Investigate the Impact of Early Treatment Initiation With Tiotropium in Patients Recovering From Hospitalization for an Acute COPD Exacerbation 2: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Investigate the Impact of Early Treatment Initiation With Tiotropium in Patients Recovering From Hospitalization for an Acute COPD Exacerbation 2 (NCT01662986), a randomized phase 4 study. The primary outcome is Change From Baseline of Trough FEV1 at 12 Weeks on Study Drug..

2. Clinical Question

The registry describes a phase 4, randomized, placebo-controlled study in patients recently hospitalized for an acute COPD exacerbation. The clinical question concerns lung function during recovery, rather than a comparison in a general COPD population. Trough FEV1 was measured before the next study-drug dose and approximately 24 hours after the previous inhalation.

The reported group means describe change from baseline; they are not measurements of absolute lung function at week 12. A comparison of changes can help describe how the groups' average lung-function measurements shifted over the study period. It does not, on its own, establish why any shift occurred or how it relates to outcomes such as symptoms or future hospitalization. Those broader clinical questions are not answered by the primary endpoint alone.

3. Trial Design

The registry identifies this as a phase 4, randomized, placebo-controlled, double-blind, parallel-group, multicenter study sponsored by Boehringer Ingelheim. The study is titled “Investigate the Impact of Early Treatment Initiation With Tiotropium in Patients Recovering From Hospitalization for an Acute COPD Exacerbation 2.” The registry lists an enrollment of 79 and a completed status. Its recorded start was 2012-08-01, and its primary completion date was 2014-04-01.

Participants were assigned to daily tiotropium bromide or daily placebo, with both interventions administered as inhalation powder capsules via HandiHaler. In a randomized design, allocation is intended to reduce systematic differences between groups at the point of assignment. Double masking means that the study was described as double-blind; which specific people were masked is not reported in the registry record. The parallel-group model means that the groups received their assigned interventions as separate arms, rather than crossing over between treatments.

The primary outcome was change from baseline in trough FEV1 at 12 weeks on study drug. The primary outcome population is described as the treated set, defined as randomized patients who took at least one dose. The week-12 primary analyses included 29 patients in the placebo group and 30 in the tiotropium group. These analyzed counts are distinct from the registry’s total enrollment. The original sample-size justification, planned allocation counts, and reasons for any difference between enrollment and the analyzed counts are not reported in the registry record.

The registry also lists secondary outcomes, including lung-function measures and clinical events, as well as outcomes combining this study with a twin trial. The specific protocol details governing those analyses, including any prespecified hierarchy among outcomes, 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.

Before assignment: Randomized, placebo-controlled, double blind, parallel group design involving an event-driven treatment period up to the close of the study and a minimum 30-day follow-up period up to the close of the study

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: Treated Set (TS): The treated set included all patients randomized and who took at least one dose of the study drug. The number of patients analyzed at week 12 from the treated set were 29 for Placebo and 30 for Tiotropium.

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: Treated set (TS): The treated set included all patients randomized and who took at least one dose of the study drug.

6. Primary Endpoint

The registry lists the primary outcome as Change From Baseline of Trough FEV1 at 12 Weeks on Study Drug., measured over Baseline and 12 weeks.

The primary endpoint is the mean change from baseline in trough FEV1 at 12 weeks on study drug, measured in litres. FEV1 is the volume of air forcibly exhaled in the first second of a forced expiration. A trough measurement is taken before the next dose; the registry defines this as approximately 24 hours after the last inhalation. The timing is intended to measure lung function near the end of the dosing interval, rather than shortly after a dose.

Change from baseline expresses how the measurement shifted during the study for the analyzed group. Reporting the mean gives the average change, while the standard deviation describes how spread out individual changes were around that average. These are different summaries: the mean describes the central group result, and the standard deviation describes variation among participants.

As a general statistical consideration, a lung-function endpoint offers a measurable way to compare average respiratory function across randomized groups. It is one aspect of COPD and does not itself represent the full range of symptoms, daily function, exacerbations, or hospital use. The registry’s primary endpoint therefore addresses a specific question about average lung-function change over 12 weeks, not every possible consequence of treatment during recovery.

7. Results Posted in the Registry

• Tiotropium Bromide (18 μg): mean 0.19 versus 0.12 on control; difference 0.06 (95% CI -0.13 to 0.26), standardized effect d = 0.16; z-test p = 0.536.

