Virtual Reality Guided Acupuncture Imagery Treatment for Chronic Low Back Pain: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Virtual Reality Guided Acupuncture Imagery Treatment for Chronic Low Back Pain (NCT06814470), a randomized na study. The primary outcome is Retention.

2. Clinical Question

The registry describes a randomized, double-masked, parallel-group study with enrollment of 31. The reported retention counts were 14 of 15 in the VRGAIT group and 14 of 16 in the control group. The posted risk difference is 0.058, with a confidence interval that includes values below and above no difference. These data describe completion in this study; they do not establish that either treatment changes pain or other health outcomes.

3. Trial Design

The registry record identifies this as a completed, randomized, double-masked, parallel-group feasibility study. It lists chronic low-back pain as the condition and Massachusetts General Hospital as the sponsor. Enrollment was 31. The record gives a start date of 2024-07-16 and a primary completion date of 2025-01-03.

Participants were assigned to VRGAIT or a group labeled VRGAIT Control. The registry lists both interventions as “OTHER.” The arm descriptions do not add detail about the treatment procedures, the control experience, or how masking was maintained. Those features are not reported in the registry record, and the arm names alone are not enough to determine them. The phase is listed as NA.

The primary endpoint was retention through the study intervention, described as an average of about four weeks. Retention meant completing all assessments among those enrolled. The registry also lists PROMIS-29, Pain Bothersomeness Scale, MGH Acupuncture Sensation Scale (MASS), and Vividness Scale as secondary outcomes. Numerical arm summaries are posted for MASS and Vividness Scale; numerical summaries for PROMIS-29 and Pain Bothersomeness Scale are not reported in the registry record.

The record lists seven outcome measures and no reported analyses. It does not report the original sample-size justification, a prespecified statistical analysis plan, interim analyses, or details of the analysis population. Randomization and masking are design features, but their presence does not by itself specify how outcomes were analyzed or how missing observations were handled.

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

Reasons for not completing this period:

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: Individuals with chronic low back pain

6. Primary Endpoint

The registry lists the primary outcome as Retention, measured over Through study intervention, an average of about four weeks.

Retention is the primary endpoint. The registry defines it as the proportion of enrolled participants who complete all assessments, with the observation period described as through the study intervention, an average of about four weeks. The posted results express this endpoint as participant counts: 14 of 15 in VRGAIT and 14 of 16 in VRGAIT Control.

Retention is commonly used in feasibility work because it describes whether participants remain engaged through the planned assessment period. Completion can inform whether study procedures and follow-up are workable enough to study further. It is distinct from an efficacy endpoint: completing assessments does not indicate whether pain, function, or another health outcome improved.

The posted unadjusted risk difference is 0.058 for VRGAIT compared with control. Its confidence interval extends from -0.147 to 0.264, and the unadjusted p-value is 0.583. These estimates describe the observed retention contrast and its uncertainty; the interval is compatible with differences in either direction. The registry record does not report a separate adjusted analysis or a statistical analysis plan for retention.

Using all enrolled participants as the denominator is part of the registry’s stated endpoint definition. The record does not provide enough detail to determine whether all analyses followed a particular named analysis population or how any incomplete observations were classified beyond the retention definition.

7. Results Posted in the Registry

• Virtual Reality - Guided Acupuncture Imagery Treatment (VRGAIT): 93.3% (14/15) versus 87.5% (14/16) on control; risk difference 5.8 percentage points (95% CI -14.7 to 26.4), risk ratio 1.07 (0.85–1.34); unadjusted two-proportion z-test p = 0.583.

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.

MGH Acupuncture Sensation Scale (MASS)

• 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:
  • Virtual Reality - Guided Acupuncture Imagery Treatment (VRGAIT): mean 9.00 versus 4.50 on control; difference 4.50 (95% CI -1.43 to 10.43), standardized effect d = 0.56; z-test p = 0.137.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Virtual Reality - Guided Acupuncture Imagery Treatment (VRGAIT) and the control. The interval gives the range of effects that remain compatible with the data.

