Investigation of the 24 Hour Forced Expiratory Flow in 1 Second (FEV1) Profile of a Single Dose of Indacaterol/Mometasone Delivered Via the TWISTHALER® Device in Adult Patients With Persistent Asthma: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Investigation of the 24 Hour Forced Expiratory Flow in 1 Second (FEV1) Profile of a Single Dose of Indacaterol/Mometasone Delivered Via the TWISTHALER® Device in Adult Patients With Persistent Asthma (NCT00557440), a randomized phase 2 study. The primary outcome is Change From Period Baseline to 24 Hour Post-dose (Trough) Forced Expiratory Volume in 1 Second (FEV1).

2. Clinical Question

3. Trial Design

This was a Phase 2, randomized, quadruple-masked, double-blind, double-dummy, crossover study with placebo and active control. Novartis was the sponsor. The condition was asthma, and the target population was adults with persistent asthma. The registry lists enrollment of 37 and a completed status. The recorded start was 2007-11, and primary completion was 2008-04.

A crossover design means that participants receive more than one treatment over separate treatment periods, so comparisons can use measurements from the same participants under different conditions. The registry lists three treatment sequences involving indacaterol/mometasone, fluticasone/salmeterol, and placebo. The arm descriptions identify matching placebos for the two inhaler regimens, consistent with the double-dummy design. The full sequence schedule, including any washout details, is not reported in the registry record.

The primary outcome was change from each period’s baseline to 24-hour post-dose trough FEV1. The specified assessment schedule refers to baseline before each treatment period on Days 1, 8 and 15, and 24-hour post-dose measurements on Days 2, 9 and 16. The registry describes the primary analysis as using measurements after 1 day of treatment. It does not report the full treatment-period conduct or explain how all scheduled measurements related to the single-dose description in the title.

The primary analysis population was the Intent-To-Treat population, defined in the record by availability of baseline and post-baseline FEV1 measurements within at least one treatment period. The outcome counts show 36 participants for indacaterol/mometasone, 36 for fluticasone/salmeterol, and 35 for placebo. Those outcome counts need not match the total enrollment in a crossover study, where availability can vary by treatment period. The full participant flow and reasons for missing measurements 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 Period 1

Reasons for not completing this period:

Treatment Period 2

Treatment Period 3

Analysis population for the primary outcome, as defined in the registry: The Intent-To-Treat (ITT) population included all randomized patients who had at least one period containing a Baseline FEV1 measurement and at least one post-baseline measurement of FEV1 for the same treatment period. Patients who took rescue medication within 6 hours prior to the trough measurements were excluded from the analysis.

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 Change From Period Baseline to 24 Hour Post-dose (Trough) Forced Expiratory Volume in 1 Second (FEV1), measured over Pre-dose for each Treatment Period (Days 1, 8 and 15) and 24-hours post-dose for each Treatment Period (Days 2, 9 and 16)..

The primary endpoint was change from period baseline to 24-hour post-dose trough FEV1, measured in liters. FEV1 is the amount of air a person can forcibly exhale during the first second of a forced exhalation. A trough measurement taken 24 hours after dosing is intended to characterize lung function at that specified point in the dosing interval, rather than the peak response. The registry describes the primary analysis as assessing change after 1 day of treatment.

Change from baseline is used to express how an outcome differs from a participant’s starting measurement for that treatment period. In a crossover study, each participant may contribute measurements under more than one treatment, making the period-specific baseline relevant to interpreting changes. The registry’s analysis adjusted for treatment, period, sequence and center, used period baseline as a covariate, and included patient nested within sequence as a random effect.

The endpoint is a physiological measure, not a direct measure of symptoms or everyday functioning. Its interpretation is therefore specific: it describes the posted change in FEV1 at the defined trough assessment. The record also lists secondary measures involving FEV1 at single time points, standardized area under the curve between baseline and 24 hours, time to peak FEV1, and FVC at single time points. Those measures address different aspects of lung function and timing; four secondary outcomes are posted.