8. Secondary Efficacy Endpoints

The registry also posts results for secondary outcomes. For each outcome below, the endpoint type, the test applied to the posted summary statistics, the result and its interpretation are given in turn. Secondary endpoints are usually not adjusted for multiple testing, so they support rather than confirm the primary finding.

Change From Baseline of Trough FVC at 12 Weeks on Study Drug.

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard deviations.
• Result:
  • Tiotropium Bromide (18 μg): mean 0.28 versus 0.09 on control; difference 0.19 (95% CI -0.05 to 0.44), standardized effect d = 0.39; z-test p = 0.127.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Tiotropium Bromide (18 μg) and the control. The interval gives the range of effects that remain compatible with the data.

Change From Baseline of Trough FEV1 at 12 Weeks on Study Drug From the Two Twin Trials, Present 205.478 (NCT01662986) and 205.477 (NCT01663987)

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard deviations.
• Result:
  • Tiotropium Bromide (18 μg): mean 0.18 versus 0.04 on control; difference 0.15 (95% CI 0.03 to 0.27), standardized effect d = 0.46; z-test p = 0.013.
• Interpretation:
  • The 95% confidence interval excludes no difference, so the mean is statistically higher for Tiotropium Bromide (18 μg) than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.

Change From Baseline of Trough FVC at 12 Weeks From the Two Twin Trials, Present 205.478 (NCT01662986) and 205.477 (NCT01663987)

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard deviations.
• Result:
  • Tiotropium Bromide (18 μg): mean 0.28 versus -0.01 on control; difference 0.29 (95% CI 0.14 to 0.44), standardized effect d = 0.69; z-test p = <0.001.
• Interpretation:
  • The 95% confidence interval excludes no difference, so the mean is statistically higher for Tiotropium Bromide (18 μg) than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.

The secondary outcomes cover additional lung-function measures and clinical events, and the registry also lists outcomes combining this study with its twin trial. The available secondary lung-function summaries show a broadly positive direction for the tiotropium-group mean changes. However, the single-trial FVC comparison has an interval that includes zero, while the listed combined-trial FEV1 and FVC comparisons have intervals that do not include zero. These findings have different scopes: the latter combine results across two trials and do not change the interpretation of the primary endpoint from this trial alone.

The secondary results complement the primary question by examining another lung-function measure and by placing results in the context of a larger combined trial dataset. They do not show that every outcome moved in the same way, nor do they establish a consistent pattern across all secondary outcomes. The registry lists further endpoints involving exacerbations, hospital use, readmission, and adverse events, but numerical results for all listed outcomes are not reported in the registry record.

Unadjusted secondary results generally carry less weight than a prespecified primary result because many outcomes create more opportunities for chance findings. If multiple outcomes or comparisons are tested, the chance of at least one apparently notable result can increase. A multiplicity adjustment or a prespecified testing sequence can address this issue, but the registry record does not report whether either was used. The record also does not identify which secondary outcomes, if any, were intended to be confirmatory.

Accordingly, secondary outcomes can help describe the breadth of the evidence and suggest questions for further study, but they should not be used selectively to override an uncertain primary comparison. Combined-trial summaries are informative about the listed pooled data, yet they answer a different question from the single-trial primary analysis. The analysis plan and multiplicity handling are not reported, so the secondary findings are best interpreted as supportive context rather than definitive confirmation.

Secondary outcomes registered for this trial, for reference (only those above were recalculated):

• Change From Baseline of Trough FVC at 12 Weeks on Study Drug.
• Percentage of Patients With Adverse Clinical Event During on Study.
• Change From Baseline of Trough FEV1 at 12 Weeks on Study Drug From the Two Twin Trials, Present 205.478 (NCT01662986) and 205.477 (NCT01663987)
• Change From Baseline of Trough FVC at 12 Weeks From the Two Twin Trials, Present 205.478 (NCT01662986) and 205.477 (NCT01663987)
• Percentage of Patients With COPD Exacerbation From the Two Twin Trials, Present 205.478 (NCT01662986) and 205.477 (NCT01663987)
• Percentage of Patients With All-cause Hospitalization From the Two Twin Trials, Present 205.478 (NCT01662986) and 205.477 (NCT01663987).
• Percentage of Patients With 30-day Hospital Readmission Rates Outcome Event From the Two Twin Trials, Present 205.478 (NCT01662986) and 205.477 (NCT01663987)
• Number of COPD Exacerbation Events From the Two Twin Trials, Present 205.478 (NCT01662986) and 205.477 (NCT01663987)

9. Statistical Interpretation

10. Statistical Methods Explained

The primary outcome is continuous, measured in litres, and summarized as a mean with a standard deviation. Continuous outcomes can take a range of values rather than falling into categories such as event or no event. The mean condenses the group’s measurements into an average, while the standard deviation indicates how dispersed the participant-level measurements are around that average. A large standard deviation relative to the mean difference suggests that individual results vary considerably around the group average; it does not by itself show whether the estimated group difference is reliable.

