A Pilot Study of Acupuncture Treatment for Dysphagia: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for A Pilot Study of Acupuncture Treatment for Dysphagia (NCT00797732), a randomized na study. The primary outcome is Outcome Compliance Rate.

2. Clinical Question

3. Trial Design

This was a randomized, double-masked, parallel-group pilot study registered as NCT00797732. Its official title describes a pilot randomized controlled trial of acupuncture for dysphagia after chemoradiation therapy in head and neck cancer patients. The record lists the phase as NA and the study status as completed.

The trial enrolled 42 participants. The active acupuncture and sham acupuncture arms each had 21 participants. Allocation is listed as randomized, masking as double, and the model as parallel. The registry record does not identify which people were masked or describe how masking was maintained, so those details are not reported in the registry record.

The study's stated purpose was to evaluate the feasibility of conducting a randomized sham-controlled trial and to collect preliminary safety and efficacy data on acupuncture. The primary outcome, however, was assessment compliance at baseline and 6 months post acupuncture treatment. This makes the primary endpoint relevant to feasibility and follow-up completion; it is not itself a measure of the treatment's effect on dysphagia.

The record lists Dana-Farber Cancer Institute as the sponsor, a start date of 2008-12, and primary completion in 2013-01. The intervention descriptions provide some information about active and sham needling, but both descriptions are incomplete in the registry record. The protocol's full treatment schedule, the details of the double-masking procedures, and the trial's original sample-size justification 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.

Before assignment: Since one primary aim was to assess feasibility as measured by recruitment the screening non-randomized count is included in the participant flow.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: The analysis population is comprised of all randomized participants.

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: The analysis population is comprised of all randomized participants.

6. Primary Endpoint

The registry lists the primary outcome as Outcome Compliance Rate, measured over Assessed at baseline and at 6 months post acupuncture treatment.

The primary endpoint, called Outcome Compliance Rate, is the percentage of enrolled participants who completed the primary study assessments at baseline and in long-term follow-up 6 months post acupuncture treatment. The listed analysis population comprises all randomized participants. The posted outcome reports 76.2% for active acupuncture, with a 95% confidence interval from 52.8% to 91.8%, and 85.7% for sham acupuncture, with a 95% confidence interval from 63.6% to 97.0%.

Completion is useful in a pilot trial because it describes whether participants contribute the assessments needed for follow-up. In general, a completion endpoint can inform the practical feasibility of collecting outcome data, but it does not establish whether the treatment changes the clinical condition. Here, the primary endpoint concerns completing assessments rather than the severity of swallowing difficulty.

The registry record also lists two secondary outcome descriptions related to MDADI scores, including change from baseline to 12 months post chemoradiation therapy. Results for those secondary outcomes are not reported in the registry record. The relationship between the listed 6-month post-acupuncture compliance assessment and any other follow-up schedule beyond the information in the outcome description is not reported in the registry record.

7. Results Posted in the Registry

• Active Acupuncture: 76.2% (16/21) versus 85.7% (18/21) on control; risk difference -9.5 percentage points (95% CI -33.1 to 14.1), risk ratio 0.89 (0.66–1.20); unadjusted two-proportion z-test p = 0.432.

8. Statistical Interpretation

9. Statistical Methods Explained

The primary outcome is binary at the participant level: each randomized participant either completed the defined assessments or did not. The registry reports the percentage completing those assessments in each arm and a 95% confidence interval for each percentage. The posted counts are 16 of 21 in the active arm and 18 of 21 in the sham arm. This presentation is appropriate for a proportion outcome because it expresses completion relative to the number of participants in each group.

What does a confidence interval describe?

In general, a confidence interval describes the uncertainty around an estimate under the statistical procedure used to construct it. It is not a range that identifies the exact value for an individual participant, and it is not a guarantee that the underlying rate lies within the displayed endpoints. Wider intervals indicate less precision. The active-arm interval is 52.8% to 91.8%, and the sham-arm interval is 63.6% to 97.0%. Both intervals cover a broad range of possible completion rates, so the point estimates should not be read as precise descriptions of the rates that would necessarily be seen in a larger group.

How should the arm comparison be read?

