Tiotropium/Salmeterol Inhalation Powder in COPD: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Tiotropium/Salmeterol Inhalation Powder in COPD (NCT00668772), a randomized phase 3 study. The primary outcome is Change From Baseline in Trough Forced Expiratory Volume in One Second (FEV1) at the End of the 12-week Treatment Period.

2. Clinical Question

In practical statistical terms, the central question is whether the recorded lung-function measure differed across the treatment groups at the specified assessment. FEV1 is an objective spirometric measure, and the endpoint uses the pre-dose clinic measurement described in the registry. However, the posted primary outcome does not include a reported treatment-effect estimate or interval comparing the combination with placebo, or with either single-drug group. The tables and plots present the available group summaries and the secondary comparisons that can be displayed from the posted data; those summaries should not be mistaken for a complete account of the trial’s planned analyses.

3. Trial Design

This was a phase 3, randomized, triple-masked, parallel-group study in people with COPD. The registry lists enrollment of 207. The official title describes a placebo-controlled study with placebo control only during the first 12-week period, followed by a planned 24-week treatment period and a 24-week extension. The registry status is terminated. A reason for termination is not reported in the registry record.

The listed groups were fixed-dose combination tiotropium/salmeterol, tiotropium, salmeterol, fixed-dose combination tiotropium/salmeterol plus salmeterol, and placebo. The placebo group was scheduled for 12 weeks, after which participants were to be reassigned at random to one of the treatment groups. The precise allocation ratio and details of the reassignment process are not reported in the registry record. The fixed-dose combination was described as one inhalation-powder capsule administered once daily in the morning. The descriptions of some other regimens are truncated in the registry record, so their full administration schedules cannot be reconstructed.

The primary endpoint was assessed at week 12, although the official title describes a longer study and extension. The primary outcome summaries include 6 participants in the combination group, 6 in the tiotropium group, 9 in the salmeterol group, 11 in the combination-plus-salmeterol group, and 8 in the placebo group. These are the posted outcome-specific sample sizes, not the overall enrollment. The registry lists 50 outcome measures and 41 posted secondary outcomes, but lists no reported analyses for the secondary endpoints. The stated primary objectives cover lung function, dyspnoea, health status, and COPD exacerbations; outcome data for every stated objective are not available in the results.

The record gives study start and primary-completion dates, but those dates do not establish how long each participant was observed or whether the planned extension was completed. The record’s terminated status and the posted week-12 summaries are important context when reading the trial results.

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.

Before assignment: All subjects were screened for eligibility prior to participation in the trial. Subjects attended a specialist site which ensured that they (the subjects) strictly met all inclusion and none of the exclusion criteria. Subjects were not to be allocated to a treatment group if any of the entry criteria were violated.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: Full Analysis Set (FAS): The intent-to-treat (ITT) principle was used to include as many participants as possible in the efficacy analyses. The full analysis set (FAS) consisted of all participants where baseline data and any on-treatment efficacy data were available. This definition was applied separately for each endpoint, so that the number of participants in the analysis may vary across endpoints.

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: The treated set (TS): The treated set consists of all randomised patients who took at least one dose of study medication.

6. Primary Endpoint

The registry lists the primary outcome as Change From Baseline in Trough Forced Expiratory Volume in One Second (FEV1) at the End of the 12-week Treatment Period, measured over At baseline and week 12.

The primary endpoint is change from baseline in trough FEV1 at the end of the 12-week treatment period, measured in litres. FEV1 is the maximal amount of air that can be forcefully exhaled in one second and is measured with a spirometer. Trough FEV1 is defined in the registry as the pre-dose clinic measurement taken at the -10 minutes time point, just before the morning dose of randomized treatment. The reported response is calculated as the trough FEV1 measurement minus baseline FEV1.

