Effect of Roflumilast on Airway Blood Flow as an Expression of Airway Inflammation in COPD: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Effect of Roflumilast on Airway Blood Flow as an Expression of Airway Inflammation in COPD (NCT02097992), a randomized phase 1, phase 2 study. The primary outcome is Airway Blood Flow Reactivity (Delta Qaw).

2. Clinical Question

3. Trial Design

The study is recorded as randomized, triple-masked, and crossover, with phase 1 and phase 2 designations. Its stated enrollment was 11, and its status is completed. The sponsor is the University of Miami. The registry lists a start date of 2013-02 and primary completion date of 2015-07.

A crossover design means treatment comparisons are made across periods in which participants receive different regimens, rather than assigning each participant to remain in a single treatment group throughout. The registry describes sequences that combine a single dose of roflumilast or placebo with subsequent 4 week daily treatment periods. The multi-dose periods are separated by a 4 week washout. The sequences vary whether roflumilast or placebo is used in each period.

The design therefore includes both single-dose and multi-dose questions. The study summary describes assessing the effect of a single dose on airway blood flow in study period 1, and the effect of longer roflumilast treatment on airway blood flow reactivity in study period 2. The primary outcome record, however, gives the timeframe as “Immediate or 4 weeks” without identifying a single time point for a unified treatment comparison.

Randomization and masking are recorded, but the registry record does not report the method used to generate the treatment sequence, how allocation was concealed, or who was masked. It also does not describe the rationale for the enrollment target, adherence to each sequence, or whether the washout was considered sufficient for the treatment effects under study. These design details are not reported in the registry record.

4. Participant Flow and Accounting

The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.

Treatment 1 (1 Day)

Treatment 2 (4 Weeks)

Washout (4 Weeks)

Treatment 3 (4 Weeks)

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 Airway Blood Flow Reactivity (Delta Qaw), measured over Immediate or 4 weeks.

The primary outcome is airway blood flow reactivity, labeled delta Qaw and measured as a percentage of change. The registry describes it as the percentage change in airway blood flow induced by albuterol. The assessment timeframe is listed as immediate or 4 weeks, reflecting the study’s single-dose and multi-dose periods.

Airway blood flow is the quantity being assessed; reactivity describes its change in response to albuterol. A percentage-change measure expresses the response relative to a reference measurement, but the registry record does not specify the exact calculation, the reference value, or the measurement procedures. It also does not report whether the recorded endpoint represents a change from baseline, a contrast between treatment periods, or another summary.

The study description frames airway blood flow as an expression of airway inflammation. In that context, the endpoint was selected to examine whether roflumilast exposure was associated with a change in the airway response to albuterol. The record does not establish that this measure is a validated substitute for other clinical outcomes, nor does it report a numerical primary-outcome estimate or its uncertainty. As a result, the endpoint definition can be described, but the magnitude and precision of any treatment contrast cannot be evaluated from the registry results.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary outcome is a continuous measure: percentage change in airway blood flow induced by albuterol. For a continuous outcome, a treatment comparison commonly summarizes the measured values within each treatment condition and estimates a contrast between conditions. In a crossover study, the analysis may also need to account for the fact that measurements from the same participant are related. The registry record identifies the outcome parameter as a mean and its dispersion as a standard error, but does not report the actual values or the method used to compare treatment conditions.

What does a mean describe?

General explanation: a mean is an average that provides a central summary of observed measurements. It can be useful for describing a continuous outcome, but a mean alone does not show how variable the measurements are or how precisely a treatment contrast has been estimated. The registry lists mean and standard error as the outcome summary, but no numerical mean or standard error is reported for the primary outcome.

How should a standard error be read?

General explanation: a standard error describes the sampling uncertainty of an estimate under the statistical model. It is not the same as the spread of individual observations. A smaller standard error generally indicates a more precise estimate, while a larger one indicates greater uncertainty. The registry names standard error as the dispersion measure for the primary outcome, but gives no numerical value from which to judge precision.

What would a confidence interval add?

General explanation: a confidence interval gives a range of estimates compatible with the observed data and the specified statistical procedure. Its width communicates precision, while its position helps readers assess the direction and plausible magnitude of a contrast. No confidence interval for the primary outcome is reported in the registry record. Therefore, neither the range of plausible treatment contrasts nor their precision can be evaluated.

