A Crossover Study on the Blinding Effect of a New Pragmatic Placebo Needle: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for A Crossover Study on the Blinding Effect of a New Pragmatic Placebo Needle (NCT01948375), a randomized na study. The primary outcome is Proportion of Volunteers'Perception of Needle Penetration Between the Pragmatic Placebo Needle and Real Needle..

2. Clinical Question

The question concerns perception and masking, not whether acupuncture improves a health condition. A placebo needle is intended to provide a comparison procedure while resembling the real procedure. For blinding to be evaluated, the relevant issue is whether participants’ perceptions differ between the real and placebo needles. The registry describes the outcome as the proportion of volunteers’ perception of needle penetration between the two needles. It also notes that the primary outcome has several categories or time points, and it does not reduce those details to one reported comparison.

The registry lists “Device Ineffective” as the condition. That listing does not establish that the study tested clinical effectiveness. Its stated primary objective was to assess blinding, while its secondary objective was to explore factors that might influence blinding. The secondary outcomes concern needle sensation, acupuncture pain, and acceptability.

The primary numerical result, including the comparison between needle types, is not reported in the registry record. The clinical question can therefore be identified, but the posted information does not establish how participants’ perceptions differed or how precisely that difference was estimated.

3. Trial Design

This was a randomized, single-masked, crossover study. Enrollment was 60, and the registry marks the study as completed. The two sequences were real needle followed by pragmatic placebo needle, and pragmatic placebo needle followed by real needle. In each sequence, participants received acupuncture with both needle types, but in a different order.

In a crossover design, each participant experiences more than one study condition. General statistical context: this can allow a comparison of conditions within the same participant, but the analysis needs to account for the paired nature of those observations. The registry record does not report the statistical method used for the primary comparison, nor does it say whether the analysis accounted for period or sequence effects.

The record identifies the study as randomized and single masked, but does not report who was masked or how masking was maintained. Details of the randomization procedure, the length of each period, any washout interval, and the timing between periods are not reported in the registry record. These details can matter when interpreting a crossover study, particularly if experience in one period might influence responses in another.

The study started in 2013-08, with primary completion in 2013-12. Its phase is listed as NA. The sponsor is Guang'anmen Hospital of China Academy of Chinese Medical Sciences. The registry lists the primary assessment as occurring in the third acupuncture session in each period. It does not report further details about session spacing or the conduct of the assessment.

The registry describes four secondary outcome measures: type and degree of needle sensation using the Southampton Needle Sensation Questionnaire, degree of acupuncture pain, and acceptability of the acupuncture needle. The record lists five outcome measures and four analyses, but does not explain the relationship between those counts or provide a complete 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.

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.

6. Primary Endpoint

The registry lists the primary outcome as Proportion of Volunteers'Perception of Needle Penetration Between the Pragmatic Placebo Needle and Real Needle., measured over in the third acupuncture session in each period.

The primary endpoint concerns volunteers’ perception of needle penetration when they received the pragmatic placebo needle and the real needle. The assessment was specified for the third acupuncture session in each period. The outcome description refers to the proportion of volunteers’ perception between the two needle types, but the registry notes that the primary outcome has several categories or time points and is not reduced to one comparison.

This endpoint is used to address the trial’s stated aim of validating the blinding effect of the new pragmatic placebo needle. General context: blinding assessments examine whether participants can distinguish assigned procedures or treatments. If perceptions differ systematically between a placebo procedure and the real procedure, that may be relevant to whether participants remained unaware of which procedure they received. Perception is not itself a measure of clinical benefit, and it cannot establish the effectiveness of acupuncture.

The registry record does not report the observed category counts, a proportion, or a statistical comparison for this endpoint. It also does not provide the response options, the precise rule for classifying a participant’s perception, or a definition of how the proportion was calculated. Without those details and the outcome values, the direction and precision of the observed result cannot be interpreted from the registry record.

The selected assessment time is described as the third session in each period. The record does not explain why that session was chosen, how earlier perceptions were handled, or whether all participants contributed an assessment in both periods. Those details are not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does the crossover design imply?

The study used a crossover design: each sequence received both the real needle and the pragmatic placebo needle, in opposite orders. General statistical context: crossover data contain repeated observations from each participant. A comparison can use the fact that each participant serves as their own reference, but the observations are not independent. An appropriate analysis usually needs to represent that within-participant relationship. The registry record does not report the model or test used, so it is not possible to determine how the analysis handled the repeated observations.

Order may matter as well. In a crossover study, period effects describe differences that may arise because observations occur at different stages, while sequence effects concern the order in which conditions are received. Carryover describes an influence from an earlier period that persists into a later period. These are general design concepts, not reported findings about this trial. The registry record does not report whether period, sequence, or carryover effects were assessed, or whether a washout interval was used.

How should a perception outcome be summarized?

