Physical Therapy Intervention for Puerperal Mastitis: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Physical Therapy Intervention for Puerperal Mastitis (NCT04569136), a randomized na study. The primary outcome is Breast and Nipple Pain.

2. Clinical Question

3. Trial Design

The registry record describes a prospective, randomized, single-center trial with a parallel-group design and single masking. The study was listed as completed and enrolled 37 participants. The record identifies the study sponsor as National Cheng Kung University. The phase is listed as not applicable. It does not give further details about the randomization sequence, allocation concealment, how masking was maintained, or which role was masked; those details are not reported in the registry record.

Three groups were included: an individualized physical therapy intervention, sham ultrasound, and usual obstetric care. The intervention group received education about mastitis and self-management, therapeutic ultrasound, and breast massage. The sham group received education and breast massage as well, but had sham rather than therapeutic ultrasound. The usual-care group received usual obstetric care, which could include verbal advice or printed information about mastitis and breastfeeding. The record does not specify whether other care was prohibited or standardized across groups.

There were 12 participants in the intervention group, 12 in the sham group, and 13 in usual care in the reported primary outcome summaries. The trial's overall enrollment was 37. The primary outcome was breast and nipple pain at 3 months, assessed by numerical rating scale. The registry record also lists seven secondary outcomes, including breast engorgement, breast hardness, body and breast temperature, milk volume, acceptability, adverse events, and breastfeeding self-efficacy.

The registry record does not report a protocol-level sample-size justification, the planned number of analyses, details of an analysis population, or a statistical analysis plan. No primary comparative analysis is posted. The completion status and posted group summaries indicate that results were registered, but the record does not provide enough information to reconstruct all trial conduct or its prespecified analysis approach.

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.

6. Primary Endpoint

The registry lists the primary outcome as Breast and Nipple Pain, measured over 3 months.

The primary endpoint was breast and nipple pain during the past 24 hours at 3 months. Participants were asked to rate breast pain and nipple pain using a numerical rating scale with 11 response points, from 0 for no pain to 10 for the worst possible pain. The registry record describes the primary summary as a median with an inter-quartile range.

Pain is a patient-reported symptom and is directly relevant to the concerns described in the trial rationale. The scale asks participants to describe symptom intensity in their own experience, rather than relying on an observer to infer discomfort from an examination. A score at a single follow-up time can describe the distribution of reported pain in each group, but a comparative treatment effect requires an analysis that contrasts groups and quantifies uncertainty. The posted primary results give group summaries: the intervention group's median was 0, with an inter-quartile range from 0 to 0.75; the sham group's median was 0, with an inter-quartile range from 0 to 0; and the usual-care group's median was 1, with an inter-quartile range from 0 to 2.

These summaries do not show how individual participants' scores changed from baseline, because baseline pain scores are not reported in the registry record. Nor do they by themselves indicate whether group differences are statistically distinguishable or clinically important. A median describes the central position of a distribution, while the inter-quartile range describes its middle portion. Those summaries can be useful when scores are concentrated at the lower end or are not well represented by a mean, but they do not replace a prespecified comparison with uncertainty estimates.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What do the group summaries say?

The primary endpoint is reported as a median and inter-quartile range, rather than as a mean and standard deviation. The median is the middle value when observations are ordered. The inter-quartile range describes the span from the lower to the upper quartile and gives a sense of how spread out the middle half of the observations is. These summaries can be suitable for a rating scale when responses cluster at low scores or when a few higher values could strongly influence a mean. They do not reveal every feature of the distribution: for example, the number of participants at each score is not reported in the registry record.

The intervention and sham groups have the same reported median, while their inter-quartile ranges differ. The usual-care group has a higher reported median and a wider inter-quartile range. These are observations about the posted summaries, not estimates of a treatment effect. Without a comparative model or test and an uncertainty interval, it is not possible to tell how precisely a difference between groups has been estimated. A distribution can be summarized descriptively even when no inferential comparison is posted.

Why is a confidence interval useful?