The posted comparison is a risk difference, comparing the active arm with the sham arm. In general, a risk difference expresses the difference between two proportions on the proportion scale; its direction depends on the order of the groups. The observed percentages are lower in the active arm than in the sham arm. The registry also reports a risk ratio and an odds ratio, which express comparisons on different scales. These measures do not replace the arm-specific percentages, and their interpretation depends on the outcome definition and group ordering. The posted unadjusted p value is 0.432. The specific statistical test used to obtain it is not reported in the registry record.

In general, a p value describes how compatible the observed data are with a specified null model, conditional on the assumptions of the test. It is not the probability that the null hypothesis is true, and it does not measure the size or clinical importance of a difference. A p value such as the one should be considered alongside the estimates and confidence intervals, rather than used alone to classify the result as positive or negative.

What does randomization contribute?

In general, random allocation is intended to create groups that are comparable on average with respect to factors known and unknown at the time of assignment. It supports an arm comparison but cannot ensure that small groups will be balanced on every characteristic. The record states that the analysis population comprised all randomized participants. The detailed analysis procedures, including whether any covariate adjustment was planned or used, are not reported in the registry record.

What does double masking mean in this record?

The registry labels the study double-masked. In general, masking is used to reduce the chance that knowledge of assigned treatment influences participant experiences, assessment, or other study procedures. The record does not state which roles were masked, whether masking was assessed, or how the sham procedure was designed to preserve masking beyond the description of its intended similarity to active acupuncture. Those procedural details are not reported in the registry record.

Why distinguish feasibility from clinical efficacy?

In general, a feasibility outcome evaluates whether a study procedure, such as participant follow-up, can be carried out and measured. Completion of assessments speaks to data collection. It is not interchangeable with a clinical endpoint measuring dysphagia or swallowing function. The registry identifies the study as a pilot and gives preliminary safety and efficacy as broader aims, but the posted primary outcome is assessment compliance. A clinical interpretation of the primary result should therefore remain limited to completion.

The registry lists four outcome measures and one analysis. It identifies two secondary outcome descriptions related to MDADI scores, but their numerical results and analysis details are not reported in the registry record. No adjustment for multiple outcomes or subgroup analyses is described. The analysis plan, handling of incomplete observations, and rationale for the confidence-interval method are also not reported in the registry record. General statistical interpretation can explain the meaning of proportions, comparisons, p values, and intervals, but it cannot identify unreported design or analysis choices.

10. Confidence Intervals and Precision

The arm-specific confidence intervals for the primary outcome are broad. For active acupuncture, the reported completion rate is 76.2%, with a 95% confidence interval from 52.8% to 91.8%. For sham acupuncture, the rate is 85.7%, with a 95% confidence interval from 63.6% to 97.0%. These intervals overlap. Their width indicates that the estimated rates are not highly precise, which is important when interpreting the point estimates.

In general, confidence intervals reflect sampling uncertainty under the method used to calculate them. With a limited number of participants, each participant's outcome can have a substantial influence on the group proportion. The intervals do not account automatically for every possible source of uncertainty, such as measurement or design limitations. The method used to construct these intervals is not reported in the registry record.

The posted arm comparison also has a confidence interval for the risk difference, but the principal numerical comparison reported alongside the primary result is the unadjusted p value of 0.432. The p value alone does not communicate precision or the range of effect sizes compatible with the data; the comparison interval is the relevant measure for that purpose. The interval spans values on both sides of no difference, which is consistent with uncertainty about the direction and size of the underlying contrast.

These intervals should not be interpreted as proving that the arms have the same completion rate. Nor do they establish a meaningful difference. They show that the observed percentages are estimates with considerable uncertainty in this pilot sample. More precise estimation would generally require more information, but the appropriate target depends on the study question and design.

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 calculations are planning illustrations based on the observed effect, not the trial's original design assumptions. The figures are participants per arm, not total events. They use a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. The effect to detect is set to the stated fraction of the observed effect. The original trial's sample-size justification and design assumptions are not reported in the registry record.

The 80% power column gives the illustrated number of participants per arm for a design intended to have an 80% chance of detecting the specified effect under the planning assumptions, if that effect and the other assumptions hold. The 90% power column gives the corresponding number for a 90% chance. These are planning quantities, not descriptions of the probability that this completed trial detected an effect.

The rows consider planning for 100% of the observed effect, 75% of the observed effect, and 50% of the observed effect. For 100% of the observed effect, the illustration gives 266 participants per arm for 80% power and 356 participants per arm for 90% power. For 75% of the observed effect, it gives 451 and 603 participants per arm, respectively. For 50% of the observed effect, it gives 961 and 1,286 participants per arm, respectively. Smaller effects need more participants to detect under otherwise unchanged assumptions.