The comparison is expressed as a mean difference: the tiotropium group’s average change minus the placebo group’s average change. A positive estimate means the average change was greater in the tiotropium group under this direction of comparison. The primary estimate is 0.062 litres. This is a simple, unadjusted comparison based on the posted summary statistics, not a reported covariate-adjusted model. The registry record does not report a sponsor analysis for this comparison, nor does it describe an adjusted statistical model.

A confidence interval gives a range of values compatible with the observed estimate under the method’s assumptions. It communicates uncertainty about the group difference rather than a range containing a guaranteed proportion of individual participant results. For the primary estimate, the interval includes zero. Consequently, the posted summary statistics do not precisely distinguish the estimated difference from no difference. The registry record does not specify the confidence level for the interval, so no confidence level is assigned in this explanation.

The unadjusted p-value for the primary comparison is 0.536. In general, a p-value describes how unusual data at least as inconsistent with a null hypothesis would be if that hypothesis and the model assumptions were true. It is not the probability that the null hypothesis is true, and it does not measure the clinical importance of the estimate. The p-value should be read alongside the estimate and its interval, rather than treated as a stand-alone verdict. The registry record does not report whether the p-value is part of a prespecified testing hierarchy or whether an adjustment for multiple testing was planned.

Randomization and masking concern different parts of trial conduct. Random assignment is intended to make treatment groups comparable on average at assignment, including for factors not measured or reported. Masking is intended to limit the influence of knowledge of assigned treatment on care, assessment, or reporting. The registry identifies the study as randomized and double-blind, but further details about implementation, concealment, and which parties were masked are not reported in the registry record. These design labels do not eliminate uncertainty from small analyzed groups, missing measurements, or limitations in the analysis description.

The primary analysis population is the treated set. It includes all randomized patients who took at least one dose, according to the registry definition. The number analyzed at week 12 was 29 for placebo and 30 for tiotropium. This is not the same description as an analysis of every randomized participant regardless of whether they began treatment. The registry record does not report a separate intention-to-treat analysis, the number of missing week-12 measurements, or the method used to address missing data. It is therefore not possible to determine from the record whether missingness could have affected the group summaries.

Standard deviations and confidence intervals answer different questions. The standard deviation summarizes participant-to-participant variation within a group. The confidence interval summarizes uncertainty about a group-level estimate, such as a mean difference. A narrow interval would indicate greater precision under the calculation’s assumptions; a wide interval indicates that a broader range of differences remains compatible with the data. The primary interval spans zero, reflecting substantial uncertainty about the direction and size of the difference.

Over-dispersion is a general issue for count outcomes: observed event counts may vary more than a simple model expects. It can make standard errors and confidence intervals too small if the model does not account for the extra variation. The primary endpoint is continuous rather than a count, so that particular count-data concern is not the central issue for the primary comparison. The registry lists count and event-related secondary outcomes, but the statistical methods used for those outcomes are not reported in the registry record.

The record lists secondary endpoints and outcomes combining the two twin trials. It does not report the analysis models for those endpoints or whether estimates were adjusted for baseline measurements, study site, or other factors. The pooled secondary results are therefore described as posted group summaries and simple unadjusted comparisons where such comparisons are presented, rather than being attributed to an undocumented model. The record does not report a statistical analysis plan, interim analyses, or a multiplicity strategy. These omissions limit the ability to distinguish planned confirmatory analyses from exploratory analyses.

The planning illustrations use the observed effect as a reference and calculate participant counts under stated assumptions. In general, power is the probability that a specified statistical procedure will detect an effect of a chosen size under its assumptions. A planning calculation asks how many participants would be needed for a target power and chosen effect; it does not measure the power actually achieved by the completed trial. The original design assumptions for this trial, including its intended effect size and sample-size justification, are not reported in the registry record.

11. Confidence Intervals and Precision

Precision concerns how narrowly the data estimate the between-group difference. The primary mean difference is 0.062 litres, and its confidence interval includes zero. The interval therefore leaves uncertainty about whether the underlying average difference is positive, close to zero, or negative. The estimated direction alone should not be read as a precise estimate of the underlying difference.