The primary endpoint concerns volunteers’ perception of needle penetration in the third session of each period. The record indicates that the outcome has several categories or time points and is not reduced to one comparison. General statistical context: a categorical outcome can be described by counts or proportions in each response category. A comparison can then focus on a prespecified contrast, but the contrast needs to be stated clearly so readers know which response patterns it addresses. In paired data, the relationship between each participant’s responses across conditions is also relevant.

The registry record does not report the response categories, their counts, or the specific statistical contrast. It also does not state whether the primary analysis compared paired responses, used a model for categorical repeated measures, or followed another approach. No method can be attributed to the investigators from the information in the record.

What do confidence intervals and p-values convey?

General statistical context: an estimate gives a numerical summary of a contrast in the observed data. A confidence interval expresses uncertainty about that estimate under the assumptions of the method. A narrower interval generally indicates greater precision than a wider interval, while the interval’s position indicates which effect sizes are compatible with the data and method. A p-value evaluates the data against a specified null model; it does not measure the probability that a treatment or procedure works.

Neither a primary estimate nor its confidence interval or p-value is reported in the registry record. The primary result therefore cannot be interpreted for magnitude, uncertainty, or statistical compatibility with a null comparison. Even if a p-value were available, it would not replace an estimate of the contrast or its precision.

What does the sample-size illustration represent?

The registry describes a planning illustration based on the observed effect, with a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. It defines the effect to detect as a stated fraction of the observed effect. Such calculations are planning illustrations, not observed power and not evidence about the outcome. The record does not report the numerical illustration values or the observed effect used to produce them. It also does not report the trial’s own sample-size justification, so the illustration should not be read as the study’s original design rationale.

General statistical context: a planning calculation depends on its assumptions, including the target effect and the chosen error rate. Changing those assumptions changes the planning result. A calculation based on an observed effect is especially dependent on that estimate, which is not reported. Without the numerical inputs and results, the illustration cannot be independently interpreted as a statement about the adequacy of enrollment.

What information is missing for a full statistical assessment?

The registry record does not report a detailed analysis plan, the primary test or model, the primary estimate, measures of uncertainty, or the handling of missing observations. It also does not report whether analyses were prespecified, whether interim analyses took place, or how the crossover structure was handled. These are not interchangeable details: the model describes how the data are analyzed, missing-data methods address incomplete observations, and multiplicity methods address the interpretation of multiple analyses. Their absence limits reproducibility and assessment of the reported findings, but does not establish that a particular method was or was not used outside the registry record.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists five outcome measures and four analyses. It identifies the primary outcome as volunteers’ perception of needle penetration and lists secondary outcomes concerning needle sensation, acupuncture pain, and acceptability. The record does not explain how the five measures relate to the four analyses, identify all planned comparisons, or report a multiplicity strategy. It is therefore not possible to determine whether or how the analysis accounted for examining multiple outcomes or contrasts.

General statistical context: when several hypotheses are tested, the chance of at least one apparently unusual result can increase if each test is interpreted separately. A multiplicity plan may identify a primary comparison, adjust error rates, or treat secondary analyses as exploratory. The registry record does not report which approach, if any, was used. The stated primary objective and outcome identify the principal topic, but do not establish a complete testing hierarchy.

Missing-data methods and analysis populations are also not reported in the registry record. The record gives enrollment of 60, but does not state how many participants completed both periods, contributed the primary assessment, or were included in each analysis. It does not describe exclusions, imputation, or sensitivity analyses. Consequently, the enrollment count should not be assumed to be the denominator for the primary outcome.

The record does not report whether the primary analysis followed an intention-to-treat, per-protocol, or other population definition. It also does not report how incomplete paired observations were handled. These omissions leave uncertainty about the analyzed population and the robustness of the outcome analysis. They do not by themselves show that observations were missing or that a particular analysis was inappropriate.

11. 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.

The registry lists safety counts separately for the real-needle-then-placebo-needle sequence and the placebo-needle-then-real-needle sequence. Each listed sequence has 30 participants at risk for serious adverse events and 30 at risk for other adverse events. The posted counts show zero serious adverse events and zero other adverse events in each sequence.

These are counts recorded for the listed groups. Because the study is a crossover trial, the group labels describe treatment order rather than two groups that received only one needle type throughout. The safety counts should therefore be read in the context of the sequences and periods described in the record, not as a direct treatment-specific comparison of exposure to one needle alone.

The registry does not report deaths as a numerical count; that information is not reported in the registry record. The absence of reported adverse events in these entries does not establish that no events occurred outside the recorded categories or reporting period, and it does not establish comparative safety. The record does not provide event definitions, collection procedures, exposure durations, or further detail about safety follow-up. The posted counts describe what is recorded, but do not support a broader safety conclusion.

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

The study was designed to examine whether volunteers’ perceptions differed between a pragmatic placebo acupuncture needle and a real needle. Its randomized crossover design assigned participants to receive both procedures in one of two orders. The primary assessment was specified for the third acupuncture session in each period. These features identify the study question and structure.