Vividness Scale

• 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:
  • Virtual Reality - Guided Acupuncture Imagery Treatment (VRGAIT): mean 8.60 versus 7.90 on control; difference 0.70 (95% CI -0.67 to 2.07), standardized effect d = 0.38; z-test p = 0.318.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Virtual Reality - Guided Acupuncture Imagery Treatment (VRGAIT) and the control. The interval gives the range of effects that remain compatible with the data.

The posted secondary results have a broadly similar directional pattern: the VRGAIT group mean is higher than the control group mean on both MASS and Vividness Scale. The uncertainty is also substantial for both comparisons, and their confidence intervals include zero. These measures capture different aspects of participants’ reports and should not be treated as interchangeable evidence or as direct confirmation of the retention result.

The registry also lists PROMIS-29 and Pain Bothersomeness Scale among its secondary outcomes. Numerical arm summaries and comparisons for those measures are not reported in the registry record. The record identifies seven outcome measures overall, but does not provide a complete set of numerical secondary results in the posted material. This limits assessment of whether the observed pattern was consistent across all intended outcomes.

The primary endpoint asks whether participants completed assessments, while secondary scales concern participant-reported outcomes. Their relationship is therefore indirect: good retention can make outcome assessment feasible, but retention does not establish changes in symptoms or perceptions. Conversely, secondary scores do not explain why participants completed or did not complete assessments.

Secondary findings carry less weight as confirmatory evidence because the registry record does not report a detailed analysis plan, does not identify which comparisons were prespecified, and does not report a method for accounting for multiple outcomes or tests. Unadjusted results may be useful for describing patterns and informing further research, but individual p-values should not be treated as definitive evidence. The estimates, their wide intervals, the limited posted results, and the feasibility purpose all matter when interpreting the secondary outcomes.

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

• PROMIS-29
• Pain Bothersomeness Scale
• MGH Acupuncture Sensation Scale (MASS)
• Vividness Scale

9. Statistical Interpretation

10. Statistical Methods Explained

What does the risk difference describe?

The risk difference subtracts the control group’s event proportion from the intervention group’s event proportion. For retention, the event is completing all assessments. A value above zero therefore means the posted completion proportion is higher in VRGAIT than in the control group; a value below zero means it is lower. The reported value is 0.058. This is an unadjusted contrast based on the registry’s posted counts and does not account for other participant characteristics.

General: a risk difference is expressed on the same proportion scale as the event. It can be easier to interpret as an absolute contrast than a relative measure, but it can be imprecise when the number of observations is limited or when event proportions are near the boundaries of the scale.

How should the confidence interval be read?

The retention confidence interval runs from -0.147 to 0.264. It describes a range of values compatible with the data under the calculation’s assumptions. Because it includes zero, the data do not distinguish a positive contrast from no contrast or a negative contrast at the interval’s stated confidence level. The interval is not a guarantee that the true value lies within its endpoints, and it does not assign probability to any one value after the data have been observed.

The record also posts a relative risk of 1.067, with a confidence interval from 0.848 to 1.342, and an odds ratio of 2.0, with a confidence interval from 0.162 to 24.66. These are alternative ways of expressing the same binary retention comparison. The relative risk compares the event proportions as a ratio; the odds ratio compares event odds. Their intervals are broad and include the value representing no relative difference. Risk differences, relative risks, and odds ratios use different scales, so their numerical values should not be compared as though they were interchangeable.

What does the unadjusted p-value tell us?

The primary comparison has an unadjusted p-value of 0.583. In general, a p-value measures how incompatible the observed data are with a specified no-difference model, given the test assumptions. It is not the probability that the null hypothesis is true, and it does not measure the size or practical importance of a difference. A value such as this does not demonstrate equivalence; demonstrating equivalence would require an appropriate design and prespecified margin, neither of which is reported in the registry record.

The secondary comparisons also have unadjusted p-values. MASS has a posted mean difference of 4.5, a confidence interval from -1.428 to 10.43, and an unadjusted p-value of 0.137. Vividness Scale has a posted mean difference of 0.7, a confidence interval from -0.675 to 2.075, and an unadjusted p-value of 0.318. These estimates are based on posted group means and standard deviations. Neither interval excludes zero. No adjusted analyses are reported in the registry record.

