SERETIDE Vs FLIXOTIDE In Mild Persistent Asthma (GINAII): Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for SERETIDE Vs FLIXOTIDE In Mild Persistent Asthma (GINAII) (NCT00455923), a randomized phase 4 study. The primary outcome is Number of Participants in Each Arm With a Need for an Increase in Study Medication.

2. Clinical Question

3. Trial Design

This was a Phase 4 randomized trial with a parallel-arm design. The registry describes it as double-blind and reports an enrollment of 100. The two study arms were Seretide and Flixotide. The record lists GlaxoSmithKline as sponsor and gives the trial status as completed. The recorded start date is 2005-05-03, and the primary completion date is 2007-07-31.

The brief summary describes an 18 months study. It says the first 6 months were a dose-adjustment phase, during which treatment could be increased until asthma was well controlled. It then describes treatment continuing without changes during a 9 months Phase II. The primary outcome is specified as occurring up to 18 months, and the primary endpoint description says treatment was fixed after the initial 6 months. The registry record does not explain how the named phase durations map onto the full stated follow-up duration.

Both arms began with inhaled treatment twice daily using a Diskus inhaler. Seretide combined Sal/FP, while Flixotide contained FP only. Dose increases during the initial period were conditional on asthma remaining unstable or uncontrolled. Because dose escalation was part of the intervention approach, the outcome measures whether an increase was needed rather than simply comparing fixed-dose regimens.

The primary population is described as Intent-to-Treat: participants randomized and given at least one dose of study medication. The arm counts in the primary result are 50.0 for Seretide and 50.0 for Flixotide. The registry record does not report further details about concealment of allocation, the blinding procedure, adherence, or the criteria used to determine that an increase was needed.

4. Participant Flow and Accounting

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

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: Intent-to-Treat (ITT) Population which comprised of all participants who were randomized and received at least one dose of the study medication.

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 Number of Participants in Each Arm With a Need for an Increase in Study Medication, measured over Up to 18 months.

The primary endpoint is the number of participants in each arm with a need for an increase in study medication, measured up to 18 months. It is a count of participants who experienced the event, not a measure of the number of dose increases per participant. The endpoint description indicates that dose escalation could occur during the first 6 months, while treatment was fixed after that initial period.

This outcome is relevant to the study question because the trial aimed to compare the control of mild persistent asthma under combination therapy with Seretide against inhaled corticosteroid treatment with Flixotide alone. A need to increase medication is one way to represent that the starting or current dose was not considered sufficient under the trial's rules. It does not, by itself, capture every aspect of asthma control, symptom burden, lung function, or quality of life.

The registry lists secondary outcomes concerning bronchial hyper-responsiveness, symptom-free days and nights without rescue medication, exacerbations, and time to increase study medication. These offer other perspectives on response and disease course. The operational criteria for deciding that an increase was required, including how that decision was applied across sites or assessors, are not reported in the registry record. The posted primary result therefore gives the event counts and comparison, but does not give enough detail to independently assess the decision process behind each event.

7. Results Posted in the Registry

• Flixotide: 58.0% (29/50) versus 58.0% (29/50) on control; risk difference 0.0 percentage points (95% CI -19.3 to 19.3), risk ratio 1.00 (0.72–1.40); unadjusted two-proportion z-test p = 1.000.

8. Statistical Interpretation

9. Statistical Methods Explained

The primary endpoint is binary at the participant level: each participant either had a recorded need for an increase in study medication or did not. The posted arm summaries give the number with the event and the number reported in each arm. For this type of outcome, a comparison can be expressed on an absolute scale, such as a risk difference, or on a relative scale, such as a risk ratio or odds ratio. These measures answer related but different questions.

What does the risk difference express?

General statistical explanation: a risk difference subtracts the event proportion in one group from the event proportion in the other group. A value of 0.0 represents equal observed proportions. The registry reports a risk difference of 0.0 for this comparison, with an interval from -0.194 to 0.194. The negative and positive limits represent possible directions of difference under the interval procedure used. The interval method itself is not reported in the registry record, so its construction cannot be independently evaluated from the posted information.