7. Results Posted in the Registry

• Indacaterol/Mometasone: mean 0.08 versus -0.08 on control; difference 0.16 (95% CI 0.03 to 0.30), standardized effect d = 0.58; z-test p = 0.014.
• Fluticasone/Salmeterol: mean 0.05 versus -0.08 on control; difference 0.13 (95% CI 0.00 to 0.26), standardized effect d = 0.47; z-test p = 0.049.

8. Statistical Interpretation

9. Statistical Methods Explained

The registry describes an analysis of covariance, or ANCOVA, for the primary outcome. ANCOVA models an outcome while adjusting for specified factors and a baseline measurement. Here, the listed adjustment factors were treatment, period, sequence and center, with period baseline as a covariate and patient nested within sequence as a random effect. These terms are relevant to a crossover design: treatment periods and the order of treatments can affect measurements, while repeated participation means observations from the same person are not independent.

Why adjust for treatment period and sequence?

In a crossover study, the treatment received in a period is considered alongside the period in which it was received and the sequence to which the participant was assigned. Period adjustment allows the model to account for systematic differences between periods. Sequence adjustment accounts for the assigned order of treatments. A patient-level random effect nested within sequence represents the correlation among measurements from a participant assigned to that sequence. These are general explanations of the model terms; details such as carryover testing or washout assumptions are not reported in the registry record.

What is a least-squares mean difference?

A least-squares mean is a model-based mean adjusted for the factors in the analysis. The sponsor reports an adjusted least-squares mean difference for indacaterol/mometasone versus placebo. It is not simply the difference between the two posted arm means, because the model accounts for its listed covariates and structure. The sponsor estimate is 0.165 liters. By contrast, the simple recalculation compares posted summary statistics without reproducing the ANCOVA and gives 0.164 liters. Because the registry flags a discrepancy, the sponsor’s own analysis takes precedence.

What does the standard error describe?

The arm summaries identify standard error as the dispersion measure. A standard error describes the estimated uncertainty in a mean, rather than the spread of individual participant measurements. It tends to be smaller when a mean is estimated more precisely, although its interpretation depends on the analysis and data structure. The record does not provide individual participant data, so the standard errors cannot reveal the distribution or variability of individual responses. The simple recalculation uses approximate standard deviations inferred from the posted standard errors; it is not a re-analysis of participant-level data.

How should the confidence interval be read?

A confidence interval gives a range of effect estimates compatible with the data and the analysis at the stated confidence level. In general, a wider interval indicates less precision than a narrower interval. The sponsor’s reported 95% interval for the placebo comparison runs from 0.066 to 0.263 liters. Its lower and upper limits are both above zero, while the estimate remains subject to sampling uncertainty. A confidence interval does not guarantee that the true effect lies in the interval, nor does it indicate whether the estimated difference is clinically important.

How should the p-value be read?

In general, a p-value measures how surprising data at least as extreme as those observed would be under a specified null hypothesis and model. The sponsor reports p = 0.001 for the adjusted indacaterol/mometasone versus placebo comparison. That value should be interpreted with the sponsor’s stated ANCOVA, not as a measure of effect size or certainty that a treatment effect exists. The unadjusted recalculation reports p = 0.014 for the same pair, reflecting a different calculation. The registry does not report the full inferential plan, including whether p-values were adjusted for multiple comparisons.

Why can simple recalculations differ?

The recalculations use the posted group summaries and make an unadjusted comparison. They do not incorporate the full crossover structure, the ANCOVA covariates, or the patient-level repeated-measure information in the sponsor model. The record identifies an approximate standard deviation for recalculation purposes, another reason that the result should not be treated as identical to the sponsor analysis. A small difference in an estimate can coexist with a difference in uncertainty and p-value because those quantities depend on the model and variance calculation as well as the group means.

What can the secondary analyses add?

The registry lists four posted secondary outcomes: FEV1 at single time points, standardized area under the curve between baseline and 24 hours, time to peak FEV1, and FVC at single time points. In general, single-time-point measures describe specific assessment times; area under the curve summarizes measurements across an interval; time to peak concerns response timing; and FVC measures a different forced-expiration volume. The registry record does not report enough secondary numerical results in this record to support detailed interpretation of their estimates. Their presence also matters for multiplicity: testing several outcomes or comparisons can increase the chance of at least one small p-value if no adjustment is used.