How are continuous outcomes summarized?

For MASS and Vividness Scale, the registry reports group means and standard deviations. A mean describes the average score in a group, while a standard deviation describes how dispersed individual scores are around that mean. The mean difference compares the group means. General: a standard deviation reflects variation among observations, whereas the standard error reflects uncertainty in an estimated mean. Neither by itself tells whether a scale difference matters to participants; the registry record does not report a threshold for clinical importance.

The posted standardized effect-size values are 0.562 for MASS and 0.377 for Vividness Scale. A standardized effect expresses a mean contrast relative to a measure of spread, putting it on a scale independent of the original units. It does not remove uncertainty or establish that an observed difference is clinically meaningful. The registry lists no reported analyses for these secondary outcomes.

Why do analysis details matter?

Randomization can support a fair comparison when allocation and follow-up are implemented as planned, but interpretation also depends on analysis choices. The registry record does not report an analysis plan, an adjusted model, missing-data methods, or the population used for analyses beyond the retention endpoint definition. It therefore is not possible to establish from the record whether the secondary comparisons were prespecified, how incomplete secondary measurements were treated, or whether any covariate adjustment was intended.

General: adjustment for multiple comparisons matters when many outcomes or tests are examined, because the chance of at least one apparently notable result can rise as the number of tests increases. The record lists multiple outcomes and gives no multiplicity procedure. The unadjusted secondary p-values should consequently be interpreted cautiously, alongside the estimates and their confidence intervals, rather than as stand-alone confirmatory findings.

11. Confidence Intervals and Precision

Precision concerns how narrowly the data locate an estimated effect. The retention risk difference is 0.058, with a confidence interval from -0.147 to 0.264. The interval spans zero and values on both sides of zero, so the point estimate alone gives an incomplete picture. The observed counts are close, but the uncertainty around the contrast is substantial relative to the scale of the estimate.

The relative-risk interval, 0.848 to 1.342, and odds-ratio interval, 0.162 to 24.66, also indicate considerable uncertainty. The confidence intervals include the respective no-difference values and allow a broad range of contrasts. Different effect measures have different null values and scales; the risk difference’s null is zero, while the relative risk and odds ratio use one.

The continuous secondary estimates are also imprecise. For MASS, the mean difference is 4.5 with a confidence interval from -1.428 to 10.43. For Vividness Scale, the mean difference is 0.7 with a confidence interval from -0.675 to 2.075. Both intervals include zero. These ranges do not establish that the true group means are equal; they show that the posted data do not locate the contrasts precisely enough to exclude zero under the reported calculations.

Confidence intervals are especially useful alongside point estimates in a feasibility study: they reveal the range of effects still compatible with the data. They do not resolve whether an effect would be important in practice. The registry record does not report thresholds for meaningful differences on the secondary scales or a target precision for retention. As a result, the estimates can be described statistically, but their clinical importance cannot be determined from the posted record alone.

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 illustrations translate the observed contrasts into planning quantities under stated assumptions. For the binary retention comparison, the figures are participants per arm. The same is true for the continuous secondary-outcome planning illustrations; none of these entries is a total number of events. The calculation assumptions are a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. Each planning scenario uses the stated fraction of the observed effect as the effect to detect.

For retention, planning for 100% of the observed effect gives 399 participants per arm for 80% power and 534 participants per arm for 90% power. Planning for 75% of the observed effect gives 758 participants per arm for 80% power and 1,014 participants per arm for 90% power. Planning for 50% of the observed effect gives 1,812 participants per arm for 80% power and 2,425 participants per arm for 90% power. The corresponding illustrations for MASS and Vividness Scale apply the same assumptions to their own observed effects.

In plain terms, the 80% power column gives the modeled number per arm for an 80% chance of detecting the specified effect under the calculation assumptions; the 90% power column gives the modeled number per arm for a 90% chance. Smaller effects are harder to distinguish from random variation, so planning to detect a smaller fraction of the observed effect requires more participants. The curve should be read as illustrating that relationship, not as a forecast of the results of a future study. These are planning illustrations, not observed power; the original trial’s design assumptions are not reported in the registry record.

