Effect Comparison of Electro-acupuncture and Prucalopride for Severe Chronic Constipation: a Randomized Controlled Trial: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Effect Comparison of Electro-acupuncture and Prucalopride for Severe Chronic Constipation: a Randomized Controlled Trial (NCT02047045), a randomized na study. The primary outcome is the Proportion of Participants With ≥3 Mean Weekly CSBMs Over Weeks 3-8.

2. Clinical Question

3. Trial Design

The registry describes a randomized, single-masked, parallel-group trial conducted at multiple centers. Its official title identifies it as a noninferiority randomized controlled trial. The listed phase is NA. The sponsor was Guang'anmen Hospital of China Academy of Chinese Medical Sciences. The record gives a start date of 2014-04, a primary completion date of 2016-08, and a completed status.

The planned enrollment was 560, with 280 assigned to each group. The record says that 3 participants in the electro-acupuncture group and 2 in the prucalopride group withdrew informed consent and were excluded from baseline analysis. The primary outcome entries use 277 participants for electro-acupuncture and 278 for prucalopride. The registry does not report further detail about the analysis population or the handling of outcomes for participants who withdrew.

The electro-acupuncture schedule was once per day for 30 min, 5 times/week for the first 2 weeks, then 3 times/week for the next 6 weeks. The prucalopride group took 2mg/day orally in the morning before breakfast. The primary timeframe was weeks 3-8, described as the latter 6-week treatment period.

The registry lists 14 outcome measures and 8 secondary outcomes. Secondary measures include proportions reaching specified CSBM thresholds, changes in weekly CSBMs and spontaneous bowel movements, stool consistency and straining scores, time to the first CSBM, and constipation-related quality of life. The listed assessment windows extend beyond treatment, including weeks 11-12, 15-16, 19-20, and 31-32. The registry record does not report fuller details of masking, the randomization procedure, allocation concealment, or the statistical analysis plan.

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.

Baseline

Reasons for not completing this period:

Treatment Period (8 Weeks )

Reasons for not completing this period:

Follow-up Period (24 Weeks)

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: We recruited 560 participants (280 for each group) in total; however, 3 participants from EA group and 2 from prucalopride group withdrew their informed consents. Therefore, they were not included in the baseline analysis.

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: Baseline analysis population was the recruited patients with baseline data. We recruited 560 participants (280 for each group) in total; however, 3 participants from EA group and 2 from prucalopride group withdrew their informed consents with no baseline data. Therefore, they were not included in the baseline analysis.

6. Primary Endpoint

The registry lists the primary outcome as the Proportion of Participants With ≥3 Mean Weekly CSBMs Over Weeks 3-8, measured over over weeks 3-8 (the latter 6-week treatment).

The primary endpoint is the percentage of participants whose mean weekly number of complete spontaneous bowel movements (CSBMs) was at least 3 during weeks 3-8. The endpoint description says each participant's mean weekly CSBMs were calculated over that period, participants meeting the threshold were counted, and the count was divided by the total cases at baseline and multiplied by 100%. The record defines the assessment period as the latter 6 weeks of treatment.

This is a binary responder endpoint: each participant either meets the stated threshold or does not. In general, converting a count-based measure into a responder proportion can make the result easier to interpret as the share of participants reaching a predefined level, while also discarding information about differences within each category. The threshold and observation period specify what counts as a response; they do not describe the full distribution of bowel-movement counts.

The posted proportions are 36.2% for electro-acupuncture and 37.8% for prucalopride. The primary outcome is one part of a broader set of outcomes: the registry also lists changes in weekly CSBMs and other bowel-movement measures, symptom ratings, time to the first CSBM, and quality of life. The registry record does not report the rationale for selecting this endpoint over the other measures or the clinical basis for the threshold.

7. Results Posted in the Registry

• Prucalopride: 37.8% (105/278) versus 36.1% (100/277) on control; risk difference 1.7 percentage points (95% CI -6.4 to 9.7), risk ratio 1.05 (0.84–1.30); unadjusted two-proportion z-test p = 0.684.

8. Statistical Interpretation

9. Statistical Methods Explained

The primary measure is a binary outcome expressed as a percentage: a participant either reached at least 3 mean weekly CSBMs during weeks 3-8 or did not. The registry's endpoint description states that the mean weekly CSBM measure was determined for each participant over the assessment period, then the number meeting the threshold was divided by the total cases at baseline and expressed as a percentage. The posted group proportions are 36.2% and 37.8%.

What does a risk difference describe?

In general, a risk difference compares the proportions with an event in two groups by subtracting one proportion from the other. Its scale is the proportion scale, so values below zero and above zero correspond to effects in opposite directions, depending on which group is subtracted from which. The recalculated risk difference is 0.017, with interval endpoints from -0.064 to 0.097. The registry's comparison identifies prucalopride as the comparison arm and electro-acupuncture as the reference arm. The record does not provide the sponsor's formal analysis or an adjusted estimate.