The model description is informative but incomplete. The registry record does not report the full statistical analysis plan, the original sample-size justification, interim analyses, detailed assumptions about missing observations, or a multiplicity procedure. These omissions limit independent reproduction and prevent a complete assessment of how the reported analysis was selected and interpreted.

10. Confidence Intervals and Precision

The sponsor’s adjusted estimate for indacaterol/mometasone versus placebo is 0.165 liters, with a 95% confidence interval from 0.066 to 0.263. The interval expresses uncertainty around the estimated adjusted difference. Its endpoints are both above zero, and the interval also spans a range of possible magnitudes; it does not identify one exact effect. The sponsor reports p = 0.001 for this analysis.

Precision depends on the amount and structure of the data, the variability of the endpoint, and the analysis model. This was a crossover study with outcome counts of 36 for indacaterol/mometasone and 35 for placebo. Those counts are modest, and the interval communicates uncertainty in the estimated contrast. The sponsor’s interval is based on the adjusted ANCOVA, not the unadjusted summary-statistic recalculation.

The recalculated mean difference is 0.164 liters, but its uncertainty calculation differs from the sponsor’s. Because the registry flags a discrepancy, the sponsor’s own analysis takes precedence. The recalculation should be used only as a simple descriptive check, not as an alternative confidence interval for the reported ANCOVA.

A confidence interval is not a range of individual participant outcomes, and it does not describe how much participants’ measurements varied. It also does not determine whether an effect is clinically meaningful. The registry record does not state a threshold for clinical importance. The interval therefore supports a statistical reading of the estimated treatment contrast, while clinical interpretation requires context not reported in the registry record.

11. 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 participants per arm, not total events. They are illustrations based on the observed effect, not the original trial’s design calculation. The assumptions listed for these illustrations are a two-sided significance level of 0.05, equal allocation between the two arms, a normal approximation, and an effect to detect set at the stated fraction of the observed effect. The original design assumptions and sample-size justification are not reported in the registry record.

The 80% power column gives the planned participants per arm under which the calculation would have an 80% chance of detecting the chosen effect at the stated significance level, assuming the planning model is correct. The 90% power column uses a higher target chance of detection under those same assumptions. For indacaterol/mometasone versus placebo, planning for 100% of the observed effect gives 47 participants per arm for 80% power and 63 participants per arm for 90% power. Planning for 75% gives 83 and 111 participants per arm, respectively; planning for 50% gives 187 and 250.

For fluticasone/salmeterol versus placebo, the corresponding figures are 72 and 96 participants per arm for 100% of the observed effect, 128 and 171 for 75%, and 287 and 384 for 50%. Smaller effects require more participants to detect under these assumptions, which is why the planning counts rise as the target fraction falls. These are planning illustrations, not observed power; they do not describe the probability that the completed trial detected its true effect.

The illustrations use two-arm equal allocation and a normal approximation, whereas the trial itself was a crossover study with three treatment conditions. They should not be read as a reconstruction of the trial’s actual design or as a direct recommendation for a future crossover study. Original design assumptions are not reported in the registry record.

12. 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 = 0.164; pooled standard deviation σ = 0.282.
2. n = 2 × (1.96 + 0.842)² × 0.282² / 0.164² = 46.6, rounded up to 47 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 <- 0.164                      # observed difference in means
sigma <- 0.282430519864133                     # 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(557440)
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 = 47 (80% power), 63 (90% power)
 75% of observed effect: n per arm = 83 (80% power), 111 (90% power)
 50% of observed effect: n per arm = 187 (80% power), 250 (90% power)
power.t.test: 47.5 
Simulated power at n = 47 per arm: 0.797 (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.

13. Analyses Reported by the Sponsor

The sponsor’s reported primary comparison is indacaterol/mometasone versus placebo using ANCOVA. It gives an adjusted least-squares mean difference of 0.165 liters, a 95% confidence interval from 0.066 to 0.263, and p = 0.001. This is the registry’s reported analysis for that comparison.