The uncertainty is consistent with the size of the analyzed groups and the observed spread in measurements. At week 12, the primary treated-set analysis included 29 placebo recipients and 30 tiotropium recipients. The standard deviations were 0.271 litres and 0.475 litres, respectively. These values describe substantial participant-level variability around the group means, particularly in the tiotropium group. A mean difference can be estimated even when individual measurements vary widely, but that variability affects how precisely the group contrast can be estimated.

The interval is a measure of uncertainty in the estimated difference, not a prediction interval for individual participants. It does not show where most individual changes fell, and it does not imply that the true difference has a particular probability of lying within the interval. Its interpretation depends on the statistical method and its assumptions. The registry record does not report the confidence level or the analysis model for the interval.

The primary result should therefore be read as an imprecise estimate rather than as evidence that the groups are identical. At the same time, the observed difference should not be treated as a precise estimate of a treatment effect. The interval’s inclusion of zero and the unadjusted p-value of 0.536 reflect that the primary data do not sharply separate the estimated group difference from no difference under the reported calculation.

12. Planning a Similar Trial: Sample Size

This is a planning illustration, not a re-evaluation of the original trial. It asks: if a new study wanted to detect a difference like the one observed, or a smaller one, how large would it need to be? It is deliberately not “observed power” of the finished trial, which is not a meaningful quantity.

The planning figures are illustrations based on the observed effect, not a record of the trial’s original design target. They assume a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. The effect to detect is set to a stated fraction of the observed effect. For these continuous outcomes, the figures are participants per arm, not total participants and not total events. The original trial’s sample-size assumptions and justification are not reported in the registry record.

The 80% power column gives the number of participants per arm estimated to be needed, under those assumptions, for an 80% chance of detecting the chosen effect if that effect were the true one and the model assumptions held. The 90% power column gives the corresponding planning count for a 90% chance. These are hypothetical planning probabilities for a future study, not a description of the chance that the completed study found a true result.

The rows express planning for 100%, 75%, and 50% of the observed effect. A smaller effect is harder to distinguish from random variation, so planning to detect a smaller effect requires more participants. This pattern is reflected in the figures. The estimates depend on the observed effect used as a starting point; if that estimate is imprecise, the resulting planning illustrations are also uncertain. They should not be treated as a definitive sample-size recommendation.

These counts are not observed power. Observed power calculated from the completed study’s result would largely re-express the p-value and would not resolve uncertainty about the effect. The planning figures instead show how the required sample can change with the assumed effect size and target power. They do not reconstruct the sponsor’s original design process.

13. How the Sample Size Is Derived

Power is the probability that a study of a given size rejects the null hypothesis when a specific true effect exists. It depends on four things: the effect to detect, the variability of the outcome, the significance level (here a two-sided α of 0.05, so z_1−α/2 = 1.960) and the desired power (z_1−β = 0.842 for 80% and 1.282 for 90%).

Formula

n is the number of participants in each arm, Δ is the difference in means to detect and σ is the common standard deviation.

Worked calculation for this trial

1. Observed difference Δ = 0.062; pooled standard deviation σ = 0.388.
2. n = 2 × (1.96 + 0.842)² × 0.388² / 0.062² = 616.1, rounded up to 617 participants per arm for 80% power.

The smaller-effect rows in the table above repeat the same calculation with the effect multiplied by 0.75 and 0.5 (for ratios, applied to the logarithm of the ratio).

R code

alpha <- 0.05
z_a   <- qnorm(1 - alpha / 2)          # two-sided
delta <- 0.062                      # observed difference in means
sigma <- 0.388417233614088                     # pooled standard deviation
n_per_arm <- function(power, frac = 1) {
  ceiling(round(2 * (z_a + qnorm(power))^2 * sigma^2 / (delta * frac)^2, 6))
}
for (f in c(1, 0.75, 0.5))
  cat(sprintf("%3.0f%% of observed effect: n per arm = %s (80%% power), %s (90%% power)\n", 100 * f,
              format(n_per_arm(0.80, f), big.mark = ","), format(n_per_arm(0.90, f), big.mark = ",")))

# Check against R's built-in function (t-based, so very slightly larger)
cat("power.t.test:", round(power.t.test(delta = delta, sd = sigma, power = 0.80)$n, 1), "\n")