The figures are sensitive to the observed effect used as their starting point. Since that effect comes from a small pilot, it is uncertain and may not represent the effect in a future study. The calculations are not observed power. They are conditional planning illustrations and should not be read as evidence that a future study with the listed size would necessarily produce a particular result. The accompanying curve should be read as another display of these planning relationships, rather than as additional trial observations.

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 = 0.857; treatment proportion p₁ = 0.762; average p̄ = 0.810.
2. First term: z_1−α/2 × √[2p̄(1−p̄)] = 1.96 × 0.5553 = 1.0884.
3. Second term: z_1−β × √[p₀(1−p₀) + p₁(1−p₁)] = 0.842 × 0.5512 = 0.4639.
4. n = (1.0884 + 0.4639)² / (-0.0952)² = 265.7, rounded up to 266 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 <- 0.857142857142857                          # control proportion
p1 <- 0.761904761904762                          # 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(797732)
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 = 266 (80% power), 356 (90% power)
 75% of observed effect: n per arm = 451 (80% power), 603 (90% power)
 50% of observed effect: n per arm = 961 (80% power), 1,286 (90% power)
power.prop.test: 265.7 
Simulated power at n = 266 per arm: 0.804 (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 lists four outcome measures and reports one analysis. The primary endpoint is outcome compliance, while the two named secondary outcomes concern MDADI scores. Results for those secondary outcomes are not reported in the registry record. It is also not reported whether the study's analysis plan adjusted for multiple outcomes, specified a hierarchy among outcomes, or defined confirmatory versus exploratory comparisons.

In general, examining multiple outcomes or comparisons can increase the chance of observing an apparently notable result by chance. Multiplicity methods are sometimes used to address that issue, but the registry record does not state that any were used. The posted primary comparison has an unadjusted p value of 0.432. No adjustment should be assumed, and no conclusion about multiplicity control can be drawn from the record.

The primary outcome description says that the analysis population comprised all randomized participants. The record does not give further detail on the analysis population for secondary outcomes, on exclusions after randomization, or on how participants with incomplete assessments were handled. Although the endpoint itself concerns assessment completion, the exact rules for determining completion or handling partial assessments are not reported in the registry record.

In general, missing outcome data can affect the interpretation of a comparison when the likelihood of missingness differs between groups or is related to participants' outcomes. The arm-specific completion figures describe the proportion completing the assessments, but they do not reveal why assessments were incomplete or what the unobserved outcomes would have been. Reasons for noncompletion, missing-data assumptions, imputation methods, and sensitivity analyses are not reported in the registry record.

The registry reports one analysis but does not provide a full statistical analysis plan. The test underlying the p value, any adjustment for baseline factors, prespecified subgroup analyses, and the treatment of protocol deviations are not reported in the registry record. These omissions limit the ability to assess how closely the posted analysis followed a prespecified plan or how robust it is to alternative analytic choices.

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.

Most frequent non-serious adverse event terms

The serious adverse event figures show zero participants with a serious adverse event in each arm. Each arm had 21 participants at risk. The registry also reports zero deaths in both arms. For other adverse events, the count is one in the active acupuncture arm and zero in the sham acupuncture arm.

These are counts, not a comprehensive characterization of safety. The record does not identify the term for the one other adverse event, describe its timing or severity, or provide information about whether it was considered related to treatment. The list of top serious adverse event terms is empty.

In general, observing no serious adverse events in a small group does not establish that serious events cannot occur. The number of participants followed and the duration and completeness of safety follow-up affect what can be learned. The safety follow-up details are not reported in the registry record. The counts should therefore be read descriptively and within the limits of the sample, rather than as a definitive estimate of risk.

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

The primary result describes the completion of study assessments in a randomized comparison of active and sham acupuncture. The active arm had a reported completion rate of 76.2%, while the sham arm had a rate of 85.7%. The unadjusted p value was 0.432, and the arm-specific confidence intervals are wide. These data leave substantial uncertainty about the underlying completion rates and the comparison between arms.

The primary outcome does not measure swallowing function, dysphagia severity, or change in MDADI score. The record lists MDADI-related secondary outcomes, but their results are not reported in the registry record. Consequently, the posted primary result cannot be used to conclude that active acupuncture improved or worsened dysphagia relative to sham acupuncture.