Why does the crossover structure matter?

General explanation: observations from the same person are usually correlated, so an analysis of crossover data should reflect the within-person structure rather than treating every measurement as independent. Period and sequence can also be relevant features of the design. A washout period is intended to separate treatment periods, but the record does not report how carryover, period effects, or sequence effects were assessed. It also does not describe the statistical model or the assumptions used for the primary comparison.

What do the planning assumptions mean?

The registry describes planning illustrations based on an observed effect, with a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. For non-time-to-event outcomes, those illustrations are expressed as participants per arm; the record’s general description distinguishes this from time-to-event calculations, which use total events. The illustrations consider detecting a stated fraction of the observed effect. These are planning calculations, not observed power and not results from this completed study. They depend on the effect used as their starting point, which is not reported as a numerical primary-outcome estimate in the registry record.

General explanation: over-dispersion occurs when data vary more than a statistical model assumes. If present, it can make model-based uncertainty estimates too small unless the analysis accounts for it. This is a general consideration for statistical modeling, not a reported feature of this trial. The registry record does not report whether over-dispersion was assessed or relevant to the outcome analysis.

Because no primary-outcome analysis results are posted, readers cannot verify the estimated treatment contrast, its uncertainty, the model assumptions, or the handling of repeated measurements. The analysis method, any adjustment for design features, and any sensitivity analyses are not reported in the registry record.

10. Multiplicity, Missing Data and Analysis Populations

The primary outcome is described with the timeframe “Immediate or 4 weeks,” and the registry indicates that it has several categories or time points and was not reduced to one comparison. This matters because results at different time points or for different contrasts can answer distinct questions. If several comparisons are examined, the interpretation of statistical evidence can depend on whether and how multiplicity is addressed. The registry record does not report a multiplicity plan or explain how a primary comparison was selected across the listed timeframes.

The record lists one outcome measure, but that alone does not establish that only one statistical comparison was made. The number of analyses reported is zero, and no primary-outcome estimate is posted. Prespecified secondary analyses, subgroup analyses, or interim analyses are not reported in the registry record. It would therefore be inappropriate to infer how many analyses were planned or whether any adjustment was used.

Missing-data handling is also not described. The record does not report the number of participants with outcome measurements at each time point, reasons for missing measurements, or the method used to handle incomplete crossover data. The analysis population is not specified: the registry record does not say whether the primary analysis included all randomized participants, only those who completed the treatment periods, or another defined population.

These omissions limit assessment of potential bias and reproducibility. In a crossover study, missing measurements from one treatment period may affect the within-person comparison, and the impact depends on why the data are absent and how the analysis handles them. Without information on missingness, analysis populations, and prespecified comparisons, the registry entry does not support a full assessment 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 non-serious adverse event terms

The registry reports serious adverse events, other adverse events, and deaths by exposure group. For the single-dose roflumilast group, 0 serious adverse events, 0 other adverse events, and 0 deaths are recorded among 6 at risk. For the single-dose placebo group, the corresponding counts are 0, 0, and 0 among 5 at risk.

For multi-dose roflumilast, 0 serious adverse events, 1 other adverse event, and 0 deaths are recorded among 11 at risk. For multi-dose placebo, 0 serious adverse events, 2 other adverse events, and 0 deaths are recorded among 11 at risk. No serious adverse event terms are listed.

These are reported counts, not estimates of comparative risk. The record does not provide event descriptions for the other adverse events, their timing, severity, relationship to treatment, or the method used to collect them. In a crossover design, exposure-group counts may reflect treatment periods rather than independent groups of participants; the counts should not be added to produce a total number of affected participants. The entries describe the posted safety information but do not establish that no unreported events occurred.

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

The registry record documents a randomized, triple-masked crossover study of roflumilast and placebo in people with stable COPD who regularly used inhaled corticosteroids. Its primary outcome was airway blood flow reactivity, expressed as percentage change induced by albuterol, with assessments described as immediate or after 4 weeks. The treatment sequences included single-dose and daily multi-dose regimens, with a 4 week washout between multi-dose periods.