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 = 0.875; treatment proportion p₁ = 0.933; average p̄ = 0.904.
2. First term: z_1−α/2 × √[2p̄(1−p̄)] = 1.96 × 0.4163 = 0.8159.
3. Second term: z_1−β × √[p₀(1−p₀) + p₁(1−p₁)] = 0.842 × 0.4142 = 0.3486.
4. n = (0.8159 + 0.3486)² / (0.0583)² = 398.6, rounded up to 399 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 <- 0.875                          # control proportion
p1 <- 0.933333333333333                          # 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(6814470)
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 = 399 (80% power), 534 (90% power)
 75% of observed effect: n per arm = 758 (80% power), 1,014 (90% power)
 50% of observed effect: n per arm = 1,812 (80% power), 2,425 (90% power)
power.prop.test: 398.6 
Simulated power at n = 399 per arm: 0.806 (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, a multiplicity procedure, or which secondary comparisons were designated as confirmatory. It lists multiple outcomes and provides unadjusted comparisons for the primary endpoint and posted secondary measures. When many outcomes or tests are examined, unadjusted p-values do not account for the increased opportunity to find an apparently notable result by chance. Without a reported plan, the secondary p-values are best read as descriptive rather than as a controlled family of confirmatory tests.

Methods for handling missing data are not reported in the registry record. Retention itself is defined by completing all assessments among enrolled participants, and the posted counts describe completion for that endpoint. The record does not explain how incomplete or unavailable values for secondary scales were handled, whether any imputation was used, or whether analyses used only observed measurements.

The analysis population is also not specified beyond the stated retention definition. The record does not say whether the analyses followed an intention-to-treat, per-protocol, or other named approach. Random assignment is reported, but the analysis population and the way participants are handled after randomization are separate methodological questions.

These omissions matter because different analysis choices can affect estimates and uncertainty, particularly when outcomes are missing or multiple comparisons are considered. The registry lists seven outcome measures and no reported analyses, while arm summaries and comparisons are posted for the primary endpoint and two secondary measures. The record does not explain the relationship between the listed outcome measures and the absence of reported analyses. Readers should therefore distinguish the numerical results that are posted from analysis procedures that are not documented.

15. 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 events in the VRGAIT group among 15 participants at risk and zero in the control group among 16 participants at risk. The registry also reports zero other adverse events in each group, and deaths are recorded as zero in both groups. These are counts as recorded in the registry, not estimates that the risk of an adverse event is zero.

For a small feasibility study, an absence of reported events during the observation period is limited information about safety. It cannot rule out uncommon events or events not captured or reported in the record. The registry does not list serious adverse event terms, and no further detail on event definitions, collection procedures, or duration of safety monitoring is reported. The figures should be read as the recorded results for this study, not as a general safety conclusion about either intervention.

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

The posted primary result describes assessment completion in two randomized groups. The observed counts were 14 of 15 for VRGAIT and 14 of 16 for VRGAIT Control, with a risk difference of 0.058. The confidence interval, -0.147 to 0.264, is compatible with a range of contrasts that includes no difference. This is a finding about retention during the study intervention, not evidence that either group experienced a change in chronic low-back pain.

The secondary outcomes provide limited descriptive information. The posted group means are higher for VRGAIT on MASS and Vividness Scale, but the unadjusted confidence intervals for their mean differences include zero. Numerical findings for PROMIS-29 and Pain Bothersomeness Scale are not reported in the registry record. These results do not establish a clinical benefit or a lack of benefit, and the record does not provide thresholds to interpret the practical importance of the scale differences.

The study is identified as a feasibility study, and its primary endpoint is completion. Its results can describe how many participants completed assessments in the study and the uncertainty around the difference between groups. They cannot establish equivalence, determine treatment efficacy, or characterize safety beyond the recorded adverse-event counts. Those conclusions would require information and analyses not reported in the registry record.