An absolute difference is often straightforward to interpret because it is expressed in proportion units. It describes the size of the contrast between the observed groups, not the probability that an individual participant will experience the event. The corresponding confidence interval shows the range of values compatible with the data under the method's assumptions. Since the interval spans 0.0, it includes no difference as well as differences in either direction.

How do relative measures differ?

General statistical explanation: a risk ratio compares event proportions by division, while an odds ratio compares the odds of the event. A value of 1.0 is the null value for each measure. The record reports a risk ratio of 1.0 with limits 0.716 and 1.396, and an odds ratio of 1.0 with limits 0.452 and 2.213. The point estimates express equality in the posted data, but the intervals include values below and above 1.0. Relative and absolute measures can convey different impressions of magnitude, so interpretation should keep the measure's scale explicit.

For common outcomes, an odds ratio can be farther from 1.0 than the corresponding risk ratio for the same underlying comparison. General statistical explanation: this distinction arises because odds and probabilities are different quantities, especially when an event is not rare. The registry reports both measures, but does not report a rationale for selecting them or identify one as the primary effect measure. The endpoint itself is a participant count; the risk difference is a natural absolute-scale summary for such data.

What does the p-value tell us?

The unadjusted p-value is 1.0. General statistical explanation: a p-value summarizes how inconsistent the observed data are with a specified null hypothesis, assuming the statistical model and its assumptions apply. It is not the probability that the null hypothesis is true, and it does not quantify the probability that chance alone caused the result. A large p-value does not establish equivalence or prove that any possible difference is absent.

The record does not identify the test used to obtain this p-value. It is labeled unadjusted, so no multiplicity adjustment is reflected in that reported value. The record does not describe whether covariates were considered, whether the analysis followed a prespecified plan, or whether the comparison was chosen after examining data. Those details are not reported in the registry record.

What assumptions matter for this endpoint?

General statistical explanation: a simple comparison of two participant-level binary outcomes generally treats each participant's outcome as one observation and assumes that the observations are independent across participants. Randomization supports a causal comparison when allocation and follow-up are handled appropriately, but it does not correct missing outcome data, deviations from assigned treatment, or errors in outcome classification. The registry record describes randomization but does not report the analysis procedure in enough detail to assess these issues.

Over-dispersion is more commonly a concern for count models when observed variability exceeds the model's assumed variability. It is not automatically a feature of a binary participant-level endpoint, where each person contributes an event or non-event. General explanation: if repeated events per participant were being modeled, within-person clustering and extra variability could matter; this primary outcome instead reports the number of participants with a need for an increase. The registry does not report a repeated-event model for this endpoint.

The sample-size assumptions described for planning are illustrations based on the observed effect, with a two-sided significance level of 0.05, equal allocation, and a normal approximation; the effect to detect is a stated fraction of the observed effect. These planning assumptions are not evidence of observed power, and they are not the trial's original design justification. The registry record does not report the original sample-size rationale or identify a prespecified target effect. No planning participant counts are stated in the registry information considered for this explanation.

10. Confidence Intervals and Precision

The central estimate for the primary comparison is a risk difference of 0.0. Its confidence interval runs from -0.194 to 0.194. This interval is the main guide to the precision of the absolute comparison: it includes the null value of 0.0 and also allows for differences on either side. The posted result therefore has a point estimate of no observed difference, but the interval does not restrict the plausible contrast to equality.

General statistical explanation: a confidence interval is produced by a method that, under its assumptions and in repeated use, has a stated coverage property. It is not a range containing a fixed proportion of individual participant outcomes, and it is not the probability that the true effect lies within these particular limits. The method used for this interval is not reported in the registry record. Its limits should consequently be interpreted as the reported uncertainty interval, without assuming a specific calculation procedure.

The relative summaries also show uncertainty. The risk ratio is 1.0, with interval limits 0.716 and 1.396. The odds ratio is 1.0, with interval limits 0.452 and 2.213. Both intervals include 1.0, their null value. Their scales differ from the risk-difference scale, and their widths should not be compared as if they used the same units.

