Study of the Inflammation and Airway Changes That Occur After Exposure to Allergen in Asthmatics: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Study of the Inflammation and Airway Changes That Occur After Exposure to Allergen in Asthmatics (NCT02230189), a na phase 2 study. The primary outcome is Difference in Expression of Epithelial miRNAs (in Read Counts) 24 Hours After Allergen-challenge as Compared to 24 Hours After Diluent Challenge in Participants With Allergic Asthma.

2. Clinical Question

3. Trial Design

This was a completed Phase 2, single-group mechanistic study, with enrollment recorded as 28. Allocation is listed as not applicable and masking as none. The registry summary describes a study of airway changes after allergen exposure, rather than a randomized comparison of treatment groups. For the primary endpoint, allergen and diluent were instilled into separate lung segments in the same participant, creating a within-participant comparison.

The brief summary describes three visits over approximately 14 days. At the first visit, participants underwent characterization that included lung function, methacholine challenge, and allergen skin prick testing. At the second visit, they underwent bronchoscopy with segmental allergen administration. At the third visit, either 24 hours or 7 days later, bronchoscopy was used to collect airway samples, including bronchoalveolar lavage, epithelial brushings, and endobronchial biopsies.

The summary describes participants with asthma as well as allergic and non-allergic volunteers without asthma. It says the primary outcome was restricted to allergic asthmatics. The brief summary also describes a total of 38 subjects, including 26 asthmatics with stable or well-controlled asthma, 6 allergic non-asthmatics, and 6 non-allergic subjects; that sentence is incomplete in the registry record. The enrollment field lists 28, and the record does not explain the difference between that figure and the summary’s stated total.

The study was designed to examine biological responses, including miRNA and mRNA expression and cell-related measures. Its single-group structure and segment-level control do not make it a randomized trial of clinical treatment. No treatment-effect comparison between independent arms is reported.

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:

Analysis population for the primary outcome, as defined in the registry: Our pre-specified primary outcome was limited to Allergic Asthmatics only. The rationale for this is that participants without allergy or asthma do not respond to Allergen Challenge and therefore the changes in miRNA are uninformative.

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 Difference in Expression of Epithelial miRNAs (in Read Counts) 24 Hours After Allergen-challenge as Compared to 24 Hours After Diluent Challenge in Participants With Allergic Asthma, measured over 24 hours.

The primary endpoint concerns epithelial miRNA expression in participants with allergic asthma. Airway epithelial brushings were collected at baseline and 24 hours after allergen and diluent were instilled into separate lung segments. RNA sequencing was used to generate transcript read counts, which underwent variance-stabilized log normalization. For each miRNA, the analysis compared the change from baseline in the allergen-challenged segment with the change from baseline in the diluent-challenged segment.

The registry identifies the measure as a mean, with standard deviation as the dispersion measure, and gives the unit as normalized log2 copy number. The endpoint is intended to characterize a mechanistic response in airway tissue, not a clinical outcome such as symptoms, exacerbations, or lung-function benefit. The investigators state that the direction of change does not have clinical significance in this mechanistic study.

Using diluent as a within-participant comparator can help distinguish changes associated with allergen challenge from changes seen after the control instillation. The comparison still depends on the sampling and modeling approach, and the registry record does not report the underlying estimates, their uncertainty, or the miRNA-specific findings. Those results are therefore not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

How does the within-participant comparison work?

Each participant in the primary population had an airway segment exposed to allergen and another exposed to diluent. The registry description says epithelial samples were collected from both segments 24 hours later, with baseline samples also used in the analysis. The model estimated the change from baseline for the allergen sample and the change from baseline for the diluent sample, then compared those changes. This is a paired or within-participant contrast in the sense that the two challenge conditions are observed in the same participant.

In general, a within-participant design can reduce the influence of characteristics that remain relatively stable across the paired measurements, because those characteristics are shared by the participant. It does not remove every source of bias or variation. Differences between lung segments, sampling, or challenge conditions may still matter. The registry record does not report whether segment assignment was randomized or whether laboratory personnel were masked.

What does the normalized log2 measure represent?

The endpoint uses RNA sequencing read counts processed with variance-stabilized log normalization. Read counts are measurements of how many sequencing reads are assigned to a transcript; they are not direct counts of functioning cells or a direct measure of clinical severity. Normalization is used to make expression measurements more comparable despite differences in sequencing scale and data variability. A log transformation places expression values on a scale where relative changes can be analyzed more effectively.