The planning illustrations should be interpreted separately from observed outcomes. They show how participant requirements vary under specified assumptions and effects based on posted estimates; they do not show that the trial had adequate or inadequate power under its original design. The original sample-size justification and design assumptions are not reported in the registry record.

17. Why This Trial Matters Statistically

This study is statistically informative because it separates a feasibility question from a clinical-effect question. Retention is directly relevant to whether participants complete assessments over the intervention period. The endpoint has an explicit definition and posted arm counts, so the result can be interpreted as a completion outcome rather than being mistaken for symptom improvement.

The report also illustrates why effect estimates need to be read with uncertainty. The risk-difference point estimate favors VRGAIT, but its confidence interval includes effects in either direction. The same principle applies to the continuous secondary outcomes: their point estimates do not by themselves describe how precisely the contrasts are known. Focusing only on the direction of a point estimate or on an unadjusted p-value would omit important information.

There is also a useful distinction between observed results and planning calculations. The sample-size illustrations show how assumptions about the effect to detect and desired power lead to different planning requirements. They are not retrospective evidence about whether the completed study had a particular chance of success, and the record does not document the original design assumptions.

Finally, the record makes visible the limits of registry reporting. It provides a randomized, double-masked design description and numerical results for selected outcomes, but does not report the statistical analysis plan, missing-data methods, analysis population, or multiplicity approach. Those details are essential to a fuller appraisal of how estimates were produced and how strongly secondary findings can be interpreted. Clear distinctions between reported results and unreported methods help keep conclusions proportionate to the evidence.

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 enrollment and arm sizes were modest, and the confidence intervals are broad. That limits the precision of the retention and secondary-outcome comparisons. The posted estimates can therefore accommodate materially different underlying contrasts, including values on both sides of no difference. The point estimates should not be treated as precise descriptions of effects beyond this study.

The registry record gives limited detail about the intervention and control conditions. It does not explain the specific treatment procedures, the control experience, or the implementation of double masking. Without those descriptions, the study conditions cannot be fully characterized from the record.

Although the record lists seven outcome measures, complete numerical results are not posted for all listed secondary outcomes. PROMIS-29 and Pain Bothersomeness Scale are named but their numerical results are not reported in the registry record. The record also lists no reported analyses and does not document a statistical analysis plan, adjustment for multiple comparisons, missing-data handling, or analysis population.

The primary endpoint is retention rather than a clinical measure of low-back pain. It answers a feasibility question about assessment completion and should not be interpreted as an estimate of symptom change. The record does not report thresholds for clinically meaningful differences on the secondary measures, further limiting conclusions about the practical importance of their estimated contrasts.

Finally, the sample-size illustrations use observed effects and stated planning assumptions, while the original design assumptions are not reported. They cannot establish whether the study was planned around a particular target effect or precision. These limitations make the posted findings useful for describing the record, but not sufficient for strong claims about clinical outcomes or generalizability.

19. Related Tutorials

20. Related Statistical Calculators

21. Sources

• ClinicalTrials.gov: Virtual Reality Guided Acupuncture Imagery Treatment for Chronic Low Back Pain — NCT06814470.
• Registry record last updated 2026-01-26; status last verified 2024-11.
• Results first posted 2026-01-26.
• 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

NCT06814470 is a completed, randomized, double-masked, parallel-group feasibility study of virtual reality-guided acupuncture imagery treatment for chronic low-back pain, sponsored by Massachusetts General Hospital. The registry reports enrollment of 31 and identifies retention through the intervention period, averaging about four weeks, as the primary endpoint.

Retention counts were 14 of 15 in the VRGAIT arm and 14 of 16 in the control arm. The posted risk difference is 0.058, with a confidence interval from -0.147 to 0.264. Numerical secondary results are posted for MASS and Vividness Scale, while numerical results for PROMIS-29 and Pain Bothersomeness Scale are not reported in the registry record. The record reports zero serious adverse events, zero other adverse events, and zero deaths in each group.

Interpretation is limited by uncertainty in the estimates and by unreported analysis details, including the statistical plan, multiplicity approach, missing-data methods, and analysis population. The posted findings describe feasibility and recorded outcomes; they do not establish clinical efficacy.