General statistical explanation: a confidence interval expresses the uncertainty around an estimated quantity under the assumptions of the analysis. For a between-group effect, it helps readers assess both the range of effects compatible with the data and the degree of precision. A point estimate alone cannot do this. The registry record does not report a confidence interval or effect estimate for the primary pain comparison. Consequently, the size and precision of a primary between-group difference cannot be assessed from the posted results.

The registry does include an unadjusted risk-difference comparison for acceptability between intervention and usual care, with a reported p-value of 0.035. The corresponding interval lies below zero for the defined comparison, while the intervention-versus-sham interval includes zero. These interval patterns describe the estimates as posted, but they do not resolve the larger concerns that arise when an outcome is secondary and several outcomes may have been considered. The registry does not report an adjusted comparison or an analysis plan for multiplicity.

How should the randomized design be understood?

General statistical explanation: random allocation is intended to make groups comparable, on average, with respect to measured and unmeasured characteristics at the start of a trial. It does not guarantee balance in a small trial, and it does not remove the need to report baseline characteristics, follow-up, and an appropriate analysis. The registry record labels the study randomized, but does not report the sequence-generation method, allocation concealment, or baseline group summaries. The posted record also does not identify the masked role in detail, beyond listing single masking and describing assessor blinding in the study summary.

The sham group is especially informative for distinguishing the contribution of therapeutic ultrasound from elements shared across the intervention and sham approaches. Both groups received education and massage, while one received therapeutic ultrasound and the other sham ultrasound. A direct comparison of these groups would therefore address a narrower contrast than a comparison with usual care. The primary group summaries are posted, but no primary inferential comparison is reported for either contrast.

What is the role of the sample-size illustration?

General statistical explanation: planning calculations estimate how many participants would be needed under stated assumptions to detect an effect with a chosen probability, often called power. The registry's planning illustration is based on the observed acceptability effect for the intervention-versus-usual-care comparison, rather than on a design justification for this trial. It uses a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. The illustration gives participants per arm for 80% power and for 90% power, with scenarios planning for 100%, 75%, and 50% of the observed effect.

Those planning figures are not observed power and should not be read as proof that the actual trial was adequately or inadequately powered. They are hypothetical sample-size illustrations based on an observed secondary result. An effect estimated in a small sample can be unstable, and choosing a fraction of that result does not establish that the corresponding effect is clinically meaningful. The registry record does not report the trial's own sample-size justification, so it is unknown whether the original design used different assumptions or a different endpoint.

Why do unadjusted secondary tests need caution?

General statistical explanation: when multiple outcomes or comparisons are tested, the chance of obtaining at least one apparently noteworthy result can increase even if none represents a genuine effect. Adjustments or a prespecified hierarchy can address that concern, but the registry record does not report such a strategy. The acceptability comparison with p = 0.035 is explicitly unadjusted in the posted results. It should therefore be interpreted alongside the full set of planned outcomes, not in isolation.

Small group sizes also make binary results sensitive to the outcomes of a few participants. A risk difference summarizes the difference in the observed proportions, while a confidence interval indicates uncertainty around that difference. The acceptability comparison's interval is broad, and its lower and upper limits fall on different sides of the null for intervention versus sham; for intervention versus usual care, the posted interval is entirely on one side. These are statistical features of the estimates, not evidence by themselves of a stable or clinically important effect. The registry record does not report a complete analysis plan or adjusted secondary results to clarify how the findings were selected or interpreted.

10. Multiplicity, Missing Data and Analysis Populations

The registry record lists one primary outcome and seven secondary outcomes. The primary outcome is breast and nipple pain, measured at 3 months. Secondary outcomes include other breast symptoms, temperature, milk volume, acceptability, adverse events, and breastfeeding self-efficacy. It does not report a statistical analysis plan specifying a hierarchy among these outcomes, a family of comparisons, or an adjustment for multiple testing. It also does not report whether the posted analyses were prespecified.