The simple recalculation from the posted summary statistics gives a mean difference of 0.164 liters and p = 0.014. It is unadjusted and does not reproduce the sponsor’s crossover ANCOVA. The record flags a discrepancy between the recalculation and the reported analysis; accordingly, the sponsor’s own analysis takes precedence. The close point estimates do not make their inferential results interchangeable.

The recalculation is useful as a transparent check on the direction and approximate size of the contrast using group summaries. It cannot verify the adjusted model or replace the analysis based on the trial’s treatment, period, sequence, center, baseline and patient-level structure. A sponsor ANCOVA for the active-control comparison is not reported in the registry record, so the unadjusted recalculation for fluticasone/salmeterol versus placebo should not be described as a sponsor result.

14. Multiplicity, Missing Data and Analysis Populations

The registry lists a primary outcome and four secondary outcomes, and the study includes comparisons involving placebo and an active control. When multiple outcomes or treatment comparisons are tested, the chance of obtaining at least one small p-value can increase. As a general statistical matter, a multiplicity procedure can control or otherwise address this issue, but the procedure used in this trial is not reported in the registry record. The reported p-values should therefore be interpreted as belonging to their respective analyses, without assuming a correction or a prespecified testing hierarchy.

The primary outcome population is described as the Intent-To-Treat population, including randomized patients with at least one treatment period containing baseline and post-baseline FEV1 measurements for that same period. The registry description adds a condition concerning rescue medication within 6 hours before the trough measurement, but the text is truncated. The complete population definition and the handling of measurements affected by rescue medication are not reported in the registry record.

The outcome counts differ by treatment: 36 for indacaterol/mometasone, 36 for fluticasone/salmeterol, and 35 for placebo. This does not establish why measurements were unavailable or whether every randomized participant contributed to every analysis. Full participant flow, reasons for missing measurements, and the statistical method for handling missing data are not reported in the registry record. In a crossover study, incomplete observations in one period can affect which within-participant comparisons are available, so these details matter for understanding the analysis population.

The registry gives an ANCOVA model description but does not report the full statistical analysis plan, interim analyses, or the original sample-size rationale. It also does not report whether the primary analysis was modified after data collection or how model assumptions were checked. Those omissions limit the ability to assess the complete analysis strategy or independently reproduce the sponsor’s result from the registry record alone.

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 non-serious adverse event terms

The serious adverse event figures list 0 affected participants among 36 at risk for indacaterol/mometasone, 0 among 36 for fluticasone/salmeterol, and 0 among 37 for placebo. These are counts of participants with serious adverse events, not a measure of all symptoms or adverse events. The registry lists no serious adverse event terms.

The record also lists other, non-serious adverse events affecting 2 participants in the indacaterol/mometasone group, 1 in the fluticasone/salmeterol group, and 2 in the placebo group. These figures are separate from the serious-event counts and should not be combined with them. Death counts are not reported in the registry record.

Zero reported serious adverse events in these groups describes what is recorded for this trial; it does not establish that serious events are impossible or rule out uncommon risks. Enrollment was 37, and the number at risk varied by treatment in the safety figures. The registry record does not provide enough detail to characterize event timing, duration, severity beyond the serious/non-serious classification, or causal attribution.

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

The posted primary result is an adjusted comparison of change in 24-hour trough FEV1 between indacaterol/mometasone and placebo. The sponsor reports a least-squares mean difference of 0.165 liters, with a 95% confidence interval from 0.066 to 0.263 and p = 0.001. The result describes the estimated contrast under the sponsor’s ANCOVA model in this randomized crossover study.

It does not establish that the same contrast would occur in every population or setting. The study was Phase 2 and enrolled 37 participants. It measured a specific physiological endpoint at a defined short-term assessment. The registry record does not report a clinical-importance threshold, so statistical evidence should not be equated with a judgment about the importance of the measured difference to patients.