This endpoint is used to summarize a treatment-period change in lung function at a standardized time relative to dosing. A pre-dose measurement can describe lung function near the end of the dosing interval, rather than the response immediately after inhalation. That is a general interpretation of the measurement timing, not evidence about a treatment effect in this study.

The registry reports means and standard deviations for the primary outcome by group. It does not provide an estimable two-arm comparison for this endpoint in the displayed results. Consequently, the group summaries alone do not quantify the uncertainty around a treatment contrast, and they do not establish whether observed differences between group means are compatible with chance variation. The outcome-specific sample sizes are small, and the record does not report a primary-effect confidence interval or a sponsor-reported inferential analysis in the available results.

The endpoint is one part of the broader clinical assessment described in the record. The stated objectives also included dyspnoea, health status, and COPD exacerbations. A lung-function measure does not by itself summarize those other outcomes, and their presence in the objectives does not imply that complete results for them are available.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary outcome is continuous, and the registry identifies the reported statistic as a mean with standard deviation. A mean summarizes the central value of the measurements in a group. The standard deviation describes their spread around that group mean; it is not the uncertainty interval for a comparison between groups. Because the posted primary summaries do not support a two-arm comparison, they do not yield a primary treatment-effect confidence interval or p-value in the results.

How to read a mean difference

For the secondary comparisons, a mean difference describes the estimated difference between the treatment-group mean and the placebo-group mean for the listed endpoint. The sign indicates which group has the higher numerical mean under the comparison’s stated ordering. The estimate should be read together with its confidence interval: the interval gives a range of values compatible with the data and the calculation’s assumptions. It is not a guarantee that the true value falls inside that range. The confidence intervals shown for the secondary comparisons are unadjusted, and they do not account for examining multiple endpoints or multiple treatment groups.

For example, the posted comparison for the fixed-dose combination versus placebo on FEV1 area under the concentration-time curve has a mean difference of 0.218 litres, with a 95% confidence interval from -0.053 to 0.489 and an unadjusted p-value of 0.115. This is a secondary comparison, not the primary week-12 trough FEV1 result. Its interval includes zero, so the data are compatible with a range of possible differences, including no difference, under the comparison method. The corresponding tiotropium comparison has a mean difference of 0.163 litres, a confidence interval from -0.113 to 0.439, and an unadjusted p-value of 0.247. These values should not be treated as sponsor-reported analyses: the registry lists no reported analyses for these secondary outcomes.

Why the estimates are imprecise

Precision depends on the amount of information available and the variability in the measurements. In general, smaller groups and more variable outcomes produce less precise estimates, which often appear as wider confidence intervals. The secondary comparison groups include 25 to 28 participants per group, while the primary outcome summaries include substantially smaller outcome-specific groups. This helps explain why the primary summaries alone do not provide a stable basis for a treatment contrast. It does not identify why the outcome-specific samples are smaller than overall enrollment; that reason is not reported in the registry record.

Standard deviations and standard errors answer different questions. A standard deviation describes variation among individual measurements. A standard error describes uncertainty in an estimated quantity, such as a group mean, under a statistical model. The posted secondary comparisons include standard errors and pooled standard deviations alongside estimates. These are part of the calculation record, but they do not reveal whether the trial’s original analysis used covariate adjustment, repeated-measures modeling, or another approach. The registry record does not report those analysis details.

Nominal p-values and multiplicity

A p-value summarizes how incompatible the observed result is with a specified null model, assuming that model and the analysis are appropriate. It is not the probability that the null hypothesis is true, and it does not measure the size or clinical importance of an effect. The listed secondary p-values are explicitly unadjusted. When many outcomes, assessment times, or treatment contrasts are examined, some nominally small p-values can occur by chance even if there are no underlying differences. A prespecified multiplicity procedure can address this issue, but such a procedure is not reported in the registry record. The p-values therefore should be considered exploratory rather than interpreted as a family of confirmatory tests.