This matters because multiple outcomes and group contrasts create multiple opportunities for an apparently notable result. The acceptability comparison between intervention and usual care has an unadjusted p-value of 0.035. Without information about the testing plan and multiplicity handling, that value should not be interpreted as if it arose from a single prespecified confirmatory test. No adjusted secondary result is reported in the registry record.

Information about missing data and analysis populations is also limited. The primary summaries report 12 participants in the intervention group, 12 in sham, and 13 in usual care, matching the total enrollment of 37. The record does not explain whether every randomized participant contributed a primary outcome, how missing follow-up observations were handled, whether participants were analyzed according to their randomized groups, or whether any per-protocol or other analysis population was used. The number of participants with missing data at the 3-month assessment is not reported in the registry record.

These omissions affect interpretation even when descriptive values are available. If participants with missing outcomes differ from those with observed outcomes, group summaries may not represent all randomized participants in the same way. General statistical explanation: an analysis plan that states how missing outcomes and multiple comparisons will be handled helps limit selective analysis and makes estimates easier to interpret. In its absence, readers should distinguish clearly between the posted descriptive summaries and claims that would require a prespecified comparative analysis. The registry record does not report interim analyses, a missing-data strategy, or a primary analysis population.

11. 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 adverse-event summaries record zero serious adverse events, zero other adverse events, and zero deaths in the intervention group, the sham group, and the usual-care group. The numbers at risk were 12 in each of the first two groups and 13 in usual care. These are the event counts recorded for the groups in the registry record.

Zero observed events is not the same as evidence that an intervention cannot cause harm. With small groups, uncommon events may not occur during the observed follow-up even if they are possible. General statistical explanation: the absence of observed events leaves uncertainty about the underlying event rate, and that uncertainty is greater when few participants are observed. The registry record does not provide further detail about the methods or timing of adverse-event collection, the completeness of safety follow-up, or whether all events were actively solicited.

The posted summaries also do not identify specific non-serious event terms. The registry record lists no top serious event terms. The appropriate conclusion is limited to the reported counts: no serious or other adverse events and no deaths were recorded in these group summaries. These figures do not establish comprehensive safety or exclude risks that were not observed or not reported.

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

The posted primary data describe low pain scores at the 3-month assessment in the intervention and sham groups, and a higher median in usual care. They show the distribution summaries recorded for the groups, not the change in pain from before treatment, because baseline scores are not reported in the registry record. They also do not provide a formal estimate of the primary between-group difference. It is therefore not possible to draw a firm comparative conclusion about pain from the posted primary results.

The acceptability comparison between intervention and usual care is a secondary, unadjusted finding. It may be relevant to how participants received the intervention program, but it does not answer the primary pain question. The registry record does not report whether multiplicity was addressed, and the groups are small. Those features make the result less secure as a confirmatory claim. Other listed secondary outcomes do not have comparative estimates reported in the registry record.

The trial's three-group structure distinguishes two contrasts. Intervention versus sham compares therapeutic ultrasound with sham ultrasound in the context of shared education and massage. Intervention versus usual care compares the full individualized program with care that may include advice or printed information. These contrasts answer different questions and should not be collapsed into one general claim about physical therapy. The registry record does not report a primary statistical comparison for either contrast.

The event summaries record no adverse events or deaths, but they cannot establish that the approaches are risk-free. The small number of participants and limited safety detail constrain what can be inferred from zero counts. More broadly, a registry result is a record of posted outcome summaries and analyses, not a complete account of every detail needed to judge trial conduct. The missing analysis plan, baseline information, missing-data approach, and primary effect estimate leave important interpretive questions unresolved.

General statistical explanation: an observed difference is not automatically a causal or clinically meaningful difference. Randomization supports causal interpretation when allocation, follow-up, and analysis are adequately documented, but randomization alone does not guarantee precise estimates or remove uncertainty. The results should therefore be described narrowly: group pain summaries and acceptability counts are posted, while a comparative primary pain analysis is not reported. No medical conclusion about the benefit or lack of benefit of the intervention follows from these summaries alone.