The result also does not establish effects on symptoms, longer-term asthma control, exacerbations, or other outcomes not reported in the primary result. Although secondary outcomes are listed, the available record does not provide enough numerical detail to interpret all of them. A direct sponsor comparison of indacaterol/mometasone with fluticasone/salmeterol is not reported in the registry record; the recalculated active-control contrast is not a substitute for such an adjusted analysis.

Finally, the simple recalculation and sponsor result are not interchangeable. The recalculated mean difference is 0.164 liters with p = 0.014, whereas the sponsor’s adjusted result is 0.165 liters with p = 0.001. The discrepancy means that the sponsor analysis takes precedence for the reported primary comparison. The recalculation is a limited check based on summary statistics and cannot reproduce the trial’s full model.

17. Why This Trial Matters Statistically

This trial is statistically instructive because it combines a randomized crossover design with an adjusted repeated-measures analysis. Treatment, period and sequence are explicit model terms, and patient nested within sequence is included as a random effect. These features illustrate why a straightforward difference between treatment-group means may not reproduce the trial’s primary analysis.

The registry also makes the distinction between a sponsor analysis and a simple recalculation consequential. The posted sponsor estimate and recalculated estimate are close, yet the reported confidence interval and p-value differ from those generated by the unadjusted summary-statistic approach. Treating the recalculation as if it were the sponsor’s result would obscure the role of the crossover model and its adjustment structure.

Another useful statistical lesson is that a small trial can produce an estimate that is interpretable but still uncertain. The sponsor’s confidence interval gives a range for the adjusted contrast, while the enrollment and outcome counts convey the scale of the evidence base. The result must be read as an estimate from this study, not as a precise universal value.

Finally, the sample-size illustrations show how planning depends on the effect one aims to detect: smaller target effects require more participants under the listed assumptions. Because those illustrations are not the trial’s original design calculation and use a two-arm framework, they should not be mistaken for a description of how this crossover study was planned.

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 study enrolled 37 participants, and the primary outcome counts were 36 for indacaterol/mometasone, 36 for fluticasone/salmeterol, and 35 for placebo. The record does not explain the differences in available outcome counts or give the full participant flow. This makes it difficult to assess how missing observations affected the treatment-period comparisons.

The registry’s primary population description is truncated, including its statement about rescue medication before the trough measurement. The complete eligibility and analysis-population rules are therefore not reported in the registry record. The record also does not report the full statistical analysis plan, the original sample-size justification, interim analyses, the multiplicity approach, or the method used to handle missing data.

The sponsor’s adjusted placebo comparison is reported, but an adjusted sponsor comparison with fluticasone/salmeterol is not reported in the registry record. The simple recalculations are unadjusted and do not reproduce the crossover ANCOVA. The discrepancy flag reinforces that they should not replace the sponsor analysis.

The result concerns a short-term physiological endpoint, with the primary outcome described as change to 24-hour post-dose trough FEV1 after 1 day of treatment. The registry record does not state a threshold for clinical importance and does not provide enough detail to assess longer-term outcomes. The crossover sequence and double-dummy features are described, but complete period and washout details are not reported in the registry record.

19. Related Tutorials

20. Related Statistical Calculators

21. Sources

• ClinicalTrials.gov: Investigation of the 24 Hour Forced Expiratory Flow in 1 Second (FEV1) Profile of a Single Dose of Indacaterol/Mometasone Delivered Via the TWISTHALER® Device in Adult Patients With Persistent Asthma — NCT00557440.
• Registry record last updated 2013-03-21; status last verified 2009-04.
• Results first posted 2013-03-21.
• 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

NCT00557440 is a completed Phase 2 randomized, quadruple-masked, double-blind, double-dummy crossover study sponsored by Novartis. It enrolled 37 adults with persistent asthma and compared indacaterol/mometasone with placebo, with fluticasone/salmeterol as an active control.

The primary endpoint was change from period baseline to 24-hour post-dose trough FEV1. The sponsor’s ANCOVA comparison of indacaterol/mometasone with placebo reported an adjusted difference of 0.165 liters, a 95% confidence interval from 0.066 to 0.263, and p = 0.001. A simple recalculation differs and does not replace the sponsor analysis. The registry lists four secondary outcomes and reports 0 serious adverse events in each treatment group.