# Simulation: exact two-sample t-test using simulated means and variances
set.seed(1662986)
n    <- n_per_arm(0.80)
reps <- 20000
m_diff <- rnorm(reps, delta, sigma * sqrt(2 / n))             # difference in sample means
s2     <- sigma^2 * rchisq(reps, 2 * (n - 1)) / (2 * (n - 1))   # pooled sample variance
tstat  <- m_diff / sqrt(s2 * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(tstat) > qt(0.975, 2 * (n - 1))), reps))

Output from running the code

100% of observed effect: n per arm = 617 (80% power), 825 (90% power)
 75% of observed effect: n per arm = 1,096 (80% power), 1,467 (90% power)
 50% of observed effect: n per arm = 2,465 (80% power), 3,300 (90% power)
power.t.test: 617.1 
Simulated power at n = 617 per arm: 0.800 (20000 replicates)

The simulation draws many sets of group means and variances at the planned sample size and counts how often the two-sample t-test rejects the null. It should land close to the target power; at very small required sample sizes it can fall below it, because the normal approximation is rough there.

14. Multiplicity, Missing Data and Analysis Populations

The registry lists multiple outcome measures, including a primary endpoint and secondary measures. Testing several outcomes can increase the chance that at least one result appears notable by chance alone. Statistical approaches can account for this multiplicity, for example by adjusting significance thresholds or by specifying an ordered testing strategy. Whether such a strategy was planned or used is not reported in the registry record. The record also does not report interim analyses or a statistical analysis plan.

Missing outcome data can affect a group comparison if the availability of measurements is related to participants’ outcomes or treatment assignment. The primary outcome population is described as the treated set: randomized patients who took at least one dose. The registry reports 29 placebo participants and 30 tiotropium participants analyzed at week 12 for the primary endpoint, against total enrollment of 79. The number of missing week-12 values, reasons for missingness, and methods for handling missing observations are not reported in the registry record. The difference between enrollment and these analysis counts cannot be attributed to any particular reason from the record.

The registry’s treated-set definition is not equivalent to an analysis of all randomized participants regardless of treatment initiation. Whether an intention-to-treat analysis was performed, and whether it agreed with the treated-set results, is not reported in the registry record. The record does not report sensitivity analyses addressing missing data or analyses using alternative populations.

These limitations matter because the group summaries depend on who contributed outcome data and on how unobserved values were handled. They do not prove that the results are biased, but they prevent a full assessment of robustness. The registry also does not report the original sample-size justification or the details needed to assess whether the final analysis followed a prespecified plan.

15. 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 5% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: chronic obstructive pulmonary disease (17.9%), leukocytosis (2.6%), hypothyroidism (2.6%), abdominal pain (2.6%), melaena (2.6%).

The registry reports serious adverse events affecting 9 of 39 participants at risk in the placebo group and 10 of 39 at risk in the tiotropium group. It reports other adverse events affecting 11 of 39 placebo participants and 23 of 39 tiotropium participants. These are counts of participants recorded as affected, not estimates of causal effects. The record does not provide an adjusted comparison or establish that an event was caused by study treatment.

The most frequently listed serious adverse-event term was chronic obstructive pulmonary disease, reported as 17.9%. Leukocytosis, hypothyroidism, abdominal pain, melaena, and upper gastrointestinal haemorrhage were each listed as 2.6%. The registry’s adverse-event summary should be read as a record of reported events, not as a complete comparison of the likelihood or severity of all possible harms.

Death counts are not reported in the registry record. The available counts do not explain event timing, duration, severity beyond the serious-event classification, or individual participants’ clinical circumstances. Differences in counts between groups should therefore be treated descriptively, without inferring a treatment-related cause.

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

The primary result describes average change in trough FEV1 over 12 weeks among participants in the treated-set analysis. The tiotropium group had a larger mean increase than the placebo group, with an unadjusted difference of 0.062 litres. The confidence interval includes zero, and the unadjusted p-value was 0.536. Taken together, these results indicate substantial uncertainty about the size and direction of the underlying between-group difference.

The result does not establish that the groups were identical. A non-significant p-value is not proof of no difference, and an interval that includes zero can still contain nonzero differences. Nor does the positive point estimate establish that tiotropium caused the observed difference. The estimate is based on a limited number of week-12 observations, and the registry does not report the missing-data methods or a detailed analysis plan.