Planning illustrations

The sample-size section accompanying the tables gives planning illustrations based on observed effects. These are not observed power calculations and do not describe the trial’s original design. They assume a two-sided significance level of 0.05, equal allocation between two groups, and a normal approximation; the planned effect is a stated fraction of the observed effect. For example, the planning table for the fixed-dose combination versus placebo on the FEV1 area-under-the-curve outcome lists 86 participants per arm for 80% power when planning for 100% of the observed effect, and 152 participants per arm when planning for 75% of that effect. Such figures illustrate how sample-size requirements change with the effect size being targeted. They do not establish that the trial was designed with those assumptions, nor do they estimate the probability that this trial detected a true effect.

Observed effects used in planning can be unstable, particularly when estimated in small groups. Planning illustrations based on those estimates should therefore not be used as evidence that a future study will reproduce the same effect. The sample-size justification and original statistical plan are not reported in the registry record.

Outcome populations and analysis transparency

The primary outcome description defines the Full Analysis Set as including participants with baseline data and any on-treatment efficacy data, applying the intention-to-treat principle as far as possible. The available text does not fully describe how this definition was applied across every endpoint. The record does not report the reasons for missing outcomes, how missing values were handled, or whether sensitivity analyses were conducted. Those omissions matter because the analyzed participants may differ from all randomized participants when outcome data are unavailable. Without the missing-data details and the full analysis plan, the posted group summaries cannot be used to determine how robust the findings are to alternative assumptions.

10. Confidence Intervals for Each Arm

No two-arm comparison is shown for this trial, but each arm's mean can be given with a t-based 95% confidence interval computed from the posted mean, spread and number of participants.

R code and output

arm <- c("FDC Tiotropium / Salmeterol (T+S_PE)", "Tiotropium (Tio18GEL)", "Salmeterol (Salm25PE)", "FDC Tiotropium / Salmeterol + Salmeterol (T+S_PE /", "Placebo")
n   <- c(6, 6, 9, 11, 8)
m   <- c(1.412, 1.48, 1.413, 1.584, 1.031)
sp  <- c(0.317, 0.39, 0.408, 0.542, 0.391)
sd  <- sp      # posted standard deviations
for (i in seq_along(n)) {
  se <- sd[i] / sqrt(n[i]); h <- qt(0.975, n[i] - 1) * se
  cat(sprintf("CARM|%s|%d|%.3f|%.3f|%.3f|%.3f\n", arm[i], n[i], m[i], sd[i], m[i] - h, m[i] + h))
}

CARM  FDC Tiotropium / Salmeterol (T+S_PE)  6  1.412  0.317  1.079  1.745
CARM  Tiotropium (Tio18GEL)  6  1.480  0.390  1.071  1.889
CARM  Salmeterol (Salm25PE)  9  1.413  0.408  1.099  1.727
CARM  FDC Tiotropium / Salmeterol + Salmeterol (T+S_PE /  11  1.584  0.542  1.220  1.948
CARM  Placebo  8  1.031  0.391  0.704  1.358

11. Multiplicity, Missing Data and Analysis Populations

The registry record does not report a multiplicity adjustment or a hierarchy specifying which secondary outcomes or treatment comparisons were intended to support confirmatory conclusions. This is important because the record lists 50 outcome measures and 41 posted secondary outcomes, with results spanning different measures and assessment times. When many statistical comparisons are examined, the chance of at least one nominally small p-value increases. A multiplicity adjustment or a prespecified testing sequence can help control that risk, but the available record does not say whether either was used.

The displayed secondary p-values are unadjusted. They should therefore be read as nominal results for their individual comparisons, not as evidence that the whole set of outcomes meets a single confirmatory standard. The registry also lists no reported analyses for the secondary outcomes. The exact model, covariates, analysis population, and handling of repeated measurements are not reported in the registry record. Without those details, it is not possible to determine whether the posted summaries match the trial’s original analysis plan or to compare them with any sponsor analysis.