13. Why This Trial Matters Statistically

This trial is statistically informative as an example of the difference between descriptive results and an analysis that directly answers a comparative research question. The primary endpoint is measured and summarized by group, but no primary comparative estimate or uncertainty interval is reported. Readers can see the group-level medians and inter-quartile ranges, yet cannot judge the size or precision of a between-group effect using the registered results. That distinction is central when interpreting clinical research: descriptive summaries are useful, but they do not by themselves quantify evidence for a contrast.

The three-arm design also makes the choice of comparison important. Therapeutic ultrasound is contrasted with sham ultrasound in groups that also receive education and massage, while usual care provides a broader comparison with a less specified care package. A single interpretation of “physical therapy” would obscure these different contrasts. Clear reporting of the planned primary comparison and its analysis would help readers understand which component or package the evidence addresses.

The acceptability outcome illustrates another statistical issue. Its unadjusted comparison with usual care has a reported p-value of 0.035, but it is secondary and the registry record does not describe multiplicity handling. A result that appears notable in one analysis can be less persuasive when considered among multiple outcomes and comparisons. Reporting the analysis hierarchy, effect estimates, and uncertainty for all planned outcomes would make the finding more interpretable.

Finally, the sample-size illustration is based on an observed secondary effect rather than a reported design justification. It is a planning aid, not evidence of observed power and not a substitute for the trial's original sample-size rationale. The record's missing details about analysis populations, missing observations, and masking also demonstrate why transparent methods reporting matters alongside outcome numbers. These limitations do not erase the descriptive information, but they define how far statistical interpretation can responsibly go.

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.

Several trial-specific reporting limitations constrain interpretation. Although the study is described as randomized and assessor-blinded, the registry record does not report the randomization method, allocation concealment, or which assessor role was masked. It does not provide baseline group characteristics or baseline pain summaries. Without those details, readers cannot assess initial group comparability from the posted record or understand the extent of any masking protections.

The primary pain summaries are reported at 3 months, but the record does not provide a comparative estimate, confidence interval, or p-value. It also does not report participant-level change from baseline. The reported median and inter-quartile range values are descriptive and do not reveal the full score distributions. No information is posted about missing primary observations or the handling of missing data, and the record does not define an analysis population.

The intervention was individualized and combined education, therapeutic ultrasound, and massage. The sham group received education and massage with sham ultrasound, while usual care could include advice or printed information. The registry record does not describe the content, dose, timing, or adherence for these elements in enough detail to assess consistency across participants. Usual care is not described as a fixed treatment protocol, limiting the specificity of that comparison.

Comparative details for secondary outcomes are incomplete in the registry record. The available acceptability comparison is unadjusted, and no multiplicity strategy is reported. The trial's own sample-size rationale and full statistical analysis plan are not reported. Safety summaries list no events, but details of event ascertainment and follow-up completeness are also absent. These limitations are specific to the information available for this trial and mean that the posted results support description more readily than definitive comparative interpretation.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Physical Therapy Intervention for Puerperal Mastitis — NCT04569136.
• Registry record last updated 2024-07-18; status last verified 2024-02.
• Results first posted 2024-07-18.
• 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

The registry record describes a completed, randomized, single-center, parallel-group trial of physical therapy for puerperal mastitis in breastfeeding women. It lists single masking and an enrollment of 37 participants. The three groups received individualized physical therapy with therapeutic ultrasound, sham ultrasound alongside education and massage, or usual obstetric care.

The primary outcome was breast and nipple pain during the previous 24 hours at 3 months, measured on an 11 point numerical rating scale and summarized by median and inter-quartile range. The group summaries are posted, but no primary comparative analysis is reported. Seven secondary outcomes are listed; acceptability results include an unadjusted intervention-versus-usual-care comparison with p = 0.035.

The registry record does not report the trial's sample-size justification, detailed statistical analysis plan, missing-data methods, or analysis population. Adverse-event summaries record no serious or other adverse events and no deaths in any group. These results should be interpreted as limited descriptive and secondary evidence rather than as a complete comparative analysis of the primary pain question.