The registry record does not report the primary outcome values or a statistical comparison. As a result, the available information does not show whether participants’ perceptions were similar or different between the needle types, nor does it indicate the precision of such a comparison. The stated objective is not a result, and the completed status does not fill the gap in outcome reporting.

General statistical context: a blinding assessment concerns whether participants can distinguish procedures; it is not a direct test of clinical effectiveness. Even a reported perception comparison would need to be interpreted in light of its response categories, analysis method, missing observations, and uncertainty. Here, those outcome and analysis details are not reported in the registry record.

The recorded safety entries show zero serious and zero other adverse events in each listed sequence, with 30 participants at risk in each category. Deaths are not numerically reported. These safety counts are descriptive entries and do not establish a broader comparative safety conclusion.

The appropriate reading is therefore limited: the registry documents a trial intended to assess the blinding effect of a pragmatic placebo needle, but it does not provide the primary findings needed to determine what the assessment showed. No conclusion about success or failure of blinding, or about clinical benefit, follows from the design description alone.

13. Why This Trial Matters Statistically

This trial addresses a methodological question in acupuncture research: whether a pragmatic placebo needle can serve as a credible comparison procedure for studies involving a real needle. The registry describes the placebo needle as a device whose blinding effect had not yet been validated and states that validation was the primary objective. That makes participant perception, rather than clinical efficacy, the central statistical issue.

The crossover structure is statistically relevant because participants received both needle types in different orders. General statistical context: paired comparisons can use within-participant information, but they require analysis that reflects the dependence between observations. Period and sequence effects may also matter. The record does not report how these issues were handled, so the design raises questions that cannot be resolved from the registry description alone.

The endpoint description also highlights the importance of transparent outcome definitions. The primary outcome is described as a proportion related to perceived needle penetration, while the record notes multiple categories or time points and does not reduce them to one comparison. Reporting the response distribution, the planned contrast, and its uncertainty would be important for interpreting a blinding assessment. Those results are not reported in the registry record.

The study is statistically informative as a design example because it makes clear that evaluating a placebo device is not the same as testing a treatment’s clinical effect. Yet the record’s lack of primary numerical results and analysis details limits what can be learned about the observed performance of the device. Clear reporting of outcome categories, paired analyses, missing data, and precision would allow readers to distinguish the design rationale from the evidence produced by the study.

14. 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 main limitation for interpretation is that the registry record does not report the primary outcome result. The endpoint description says that perception was assessed in the third acupuncture session in each period, but gives no response counts, estimate, or measure of uncertainty. It also indicates several categories or time points without specifying a single comparison. This prevents assessment of the direction, magnitude, or precision of the blinding outcome.

Important crossover details are not reported in the registry record. The record does not state who was masked, how randomization was implemented, how long periods lasted, whether a washout interval was used, or whether period, sequence, or carryover effects were assessed. The statistical method for the primary comparison is also not reported. These omissions make it difficult to evaluate whether the analysis matched the repeated-measures design.

The participant flow and analysis population are not described. Although enrollment was 60, the record does not report how many participants completed both periods or contributed the primary endpoint. Missing-data handling and exclusions are not reported. The registry also does not provide participant characteristics or detailed eligibility criteria.

The record lists secondary outcomes and counts of measures and analyses, but does not give a complete analysis plan or multiplicity approach. It does not report the trial’s sample-size justification. Safety reporting is limited to the posted counts by sequence; deaths are not numerically reported, and further safety collection details are absent. These limitations describe gaps in the registry information and do not establish what may have been reported elsewhere.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: A Crossover Study on the Blinding Effect of a New Pragmatic Placebo Needle — NCT01948375.
• Registry record last updated 2018-01-09; status last verified 2017-12.
• Results first posted 2014-07-08.
• 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.

18. Record Summary

NCT01948375 is a completed randomized, single-masked crossover study titled “A Crossover Study on the Blinding Effect of a New Pragmatic Placebo Needle.” Enrollment was 60. Participants were assigned to receive real needle followed by pragmatic placebo needle, or the reverse sequence. The sponsor was Guang'anmen Hospital of China Academy of Chinese Medical Sciences. The study started in 2013-08, and primary completion was 2013-12. The phase is listed as NA.

The primary objective was to validate the blinding effect of the pragmatic placebo needle. The primary endpoint concerned volunteers’ perception of needle penetration in the third acupuncture session in each period. Secondary outcomes concerned needle sensation, acupuncture pain, and acceptability.

The registry record does not report the primary outcome result, its statistical uncertainty, or the analysis method. It also does not report missing-data handling, the analysis population, or a multiplicity plan. Safety entries record zero serious and zero other adverse events in each sequence, with 30 participants at risk in each category; deaths are not numerically reported.