The primary outcome population is described as the Full Analysis Set, using an intention-to-treat principle to include as many participants as possible with baseline and on-treatment efficacy data. The complete operational definition is not available in the record. Reasons for missing outcome data, the extent of missingness by group, and the method used to address missing values are not reported in the registry record. No sensitivity analyses for missing data are reported. If outcome availability depends on participants’ health, treatment, or response, an analysis limited to observed outcomes may not represent all randomized participants; this is a general concern, not a claim that such bias occurred.

The primary result presents small outcome-specific groups, but the record does not explain why the available primary samples are smaller than overall enrollment. It also does not report a sample-size justification, an interim-analysis plan, or a statistical analysis plan. The posted planning illustrations are based on observed effects and are not the original trial design rationale. Taken together, these reporting gaps constrain evaluation of both the error rates and the robustness of the posted findings.

12. 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 5% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: anaemia (2.4%), pulmonary tuberculosis (2.2%), haemoptysis (2.2%).

The registry reports serious and other adverse-event counts for each listed group, with separate numbers at risk and affected. For serious adverse events, the counts are 1 of 41 in the fixed-dose combination group, 0 of 43 in the tiotropium group, 1 of 45 in the salmeterol group, 0 of 43 in the combination-plus-salmeterol group, and 0 of 43 in the placebo group. The listed death count is 0 in each group. These are counts from the registry record; they are not adjusted comparisons, and they do not establish that the groups had equivalent safety.

For other adverse events, the affected counts are 3 of 41, 7 of 43, 5 of 45, 6 of 43, and 3 of 43, respectively, in the same group order. The table should be read as a summary of reported events among participants at risk, not as a complete account of event type, timing, duration, or severity. The registry also lists anaemia at 2.4%, pulmonary tuberculosis at 2.2%, and haemoptysis at 2.2% among the serious adverse-event terms. The record does not make the group attribution for those listed percentages clear in the available summary.

These safety summaries have limited interpretability alongside a terminated trial and outcome-specific samples that vary by endpoint. The reason for termination, detailed event narratives, and a formal between-group safety analysis are not reported in the registry record. The counts therefore describe what is posted but cannot establish comparative safety or rule out uncommon harms.

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

The results show that the registry contains group means and standard deviations for change in trough FEV1 at week 12, together with several secondary outcome summaries. They do not provide an estimable primary two-arm treatment comparison in the results. That distinction matters: a list of group averages describes observed measurements, whereas a treatment-effect estimate with a confidence interval quantifies the contrast and its uncertainty. The primary summaries alone cannot answer how precisely the treatment groups differed.

The secondary comparisons provide some contrasts with confidence intervals and unadjusted p-values, but they are not a substitute for the missing primary comparison. The displayed results differ across endpoints, and their inferential weight is limited by the absence of a reported multiplicity strategy and complete analysis details. These data do not establish that one regimen is superior, that regimens are equivalent, or that any observed difference is clinically important. A nominal p-value is not a measure of clinical value, and statistical uncertainty is not resolved by comparing group means alone.

The posted information also does not show the complete results for all objectives described in the trial summary. The record’s terminated status does not explain whether the planned follow-up or extension was completed, and the reason for termination is not reported in the registry record. Missing-data handling, original sample-size justification, and a complete statistical analysis plan are also not reported. These limitations make it difficult to assess the intended confirmatory analysis or the representativeness of the analyzed participants.

In general, a clinical trial result is most informative when the primary comparison, uncertainty interval, analysis population, and handling of missing data are transparent and aligned with a prespecified plan. Here, the available results allow a descriptive account of the posted measurements and a cautious reading of selected secondary contrasts. They do not support a definitive treatment-effect conclusion or a complete benefit-risk assessment. The tables and plots should therefore be read as a record of the available data, not as an independent clinical recommendation.