Other comparative measures can express the same binary outcome on different scales. A risk ratio compares proportions as a ratio, while an odds ratio compares odds. The registry lists recalculated estimates of 1.046 for the risk ratio, with interval endpoints 0.842 and 1.3, and 1.074 for the odds ratio, with interval endpoints 0.761 and 1.517. These measures are not interchangeable in interpretation, and their numerical scales differ. They are unadjusted recalculations from posted summary statistics, not a substitute for an analysis plan or a sponsor analysis.

What does the p-value tell the reader?

In general, a p-value is calculated under a null hypothesis and a statistical model. It describes how often results at least as incompatible with that null would be expected if the model and null were correct. The posted unadjusted p-value is 0.684. A p-value is not the probability that there is no treatment difference, and it does not tell the reader whether a difference is large enough to matter. It also cannot establish noninferiority by itself. For a noninferiority question, the estimate and its uncertainty must be assessed relative to a prespecified margin. That margin and the formal testing procedure are not reported in the registry record.

Why does the interval matter?

In general, a confidence interval communicates the uncertainty around an estimate under the method used to construct it. A narrow interval indicates greater precision than a wide interval on the same scale, while an interval that covers a broad range leaves more possible values compatible with the data and method. The posted interval for the risk difference extends from -0.064 to 0.097. Its endpoints fall on both sides of zero. The confidence level and construction method for this interval are not reported in the registry record, so they should not be inferred from the displayed endpoints.

The registry lists 100 participants meeting the endpoint in the electro-acupuncture group and 105 in the prucalopride group, with denominators of 277 and 278, respectively, in the recalculated comparison. These counts sit alongside the posted percentages, but do not reveal how participants with missing outcome data were handled or whether all assigned participants were included in a formal analysis. The registry notes withdrawals from baseline analysis; a complete flow of participants through the primary outcome analysis is not reported.

How should the design label be interpreted?

The trial is described as randomized, single-masked, parallel-group, and noninferiority in its official title. These labels describe intended design features, not the success of the design or the outcome. In general, random assignment aims to balance measured and unmeasured prognostic factors across groups, while masking can reduce some forms of bias. The registry record does not report who was masked, how randomization was generated, or how allocation was concealed. It also does not report the planned noninferiority margin or a detailed analysis method. Consequently, the design label cannot fill in those missing details.

The outcome is one of 14 measures listed in the registry, and 8 secondary outcomes are listed. In general, evaluating many outcomes can raise multiplicity concerns because repeated testing can increase the chance of at least one apparently notable result. The registry record does not report a multiplicity strategy or adjusted analyses. The secondary outcomes and follow-up periods therefore provide context about the study's measurement scope, but they do not show which results were designated for confirmatory interpretation.

10. Confidence Intervals and Precision

The primary group percentages are 36.2% for electro-acupuncture and 37.8% for prucalopride. The unadjusted recalculated risk difference is 0.017, with interval endpoints from -0.064 to 0.097. The interval includes values below zero and above zero, indicating that the estimate does not narrowly locate the comparative effect on the risk-difference scale. The interval's confidence level and calculation method are not reported in the registry record.

In general, a confidence interval is a range generated by a statistical procedure to reflect uncertainty in an estimate. Its interpretation depends on the method and the assumptions used. A wider interval allows a broader set of effect values than a narrower interval, but the interval alone does not establish which effects are clinically important. For a noninferiority question, the interval needs to be compared with a prespecified noninferiority margin. That margin is not reported in the registry record, so the displayed interval cannot by itself confirm or rule out noninferiority.

The recalculated p-value is 0.684. It is an unadjusted result and should not be read as a measure of precision or as proof that the groups are equivalent. The registry does not report the sponsor's formal inferential analysis, confidence level, adjustment for other variables, or missing-data method. Those absent details limit how fully the precision can be evaluated.

The group denominators in the primary comparison are 277 and 278. They indicate the numbers used in that posted comparison, but the registry record does not explain whether those participants represent all randomized participants with observed outcomes or how missing outcome data were treated. Precision should therefore be read alongside the uncertainty about analysis population and missingness, rather than as a complete account of all possible sources of uncertainty.

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 participants, for the binary primary outcome. The planning assumptions are a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. The effect used in each planning scenario is a stated fraction of the observed effect: 100%, 75%, or 50% of the observed effect. These are planning illustrations based on the observed effect, not the trial's original design assumptions; the trial's own sample-size assumptions are not reported in the registry record.