The primary endpoint is one measure of lung function and does not encompass all aspects of recovery from an acute COPD exacerbation. The secondary outcomes include other lung-function measures and clinical-event measures, but their interpretation is limited by incomplete posted numerical results and the absence of reported multiplicity methods. The combined-trial secondary summaries should be distinguished from the result for this trial alone.

The safety counts are descriptive. They document adverse events recorded in each group but do not, by themselves, identify causation or establish comparative safety. The registry record also does not report death counts. Together, the efficacy and safety summaries should be interpreted as evidence about the measured outcomes and recorded events in the analyzed groups, not as a comprehensive account of all possible benefits or harms.

In general, trial results are most informative when estimates, uncertainty, analysis populations, missing-data handling, and prespecified methods can all be evaluated together. Some of those details are not reported in the registry record. The posted data therefore support a careful description of the observed averages and event counts, while leaving important questions about precision and analysis conduct unresolved.

17. Why This Trial Matters Statistically

This study is statistically notable because it asks a focused question in a specific recovery setting: whether average trough lung-function change differed between randomized groups after hospitalization for an acute COPD exacerbation. The placebo comparison, randomization, and double-blind design are relevant features for interpreting group contrasts, while the treated-set outcome population and week-12 analysis counts define who contributed to the primary result.

The primary estimate illustrates why an effect estimate should be read together with its uncertainty. The tiotropium group’s mean change was numerically larger, but the confidence interval includes zero and the unadjusted p-value is 0.536. The point estimate alone would give an incomplete account; the interval and analyzed sample sizes show that the comparison is not precise enough to sharply distinguish a difference from no difference.

The registry also lists outcomes from two twin trials, which allows a broader combined-trial view for selected secondary measures. This illustrates how pooled evidence can differ in precision from a single trial, while also underscoring that a combined secondary analysis is not interchangeable with a trial’s primary result. Clear reporting of the analysis plan, population, and multiplicity handling is needed to understand how such results were selected and interpreted.

Finally, the planning illustrations demonstrate how required sample size depends on the effect a future study aims to detect. They are not evidence that the completed study was adequately powered, and they do not disclose the original design rationale. The registry record leaves that rationale and several analysis details unreported, making transparent uncertainty an important part of the statistical interpretation.

18. 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 comparison is based on 29 placebo participants and 30 tiotropium participants at week 12. These analyzed groups are small enough that estimates can be sensitive to variation among participants, as reflected by the reported standard deviations. The confidence interval around the mean difference includes zero, so the primary estimate is imprecise.

The analysis population is the treated set, not an explicitly reported analysis of all randomized participants regardless of treatment initiation. The registry record does not describe the number or reasons for missing week-12 measurements, how missing data were handled, or whether sensitivity analyses were performed. As a result, the robustness of the primary result to missing outcomes cannot be assessed from the record.

The registry does not report a detailed statistical analysis plan, the original sample-size justification, interim analyses, or a multiplicity strategy. It also does not identify the model used for the primary comparison or provide a confidence level for the reported interval. These gaps limit evaluation of whether the reported analyses followed prespecified methods and how uncertainty was calculated.

The primary endpoint is a lung-function measure over 12 weeks. It does not by itself describe longer-term outcomes or the full range of recovery experiences. Several listed secondary outcomes concern clinical events, but numerical results for all listed measures are not reported in the registry record. The safety summary does not report death counts or enough detail to establish event causation. These limitations narrow what can be concluded from the posted summaries without implying that unreported information had any particular result.

19. Related Tutorials

20. Related Statistical Calculators

21. Sources

• ClinicalTrials.gov: Investigate the Impact of Early Treatment Initiation With Tiotropium in Patients Recovering From Hospitalization for an Acute COPD Exacerbation 2 — NCT01662986.
• Registry record last updated 2018-10-17; status last verified 2018-09.
• Results first posted 2015-07-20.
• 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.

22. Record Summary

The registry describes a completed phase 4, randomized, placebo-controlled, double-blind, parallel-group study of tiotropium bromide 18 μg versus placebo in patients recovering from hospitalization for an acute COPD exacerbation. Total enrollment was 79. The primary endpoint was mean change from baseline in trough FEV1 at 12 weeks on study drug, analyzed in the treated set.

The week-12 mean changes were 0.124 litres with placebo and 0.186 litres with tiotropium. The simple unadjusted difference was 0.062 litres; its confidence interval included zero, and the unadjusted p-value was 0.536. Secondary and combined-trial outcomes provide additional context, but multiplicity handling and several analysis details are not reported in the registry record. The safety counts are descriptive and do not establish causation.