The same event count in each arm does not remove sampling uncertainty. General explanation: trial results describe the participants observed, while an estimate intended to represent a broader population remains uncertain because a different randomized sample could produce different counts. Precision depends on the amount of information and on the statistical method, not solely on whether the observed counts match.

The interval is wide enough to retain uncertainty about the magnitude and direction of a possible difference. The registry record does not report a prespecified equivalence margin or non-inferiority margin. Thus, the result cannot be interpreted as demonstrating equivalence or non-inferiority. It supports a narrow descriptive statement about the posted data: the observed proportions were equal, while the reported interval remains compatible with a range of underlying contrasts.

11. Multiplicity, Missing Data and Analysis Populations

The registry lists five secondary outcomes covering bronchial hyper-responsiveness, symptom-free days and nights without rescue medication, exacerbations, and time to increase study medication. It reports six outcome measures in total. The registry record does not report results for the listed secondary outcomes, so their estimates and uncertainty cannot be assessed alongside the primary outcome.

Multiplicity arises when several outcomes or comparisons are examined. General statistical explanation: as the number of statistical tests increases, the chance of at least one apparently unusual result can increase if each test is assessed separately. Approaches such as prespecifying a primary outcome or adjusting for multiple tests can address different multiplicity concerns, but the approach depends on the questions and analysis plan. The registry record does not report a multiplicity strategy, a hierarchy among secondary outcomes, or an adjustment to the primary comparison. The posted p-value is labeled unadjusted.

The primary population is described as Intent-to-Treat, including participants who were randomized and received at least one dose of study medication. The registry does not state how many participants had missing primary outcomes, whether all eligible participants contributed to the posted comparison, or how missing data were handled. It also does not report sensitivity analyses for missingness or departures from the assigned treatment.

The record lists no analyses in its analysis summary. That does not provide enough detail to determine whether analyses were performed but not entered in the registry, or whether the posted comparison was the only analysis. The statistical analysis plan and the rationale for the analytic choices are not reported in the registry record. Accordingly, the posted primary result can be described, but the role of prespecification, multiplicity control, and missing-data procedures cannot be verified from the registry entry.

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: colon diverticulitis (2.0%), migraine/headache (2.0%), cholecystitis (2.0%).

The registry reports serious adverse events affecting 3 participants in the Seretide arm and 0 in the Flixotide arm. The at-risk count is 50 for each arm. It reports 0 deaths in both arms. These are descriptive counts from the safety information in the registry record; they do not by themselves establish whether an event was caused by study treatment.

The record lists Colon diverticulitis, Migraine/headache, and Cholecystitis among the top serious terms, each reported as 2.0%. These terms should be read as the registry's listed serious-event categories, not as a complete narrative of every event or its clinical course. The registry record does not provide further detail in the information about timing, severity beyond the serious classification, management, or causal assessment for these terms.

The record also reports other adverse events affecting 48 participants in the Seretide arm and 47 in the Flixotide arm, with 50 at risk in each arm. Serious adverse events and other adverse events are separate reported categories and should not be added together. These figures are counts, not comparative estimates adjusted for exposure time or other factors. The registry record does not report an inferential safety comparison, exposure-adjusted rates, or a detailed account of how events were collected.

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

The result establishes what was observed in the posted primary comparison: 29.0 participants in each arm were reported as needing an increase in study medication, and the registry reports 50.0 participants in each arm for the comparison. The estimated risk difference is 0.0, with an interval from -0.194 to 0.194. The unadjusted p-value is 1.0. This is a description of the analyzed trial outcome, not a general conclusion about asthma treatment.

The result does not show that the true effects are identical. The confidence interval includes possible differences in either direction, and no equivalence or non-inferiority margin is reported. A failure to find a difference in this comparison is not proof that there is no difference. Likewise, the p-value is not a measure of clinical importance and does not tell readers whether the study was large enough to resolve a difference that might matter.

The endpoint is specifically a need for medication increase under a protocol that allowed stepwise dose escalation during the first 6 months and fixed treatment afterward. It is not a complete measure of symptom control or every clinical outcome. Secondary outcomes are listed, but their results are not reported in the registry record. The primary finding therefore should not be generalized to outcomes that were not posted.