The finding also does not establish that the arms are equivalent. A non-significant comparison is not proof of no difference, and the confidence intervals are compatible with a range of possible underlying rates. The data are most directly informative about assessment completion among the randomized participants in this pilot trial.

The safety figures report no serious adverse events and no deaths in either arm, alongside one other adverse event in the active arm and none in the sham arm. These small counts do not resolve the possibility of uncommon events, and details about the one event are not reported in the registry record. The trial was intended to assess feasibility and collect preliminary safety and efficacy data; the posted primary endpoint chiefly informs the feasibility aspect.

16. Why This Trial Matters Statistically

This trial is statistically informative as an example of how a pilot study can have a feasibility-oriented primary endpoint rather than a direct clinical efficacy endpoint. Outcome compliance captures whether participants completed assessments at the planned time points described in the record. That information is distinct from estimating an intervention's effect on dysphagia and should not be substituted for an unreported clinical outcome.

The randomized, sham-controlled comparison and the reported arm-specific proportions make the primary outcome interpretable as a comparison of completion in the two assigned groups. At the same time, 21 participants per arm yields broad confidence intervals. The estimates and their uncertainty are more informative together than the p value alone, which does not quantify the size or precision of a contrast.

The pilot framing matters for planning. The displayed sample-size calculations use fractions of the observed effect to illustrate how planning assumptions affect participant requirements. The original trial's sample-size justification is not reported in the registry record, so these illustrations should not be mistaken for the study's original target or for evidence about its achieved power.

The record also highlights the importance of distinguishing what has been registered as an outcome from what has numerical results posted. MDADI-related secondary outcomes are named, but results are not reported in the registry record. Without those results and further analysis details, readers cannot use them to assess the clinical outcome question. Clear reporting of endpoint definitions, missing-data handling, and analysis methods would support a fuller statistical interpretation.

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.
• Participant counts were reconstructed from posted percentages and arm sizes, so small rounding differences are possible.

The primary endpoint is assessment compliance, not a direct measure of dysphagia. Although the study's stated purpose includes collecting preliminary safety and efficacy data, efficacy results for the listed MDADI outcomes are not reported in the registry record. This limits the clinical scope of interpretation to the primary completion outcome and the safety counts posted.

The trial enrolled 42 participants, with 21 in each arm. The completion estimates therefore have broad confidence intervals, and the comparison is imprecise. The p value and the observed arm percentages should not be treated as definitive evidence for or against a difference. The pilot setting further limits the role of the observed contrast as a reliable planning estimate for a later study.

The registry record contains incomplete intervention descriptions. It describes elements of the active and sham protocols, but the full details are not reported in the registry record. The specific roles masked, procedures for maintaining masking, full outcome assessment rules, and reasons for incomplete assessments are also not reported in the registry record.

The record does not report the original sample-size justification, the test used for the primary comparison, the method used to calculate confidence intervals, or a full statistical analysis plan. It does not describe multiplicity procedures, covariate adjustment, missing-data methods, or sensitivity analyses. These gaps prevent a detailed assessment of prespecification and robustness. Safety interpretation is also limited because the one other adverse event is not described and follow-up details are not reported in the registry record.

18. Related Tutorials

19. Related Statistical Calculators

20. Sources

• ClinicalTrials.gov: A Pilot Study of Acupuncture Treatment for Dysphagia — NCT00797732.
• Registry record last updated 2018-02-13; status last verified 2018-01.
• Results first posted 2018-02-13.
• 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

NCT00797732 is a completed randomized, double-masked, parallel-group pilot study of active versus sham acupuncture for dysphagia after chemoradiation therapy in head and neck cancer patients. The trial enrolled 42 participants, with 21 assigned to each arm. The primary outcome was completion of baseline and long-term follow-up assessments 6 months post acupuncture treatment.

Reported completion was 76.2% with active acupuncture and 85.7% with sham acupuncture. The unadjusted p value was 0.432, and the reported confidence intervals are broad. No serious adverse events or deaths were reported in either group; one other adverse event was reported in the active arm and none in the sham arm. MDADI-related secondary outcomes are listed, but their results are not reported in the registry record. The posted primary result concerns assessment completion and does not establish a treatment effect on dysphagia.