What the record does not provide is a numerical primary-outcome result. It does not report the treatment contrast, group or period means, standard errors, confidence intervals, or p values. Therefore, the registry information cannot establish whether the observed airway blood flow response differed between roflumilast and placebo, how large any difference was, or how precisely it was estimated. The completed status is not evidence of a particular outcome.

The safety counts are limited to the recorded adverse-event categories and exposure groups. They show zero recorded serious adverse events and deaths in each group, with other adverse-event counts reported for the multi-dose groups. These figures do not establish comparative safety because the registry does not describe the events, their severity, their relationship to treatment, or the completeness of reporting.

The study’s framing of airway blood flow as an expression of airway inflammation explains the scientific question, but the registry record does not demonstrate that the endpoint predicts broader clinical outcomes. The record also does not report the analysis methods needed to assess how the crossover structure, multiple timeframes, missing data, or analysis population were handled. Conclusions about treatment effects, clinical importance, and statistical certainty therefore cannot be drawn from the posted registry information alone.

13. Why This Trial Matters Statistically

This study is statistically notable for combining a crossover design with both single-dose and multi-dose treatment questions. Crossover designs can support within-participant comparisons, which may be informative when measurements from the same person are related. At the same time, the analysis must account for the structure of repeated observations and possible differences across periods or sequences. The registry identifies the design but does not report how those features were handled statistically.

The primary outcome also has more than one stated assessment timeframe: immediate or 4 weeks. The record flags that the outcome has several categories or time points and was not reduced to one comparison. That makes the choice and reporting of a primary contrast important for interpretation. Without a posted estimate for a defined comparison, readers cannot determine how the study’s different treatment periods and timeframes relate to the scientific question.

The registry’s planning description illustrates a further distinction: calculations based on an observed effect are design illustrations, not observed power and not evidence that an effect was found. The numerical outcome estimate that would anchor those illustrations is not reported in the record, so the planning assumptions cannot be connected to a reported result.

Finally, the registry provides limited safety counts but no primary-outcome analysis. That contrast shows why outcome definition and outcome reporting are both essential: a clear endpoint says what was intended to be measured, while an estimate and its uncertainty are needed to understand what the data indicate. The record makes the study question and broad design visible, but not the statistical result needed to answer that question.

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 of the registry record for interpreting this trial is the absence of numerical primary-outcome results. Although the endpoint and its timeframe are identified, no treatment contrast, mean, standard error, confidence interval, or p value is reported. The record also notes that the primary outcome includes several categories or time points and was not reduced to one comparison, leaving the relevant contrast unclear.

Details needed to evaluate the crossover analysis are not reported in the registry record. These include the statistical model, treatment of within-participant correlation, assessment of period or sequence effects, and evaluation of possible carryover. The record gives the washout duration but does not explain the rationale for it or report whether carryover was assessed.

The record does not describe the primary analysis population, completeness of outcome measurements, missing-data methods, or sensitivity analyses. It also does not report the allocation-generation or concealment procedures, who was masked, or the rationale for the enrollment target. These details would help readers assess the conduct and robustness of the study.

Safety information is limited to event counts by exposure group. Event descriptions, severity, treatment relationship, timing, and collection methods are not reported. Because the design is crossover, the exposure-group counts should not be interpreted as independent participant groups or combined into a total number of affected participants. These limitations concern what the registry record reports; they do not establish that the information was absent from other study materials.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Effect of Roflumilast on Airway Blood Flow as an Expression of Airway Inflammation in COPD — NCT02097992.
• Registry record last updated 2017-11-24; status last verified 2017-10.
• Results first posted 2017-08-18.
• 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 lists NCT02097992 as a completed randomized, triple-masked crossover study in phase 1 and phase 2, sponsored by the University of Miami. It records 11 enrolled participants, with a start date of 2013-02 and primary completion date of 2015-07. The study concerned roflumilast and airway blood flow in COPD.

The primary outcome was airway blood flow reactivity, measured as percentage change induced by albuterol, with an immediate or 4 week timeframe. The described sequences combined single-dose and 4 week daily roflumilast or placebo regimens, with a 4 week washout between multi-dose periods.

The registry reports adverse-event counts by exposure group but does not report a numerical primary-outcome estimate or the analysis details needed to interpret a treatment contrast. Its outcome entry identifies multiple time points or categories without reducing them to one comparison.