14. Why This Trial Matters Statistically

This trial is statistically notable for the gap between its broad stated objectives and the information available for its primary endpoint. The record identifies a week-12 trough FEV1 outcome and provides group means, standard deviations, and outcome-specific sample sizes, but the primary comparison is not estimable in the posted results. This illustrates why descriptive summaries and comparative inference are different: the observed means alone do not provide an uncertainty interval for the treatment contrast.

The study also has multiple active-treatment groups, a placebo period limited to the first 12 weeks, and a planned extension described in the official title. That structure raises questions about which comparisons and time points were intended to be central, and how the extension related to the primary assessment. Those protocol and analysis details are not reported in the registry record. Without them, readers cannot fully reconstruct the intended statistical testing strategy from the outcome list.

The secondary data show why multiplicity and transparency matter. There are numerous listed outcomes and time points, while the displayed comparisons are unadjusted and no reported analyses are listed for those secondary endpoints. Individual results can be useful descriptively, but their interpretation depends on whether they were prespecified and how the family of comparisons was handled. The registry does not report that context.

Finally, the outcome-specific samples are small relative to the overall enrollment, and the record does not explain the difference. This limits precision and leaves questions about missingness and analysis populations unanswered. The trial is therefore a useful example of how a registry can contain substantial descriptive information yet still leave core inferential questions unresolved. The most important statistical lesson is not a treatment conclusion, but the need to distinguish posted group summaries from a transparent, prespecified comparison with uncertainty.

15. 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 limitations are specific to the record and results available for this trial. First, the primary endpoint is presented as group means and standard deviations, but a two-arm comparison is not estimable from the posted values. The primary treatment effect, its confidence interval, and its inferential test are therefore unavailable in the displayed results. This prevents a direct assessment of the primary question from the posted summaries.

Second, the outcome-specific sample sizes are small for the primary endpoint and differ between groups. The registry does not explain why the analyzed numbers are smaller than the overall enrollment of 207, or whether this reflects missing measurements, analysis-population rules, or another cause. The record describes a Full Analysis Set based on baseline and on-treatment efficacy data, but the complete population definition and its application across endpoints are not reported.

Third, the study was terminated, but the reason is not reported in the registry record. The official title describes a 24-week period plus a 24-week extension, while the primary result is at week 12; the available record does not establish whether later follow-up was completed. The placebo group was described as receiving placebo only for the first 12 weeks and then being reassigned at random, which further means later comparisons may not have the same placebo reference as the primary-period comparison.

Fourth, the full statistical analysis plan, sample-size justification, missing-data methods, interim-analysis details, multiplicity procedures, and sponsor-reported analyses for the displayed secondary endpoints are not reported in the registry record. The secondary comparisons are unadjusted and cover only a portion of the listed outcomes. Some intervention descriptions are truncated, and the attribution of the listed serious-event percentages is unclear in the available summary. These limitations constrain interpretation of efficacy patterns, safety summaries, and the degree to which the posted results reflect the original analysis plan.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Tiotropium/Salmeterol Inhalation Powder in COPD — NCT00668772.
• Registry record last updated 2026-07-16; status last verified 2026-06.
• Results first posted 2026-07-16.
• 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.

19. Record Summary

The registry record describes a phase 3, randomized, triple-masked, parallel-group COPD trial with enrollment of 207 and status listed as terminated. It compares fixed-dose tiotropium/salmeterol, tiotropium, salmeterol, the combination plus salmeterol, and placebo. Placebo was used only during the first 12-week period, with reassignment planned afterward. The primary endpoint is change from baseline in trough FEV1 at week 12.

The posted primary results give group means and standard deviations, but do not support an estimable two-arm comparison in the displayed data. Selected secondary outcomes include unadjusted comparisons; the registry lists no reported analyses for those secondary endpoints. The record does not report the termination reason, full analysis plan, sample-size justification, or missing-data methods. The available results are best read as descriptive summaries with limited comparative inference.