As a general statistical point, log-scale outcomes are interpreted on the transformed scale used in the analysis. The registry labels the unit as normalized log2 copy number and describes the endpoint as a mean with standard deviation. It does not report the observed mean differences or standard deviations, so the magnitude and precision of the expression changes cannot be evaluated from the registry record.

Why use a regression model?

The record says a regression model estimated the change from baseline for each participant and miRNA in each challenge condition. Regression provides a framework for estimating an association or contrast while representing variation in the observed measurements. The registry description does not give the model formula, covariates, assumptions, handling of repeated measures, or diagnostic checks. Those details are not reported in the registry record and should not be inferred.

In general, estimates are more informative when accompanied by uncertainty measures, such as standard errors or confidence intervals. A confidence interval describes a range of values compatible with the data and model under its assumptions; it helps readers assess precision rather than only whether a threshold was crossed. The registry identifies standard deviation as the endpoint’s dispersion measure but does not report confidence intervals or other uncertainty results for the primary endpoint.

What does an unadjusted p-value threshold mean?

The endpoint description says statistical significance was assessed using an unadjusted p-value threshold of <0.05. A p-value is a measure of how incompatible observed data are with a specified null model, assuming that model and the analysis assumptions are appropriate. It does not measure the probability that a biological hypothesis is true, nor does it quantify the size or clinical importance of a change.

Unadjusted testing evaluates each comparison without correcting for the number of tests considered. In general, when many outcomes are tested, the chance of at least one small p-value arising by chance can increase. Multiplicity procedures can address that issue, but no such procedure is reported in the registry record. The record also does not provide the list of miRNAs tested or their individual p-values. Accordingly, it is not possible to judge the pattern of results or the role of multiple testing.

How should planning calculations be understood?

Any sample-size illustration based on an observed effect is a planning exercise, not an observed trial result and not observed power. The stated assumptions for such an illustration are a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation, with the target effect expressed as a fraction of the observed effect. The record describes those as planning assumptions rather than the trial’s own design.

Those assumptions do not describe this study’s primary comparison, which is within participants and is not a two-arm randomized comparison. The registry record does not report a protocol sample-size justification or a statistical plan that connects a planning illustration to the actual mechanistic design. A planning calculation should therefore not be read as evidence that the study had adequate power to detect its primary endpoint.

10. Multiplicity, Missing Data and Analysis Populations

The primary endpoint description says miRNA significance was assessed using an unadjusted p-value threshold of <0.05. The registry record does not report a correction for testing multiple miRNAs, a hierarchy of primary and secondary tests, or a family-wise or false-discovery procedure. It also does not give a complete set of miRNA-specific p-values or estimates. With multiple molecular measurements, an unadjusted threshold alone does not describe the overall false-positive risk across all tests.

The record identifies allergic asthmatics as the pre-specified primary population and states that the primary outcome was limited to this group. It does not describe the size of the analysis population for the primary endpoint, the number of samples successfully analyzed, or how participants with incomplete measurements were handled. Missing-data methods, exclusions, and reasons for missing samples are not reported in the registry record.

The registry lists an enrollment of 28, while its brief summary describes a total of 38 subjects and is incomplete. It does not explain this difference or state how many participants contributed to the primary miRNA analysis. The adverse-event group counts should not be treated as endpoint analysis denominators. The record also does not describe whether all participants were analyzed according to a defined analysis population or whether any sensitivity analyses were performed. These omissions limit assessment of selection, missingness, and the robustness of the primary analysis.

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 3% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: pregnancy identified during study enrollment (4.5%).

The registry lists serious and other adverse-event figures separately for allergic asthmatics, allergic non-asthmatics, and non-allergic non-asthmatics. For allergic asthmatics, the record lists 22 at risk for serious adverse events and 1 affected; for other adverse events, it lists 22 at risk and 2 affected. For allergic non-asthmatics, it lists 2 at risk and none affected in either category. For non-allergic non-asthmatics, it lists 4 at risk and none affected in either category. Deaths are listed as 0 for each group.

The record identifies “Pregnancy identified during study enrollment” as a top serious term, with 4.5%. It does not provide enough detail in these figures to characterize the circumstances, timing, or relationship to study procedures. The figures are descriptive registry entries; they do not establish that an event was caused by a challenge or procedure, and they do not support a comparison of risk between groups. The record does not report a causal assessment or additional detail about event severity and timing in the information available for this summary.

