiety score measured in relation to a procedure. This makes the endpoint a continuous measure rather than a simple event count. Means summarize the groups but can conceal variation among individual participants; the reported standard deviations provide some context about that variation. The registry does not offer individual-level distributions or additional summaries that would show how scores were spread across participants.

The record also demonstrates the value of transparent methods reporting. It specifies the intervention, comparator, primary outcome, and time frame, but does not report the analysis population, missing-data handling, or full statistical plan. Without those details, readers cannot fully assess how the estimate was produced or how sensitive it may be to analytic choices. This is a limitation of what can be concluded from the registry record, not evidence that a particular method was or was not used.

Finally, the sample-size illustrations are planning scenarios based on the observed effect, not a record of the trial’s original design assumptions. They show how planning requirements change when the target effect is smaller or the desired power is higher. This distinction helps prevent retrospective planning calculations from being mistaken for a description of the original trial design.

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 leaves important trial and analysis details unspecified. It does not report the original sample-size justification, the methods for generating or concealing the random allocation sequence, or a full statistical analysis plan. Although masking is listed as none, the record does not further describe which people involved in the trial knew group assignments.

The primary outcome is described as change from baseline to procedure day, but the posted summary does not give the baseline and procedure-day values separately or explain the precise calculation of change. It also does not report the number with available outcome data, the handling of missing observations, or the defined analysis population. These omissions limit assessment of whether the group summaries represent all randomized participants and whether missingness could have influenced the comparison.

No secondary outcome measure or registry analysis entry is posted. The record therefore does not offer additional outcome results or analysis details to assess alongside the primary comparison. It does not report a clinically important STAI threshold, so the practical importance of the estimate cannot be judged from the score difference alone. The record also does not give detailed event definitions or safety follow-up methods for the posted adverse-event counts.

These limitations concern the information available in the registry record. They do not establish that particular procedures were absent or that the reported outcome is invalid. They do mean that independent readers cannot fully reconstruct the analysis or judge the sensitivity of the result to unreported choices.

18. Related Tutorials

19. Related Statistical Calculators

20. Sources

• ClinicalTrials.gov: Impact of Virtual Reality on Pre-procedural anxieTy Prior to Heart cathEterIzAtion - VR-THEIA — NCT03662607.
• Registry record last updated 2026-04-14; status last verified 2026-04.
• Results first posted 2025-03-11.
• 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

VR-THEIA is listed as a completed, randomized, unmasked, parallel-group trial sponsored by Corewell Health West. Enrollment was 180. The trial compared standard pre-procedural education plus a virtual reality experience with standard education alone before cardiac catheterization.

The primary outcome is change in anxiety measured by the STAI from baseline visit to procedure day. The posted group means are 69.81 for control and 65.71 for the VR group. The estimated mean difference for VR versus control is -4.1, with a 95% confidence interval from -8.828 to 0.628 and an unadjusted p-value of 0.089.

The registry lists one primary outcome measure, no secondary outcome measures, and no analysis entry. It reports zero serious adverse events, zero other adverse events, and zero deaths in each group. Details about the original sample-size justification, missing-data handling, analysis population, and full statistical plan are not reported in the registry record.