The scope is also limited to the trial population and study conditions. The registry identifies mild persistent asthma and describes participants eligible for the study, but it does not give the characteristics needed to judge how closely that group resembles other populations. The result does not establish what would occur under different dosing approaches, follow-up periods, or clinical settings.

Finally, the registry record does not report key analytic details, including the interval method, missing-data handling, or the prespecified statistical plan. These gaps do not change the posted estimates, but they constrain how fully readers can evaluate their robustness. The careful conclusion is that the registry reports equal observed event proportions for this outcome, with uncertainty that remains compatible with a range of differences.

14. Why This Trial Matters Statistically

This trial is statistically informative because it illustrates the difference between an observed point estimate and the precision of that estimate. The two arms have the same posted count of participants needing an increase in medication, and the risk-difference estimate is 0.0. A reader looking only at the point estimate might conclude that the groups were identical. The confidence interval shows why that conclusion would go beyond the data: a range of differences remains compatible with the result.

It also makes the choice of effect scale visible. A risk difference describes an absolute contrast, while risk ratios and odds ratios describe relative contrasts. The registry reports all three, with point estimates at their respective null values. Their intervals contain uncertainty that cannot be conveyed by the matching event counts alone. Statistical interpretation is stronger when the estimate, interval, and outcome definition are considered together.

The endpoint connects the analysis to a practical treatment decision within the trial: whether study medication needed to be increased. Its interpretation depends on the dose-adjustment rules and follow-up period. Because treatment could be escalated during the first 6 months and was then fixed, this outcome reflects the study's management strategy as well as the underlying asthma response.

The record also highlights the importance of transparent reporting. The primary population is defined, but the analysis method, missing-data approach, multiplicity strategy, and original sample-size rationale are not reported. Readers can interpret the posted comparison, yet cannot fully verify how analytic decisions were made or how much weight to place on unreported secondary outcomes. This distinction between available results and unreported methods is important when judging the reach of a registry finding.

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.

The registry record does not report baseline characteristics, so the balance and clinical profile of the analyzed population cannot be assessed from the primary result. The primary population is defined as randomized participants who received at least one dose, but the record does not state whether all such participants had outcome data or how missing observations were handled. This limits evaluation of potential bias from incomplete follow-up.

The endpoint is described as a need for increase in study medication, but the decision criteria and ascertainment procedures are not reported. Without those details, it is difficult to judge consistency in event classification. The outcome is also tied to the trial's dose-escalation approach, including stepwise increases during the initial 6 months and fixed treatment afterward; its interpretation may not transfer directly to settings using different treatment rules.

The registry describes an 18 months study and identifies a 6-month initial phase and a 9-month Phase II in the brief summary. The record does not explain how the phase durations align with the stated full follow-up. The primary outcome timeframe is listed as up to 18 months, but detailed follow-up and censoring information is not reported.

Only the primary comparison is presented with an estimate and interval in the posted results. Although secondary outcomes are listed, their results are not reported in the registry record. The statistical analysis plan, interval method, multiplicity approach, and sample-size justification are also not reported. These limitations constrain interpretation of both the statistical robustness and the broader clinical picture. The available result should therefore be treated as a specific registry-reported comparison rather than a complete account of all trial findings.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: SERETIDE Vs FLIXOTIDE In Mild Persistent Asthma (GINAII) — NCT00455923.
• Registry record last updated 2018-02-05; status last verified 2018-01.
• Results first posted 2018-01-04.
• 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 NCT00455923, a completed Phase 4 randomized, double-blind, parallel-arm study sponsored by GlaxoSmithKline. It enrolled 100 participants with asthma and compared Seretide with Flixotide. The study is described as lasting 18 months, with dose adjustment during the first 6 months and treatment fixed afterward.

The primary outcome was the number of participants needing an increase in study medication up to 18 months. In the Intent-to-Treat population, the record reports 29.0 participants with the event in each arm, with 50.0 participants in each arm. The risk difference is 0.0, with a confidence interval from -0.194 to 0.194 and an unadjusted p-value of 1.0.

Secondary outcomes are listed, but their results are not reported in the registry record. The record also does not report the statistical analysis plan or missing-data procedures.