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

The study addresses a biological question: whether epithelial miRNA expression changes differently after allergen challenge than after diluent challenge in participants with allergic asthma. The registry describes how airway samples were collected and how normalized RNA sequencing read counts were compared. This provides context for understanding the intended measure and the within-participant contrast.

However, the registry record does not report the primary endpoint estimates or their uncertainty. It is therefore not possible to state whether expression increased or decreased, whether any specific miRNA met the stated unadjusted threshold, or how large or precise an observed difference was. The endpoint description is not itself evidence of an observed change.

Even if expression differences were reported, they would be mechanistic findings rather than direct evidence of a clinical effect. The registry states that the direction of change does not have clinical significance. The study does not establish from the information in the registry whether any molecular changes correspond to symptoms, asthma control, or other clinical outcomes.

The within-participant diluent comparison helps frame the biological contrast, but the record does not report all design details needed to assess possible sources of bias, including whether segment assignment was randomized. The analysis was restricted to allergic asthmatics for the primary outcome, so it would not automatically apply to other participant groups described in the study.

The most defensible interpretation is limited: the registry describes a mechanistic study and its intended analysis, but the primary result is not reported in the registry record. No conclusion about the presence, size, or clinical importance of an allergen-associated miRNA response can be drawn from the endpoint description alone.

13. Why This Trial Matters Statistically

This study illustrates how a clinical investigation can use a biological endpoint to examine a mechanism rather than test a clinical treatment outcome. Its primary comparison is between allergen and diluent responses in separate airway segments within participants. That structure differs from a randomized comparison between independent treatment groups and calls for interpretation aligned with the actual contrast.

The endpoint also makes the distinction between statistical and clinical meaning important. A change in normalized miRNA read counts may describe molecular activity, but the registry explicitly cautions that the direction of change does not have clinical significance. Statistical significance, if reported, would not by itself establish a clinically important effect.

The record’s use of an unadjusted threshold for miRNA testing highlights why multiplicity matters in molecular studies. When many measures are assessed, readers need to know whether and how the analysis accounts for multiple comparisons. Without the full results and multiplicity approach, isolated significance claims would be difficult to evaluate.

Finally, the registry record demonstrates the value of reporting estimates and uncertainty, not only an endpoint definition. It identifies the biological question and analysis framework but does not report the primary endpoint findings. The mismatch between the enrollment entry and the summary’s stated total also leaves the analyzed population unclear. These limits affect how confidently readers can assess the study’s evidence, irrespective of the underlying scientific rationale.

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 primary outcome results are not reported in the registry record. No miRNA-specific estimates, standard deviations, confidence intervals, or p-values are available in the described information, so effect magnitude and precision cannot be assessed.

The registry does not report the regression model specification, covariates, assumptions, or diagnostic checks. It also does not state whether segment assignment was randomized, whether laboratory assessments were masked, or how potential differences between lung segments were handled. Masking is listed as none, but the record does not explain which study procedures or assessments were unmasked.

The record gives an enrollment of 28, while the brief summary describes a total of 38 subjects and is truncated. It does not reconcile these figures or report how many participants contributed to the primary endpoint analysis. Missing data, exclusions, and the treatment of incomplete RNA sequencing measurements are not described.

The primary analysis was restricted to allergic asthmatics, limiting the intended population for the endpoint. The record does not report a multiplicity adjustment despite describing unadjusted testing for miRNAs. It also does not provide enough results to assess consistency across participants or the robustness of the findings. These limitations concern the available registry information and do not establish what analyses may have been conducted outside the record.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Study of the Inflammation and Airway Changes That Occur After Exposure to Allergen in Asthmatics — NCT02230189.
• Registry record last updated 2022-08-16; status last verified 2022-07.
• Results first posted 2022-08-16.
• 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

NCT02230189 is a completed Phase 2, single-group mechanistic study of airway responses after allergen exposure in people with asthma and other volunteer groups. Enrollment is recorded as 28. The study description includes segmental allergen and diluent challenge, bronchoscopy, and airway epithelial sampling.

The primary endpoint compares change in epithelial miRNA read counts after allergen with change after diluent in participants with allergic asthma, using normalized log2 copy number. The description reports an unadjusted significance threshold of <0.05, but primary outcome estimates and statistical results are not reported in the registry record. The brief summary’s stated total of 38 subjects is not reconciled with the enrollment entry. Safety figures are listed by participant group, with deaths recorded as 0 in each group.