The 80% power column gives the number of participants per arm estimated to be needed under those assumptions to have an 80% chance of detecting the specified effect, if that effect and the planning model were correct. The 90% power column gives the corresponding planning number for a 90% chance. For planning at 100% of the observed effect, the figures are 13,131 participants per arm for 80% power and 17,578 participants per arm for 90% power. For planning at 75% of the observed effect, they are 23,289 and 31,177 participants per arm. For planning at 50% of the observed effect, they are 52,275 and 69,981 participants per arm.

Smaller effects require more participants to detect under otherwise unchanged assumptions. These figures are prospective planning illustrations, not observed power for the completed trial. They should not be treated as evidence that the trial did or did not find an effect, nor as a description of the enrollment target used when the trial was designed. The assumptions and effect scenarios define the illustration; the original design rationale is not reported in the registry record.

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 = 0.361; treatment proportion p₁ = 0.378; average p̄ = 0.369.
2. First term: z_1−α/2 × √[2p̄(1−p̄)] = 1.96 × 0.6825 = 1.3378.
3. Second term: z_1−β × √[p₀(1−p₀) + p₁(1−p₁)] = 0.842 × 0.6824 = 0.5744.
4. n = (1.3378 + 0.5744)² / (0.0167)² = 13,130.2, rounded up to 13,131 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 <- 0.36101083032491                          # control proportion
p1 <- 0.377697841726619                          # 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(2047045)
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 = 13,131 (80% power), 17,578 (90% power)
 75% of observed effect: n per arm = 23,289 (80% power), 31,177 (90% power)
 50% of observed effect: n per arm = 52,275 (80% power), 69,981 (90% power)
power.prop.test: 13130.2 
Simulated power at n = 13,131 per arm: 0.796 (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 14 outcome measures, including the primary outcome and 8 secondary outcomes. The secondary measures cover responder proportions and changes in bowel-movement measures across several time windows, along with stool consistency, straining, time to the first CSBM, and constipation-related quality of life. The registry record does not report a prespecified multiplicity strategy, such as an adjustment procedure or a hierarchy for interpreting multiple outcomes. Without that information, results across outcomes and timeframes should not automatically be treated as independent confirmatory tests.

The registry record does not report the sponsor's detailed statistical analysis plan, the model used for the primary comparison, or whether covariate adjustment was planned. The comparative statistics discussed for the primary endpoint are unadjusted recalculations from the posted summary statistics. The registry lists no analysis records. A sponsor's inferential analysis and its specification are not reported in the registry record.

Missing-data handling is also not reported. The record states that 3 electro-acupuncture participants and 2 prucalopride participants withdrew informed consent and were not included in baseline analysis. It does not specify how missing primary outcome measurements were treated, whether any imputation was used, or how participants without an observed endpoint were represented in the analysis. The endpoint description refers to the total cases at baseline as the denominator, while the posted primary comparison uses 277 and 278 participants; further detail about the relationship between those sets is not reported.

The analysis population is not reported in terms of intention-to-treat, per-protocol, or another formal definition. This is particularly relevant to a noninferiority question because interpretation can depend on the analysis population and assumptions about missing outcomes. The registry record also does not report interim analyses, stopping rules, or any prespecified sensitivity analyses. These details should not be inferred from the randomized design or the trial's noninferiority title.

14. 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 0% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: cardiac surgery due to myocardial infarction (0.4%).

The registry reports serious adverse events for 1 of 277 participants at risk in the electro-acupuncture group and 0 of 278 participants at risk in the prucalopride group. The record lists “Cardiac surgery due to myocardial infarction” as the top serious adverse event term, at 0.4%. It does not indicate in the available entry which group this term belongs to or provide further event-level detail. Deaths are not reported in the registry record.

These figures are counts recorded during the reported safety assessment, not a full description of all possible harms. The registry does not report enough detail to assess event timing, duration, relatedness to treatment, severity grading beyond the serious-event category, or how events were collected. A zero recorded serious adverse event in a group does not establish that no risk exists.

The registry separately reports other adverse events affecting 49 of 277 electro-acupuncture participants and 123 of 278 prucalopride participants. Those counts are not the serious adverse event counts and should be interpreted as a separate category. The registry entry does not provide a fuller breakdown of those other events in the registry record. These registry figures are descriptive and do not, on their own, establish a causal comparison or a complete safety profile.

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

The posted primary results show that 36.2% of participants in the electro-acupuncture group and 37.8% in the prucalopride group met the threshold of at least 3 mean weekly CSBMs during weeks 3-8. An unadjusted recalculation gives a risk difference of 0.017, with interval endpoints from -0.064 to 0.097, and a p-value of 0.684. These figures describe the endpoint and analysis as represented in the registry; they do not answer every question about symptoms, sustained effects, quality of life, or safety.

The trial's official title identifies it as a noninferiority study. However, the registry record does not report the margin that defines how much difference would be acceptable for noninferiority, nor the sponsor's formal analysis. The displayed percentages and recalculated statistics therefore cannot establish that electro-acupuncture was noninferior to prucalopride. A non-significant p-value is not proof that treatments are equivalent, and an observed difference should not be described as a treatment benefit or lack of benefit without the relevant analysis and context.

The primary endpoint concerns one threshold over weeks 3-8. It does not capture the full count distribution or all dimensions of constipation. The registry lists later assessment windows and secondary measures, but their results are not reported in the registry record. The study summary also describes an interest in whether effects persist and in patient acceptance, but those results are not included in the posted primary outcome details.

The safety entries are limited as well. Serious adverse event counts are reported, along with a top serious event term, but event details and deaths are not reported in the registry record. The counts should be read as descriptive registry information rather than a complete comparative safety analysis. Overall, the posted data support a narrow description of the primary responder proportions and the unadjusted comparative estimate; broader conclusions require information that is not reported in the registry record.

16. Why This Trial Matters Statistically

This trial illustrates why the label of a study and its posted outcome need to be read together. The official title identifies a noninferiority question, while the primary endpoint is a binary responder measure during weeks 3-8. For noninferiority, the key interpretive reference is a prespecified margin. The registry record does not report that margin or the formal analysis used to assess it, so the percentages alone cannot resolve the trial's stated objective.

The endpoint also shows how a responder threshold simplifies a measure. Classifying participants by whether they reach at least 3 mean weekly CSBMs creates an interpretable proportion, but it does not show how far participants above or below the threshold were from one another. The registry lists other measures that can add context, including changes in weekly CSBMs and spontaneous bowel movements, symptom scores, time to the first CSBM, and quality of life. Their results are not reported in the registry record.

Precision is another important issue. The recalculated risk-difference interval extends from -0.064 to 0.097, covering values on both sides of zero. The interval cannot be interpreted against a noninferiority boundary because that boundary is not reported. This underscores that uncertainty is not resolved simply by a p-value or by noting which group has the numerically higher posted percentage.

Finally, the record identifies several sources of information that matter for interpretation but are not detailed: the analysis population, missing-data handling, multiplicity strategy, and sponsor analysis. The trial therefore offers a useful example of how registry outcome values, comparative uncertainty, and the information needed to evaluate a noninferiority claim are related but not interchangeable.

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 registry record leaves important trial-specific details unreported. Although the official title describes a multicenter noninferiority trial, the noninferiority margin, primary analysis procedure, and sponsor's formal results are not reported in the registry record. Without the margin and its prespecified interpretation rule, the posted figures cannot establish whether the noninferiority objective was met.

The available primary outcome is a responder proportion for weeks 3-8. The record lists a range of later assessment windows and secondary measures, but those results are not reported in the registry record. The outcome data therefore do not show whether the primary-period pattern continued, whether other measures aligned with it, or how acceptability was assessed.

There is limited information about the analysis population and missing observations. The registry notes withdrawals of informed consent and gives the participant denominators used for the posted primary comparison, but it does not describe missing-outcome methods, the treatment of withdrawals in the primary analysis, or whether intention-to-treat and per-protocol analyses were conducted. These omissions are particularly relevant when interpreting a noninferiority design.

The registry does not report the confidence level or construction method for the displayed interval, adjustment for baseline variables, multiplicity procedures, randomization details, or who was masked. The safety record also lacks event-level timing and relatedness information, and deaths are not reported in the registry record. These limitations constrain interpretation of both the comparative efficacy statistics and the descriptive safety counts.

18. Related Tutorials

19. Related Statistical Calculators

20. Sources

• ClinicalTrials.gov: Effect Comparison of Electro-acupuncture and Prucalopride for Severe Chronic Constipation: a Randomized Controlled Trial — NCT02047045.
• Registry record last updated 2021-03-22; status last verified 2021-02.
• Results first posted 2020-01-30.
• 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

NCT02047045 is a completed randomized, single-masked, parallel-group trial comparing electro-acupuncture with prucalopride for severe chronic constipation. The registry records enrollment of 560, with 280 assigned to each group, and gives a start date of 2014-04 and primary completion date of 2016-08. The official title describes a multicenter noninferiority randomized controlled trial.

The primary outcome was the proportion with at least 3 mean weekly CSBMs during weeks 3-8. The posted proportions were 36.2% for electro-acupuncture and 37.8% for prucalopride. The unadjusted recalculated risk difference was 0.017, with interval endpoints from -0.064 to 0.097, and the unadjusted p-value was 0.684.

The registry record does not report the noninferiority margin, sponsor's formal analysis, missing-data method, analysis population, or results for the listed secondary outcomes. Those omissions limit interpretation beyond the posted treatment-period responder proportions.