Omalizumab in Adult and Adolescent Patients With Severe Persistent Allergic Asthma: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Omalizumab in Adult and Adolescent Patients With Severe Persistent Allergic Asthma (NCT00264849), a randomized phase 4 study. The primary outcome is Persistency of Response and Non-response as Based on Investigator's Global Evaluation of Treatment Effectiveness (GETE).

2. Clinical Question

The comparison is about the persistence of a categorized global assessment, not simply whether participants had a response at a single visit. Investigators classified treatment effectiveness as excellent, good, moderate, poor, or worsening. Excellent and good were grouped as response; moderate, poor, and worsening were grouped as non-response. The primary outcome then distinguished participants whose Week 16 category persisted from those whose category did not persist.

The trial also listed secondary outcomes relating to patient and investigator global assessments, lung function, asthma control, exacerbations, and medical resource use. These outcomes address different aspects of asthma status and treatment experience. Their presence in the registry record does not establish what was observed: results for them are not reported in the registry record.

3. Trial Design

This was a Phase 4, randomized, open-label, parallel-group study of omalizumab as add-on treatment to optimized asthma therapy. The registry describes an international, multicenter study in adults and adolescents with severe persistent allergic asthma who remained inadequately controlled despite GINA (2004) Step 4 therapy. Enrollment was 406. The study status is completed; the recorded start was 2005-11 and primary completion was 2008-09.

Both groups underwent an 8-week run-in during which asthma therapy was evaluated and optimized. During the subsequent 32-week treatment phase, one group continued optimized asthma therapy and also received omalizumab. The comparator group continued optimized asthma therapy alone. Thus, the contrast is add-on treatment versus the optimized background treatment, rather than omalizumab versus no asthma therapy. The registry does not describe a placebo intervention.

Random allocation can support a comparison between assigned groups by reducing systematic differences at the point of assignment, although it does not guarantee that every measured or unmeasured characteristic is balanced. The open-label design means masking was absent. Awareness of treatment assignment may affect assessments or participant reports, particularly for global judgments of treatment effectiveness. The registry record does not report additional procedures intended to address this possibility.

The primary outcome was assessed at Weeks 16 and 32 and concerned persistence of investigator-rated response or non-response. The efficacy population was defined as randomized participants who had at least one post-baseline efficacy assessment. A participant could be assessed for persistence if they were a responder at Week 16 and had a second GETE assessment at least 4 weeks later, or discontinued prematurely for unsatisfactory therapeutic effect at least 4 weeks after the Week 16 assessment. Further details about allocation procedures, stratification, and the rationale for the enrollment target 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.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: Modified Intent-to-Treat (mITT) was defined for efficacy analyses which included all randomized patients who had at least one post-baseline efficacy assessment.

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 Persistency of Response and Non-response as Based on Investigator's Global Evaluation of Treatment Effectiveness (GETE), measured over Weeks 16 and 32.

The primary endpoint measures whether an investigator's global evaluation of treatment effectiveness remained in the same broad response category over time. GETE categories were dichotomized: excellent or good counted as response, while moderate, poor, or worsening counted as non-response. Persistent response meant response at Week 16 and again at Week 32. Persistent non-response meant non-response at both assessments.

This endpoint is used to describe consistency over time, rather than a status at a single visit. A participant's Week 16 result alone cannot establish persistence; a later assessment is needed. The registry also specifies when a participant could be assessed: a Week 16 responder needed a second GETE at least 4 weeks later, or premature discontinuation for unsatisfactory therapeutic effect at least 4 weeks after Week 16. That eligibility condition is part of the endpoint definition and should be considered when interpreting any reported counts.

The endpoint is based on a categorized judgment by the investigator. It is therefore not a direct measurement of lung function or a count of exacerbations. It also does not, by itself, convey the degree of improvement within a category or changes that may occur between assessment times. The registry record does not report the observed endpoint counts or the comparison between treatment groups, so the extent of persistent response cannot be determined from the record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does the primary outcome classify?

The endpoint starts with GETE, the investigator's global evaluation of treatment effectiveness. The registry groups excellent and good evaluations as responders. Moderate, poor, and worsening evaluations are grouped as non-responders. It then considers status at both Week 16 and Week 32. Persistent response means response at both times; persistent non-response means non-response at both times.

General: dichotomizing an ordered scale makes a summary easier to interpret, but it discards distinctions within each group. For example, the endpoint does not distinguish excellent from good once both are classified as response. Nor does the persistent-response definition describe the size of any change in asthma status. A shift between categories can be hidden by grouping, while a transition across the response threshold changes the classification.

Why does the timing rule matter?

The registry says participants were assessed for persistence if they were responders at Week 16 and had a second GETE assessment at least 4 weeks after Week 16, or discontinued prematurely for unsatisfactory therapeutic effect at least 4 weeks after Week 16. This is not simply an outcome measured for every randomized participant regardless of follow-up. The qualifying rule ties assessment to a Week 16 response and the availability or timing of later information. The record does not fully describe how all other patterns of missing assessments were handled.

General: when outcome availability depends on earlier status or subsequent follow-up, the population with an evaluable outcome may differ from the full randomized population. Interpretation should therefore consider both the endpoint definition and the analysis population. The registry's mITT definition includes randomized participants with at least one post-baseline efficacy assessment; the primary outcome's additional persistence criteria are also relevant to understanding who could contribute.

What can randomization and open-label conduct tell us?

Randomization assigns participants to groups by chance. General: this can reduce systematic differences between groups at assignment and strengthens the basis for comparing outcomes, provided the analysis and follow-up preserve the intended comparison. The registry identifies the study as randomized but does not report the sequence-generation method, allocation concealment, or any stratification factors.

The trial was open label, with no masking. General: knowing the assigned treatment can influence participant-reported outcomes, clinician judgments, care decisions, or the likelihood that outcomes are assessed in a particular way. This concern is relevant to GETE because it is a global evaluation. It does not establish that an assessment was biased; it identifies a possible source of measurement and performance effects. The registry does not report whether outcome assessors were independently masked.

How should statistical significance and precision be read?

The registry record does not report primary outcome estimates, confidence intervals, or p-values. Consequently, there is no posted numerical treatment contrast from which to assess statistical significance or precision. General: a p-value measures how compatible observed data are with a specified null model, given the analysis assumptions; it is not the probability that the null hypothesis is true. A confidence interval gives a range of values compatible with the data and method at the stated confidence level. Neither can be interpreted when the corresponding estimate and analysis are absent.

The sample-size assumptions describe planning illustrations based on an observed effect, with a two-sided significance level of 0.05, equal allocation, and a normal approximation. They state that the effect to detect is a stated fraction of the observed effect. These are planning conventions, not evidence that the study had a particular probability of detecting its actual effect. Such illustrations are not observed power. No sample-size justification from the trial's own design is reported in the registry record.

General: an illustration based on a previously observed effect depends on that effect being a suitable planning input. If the effect is uncertain, the illustration is uncertain too. A sample-size calculation also depends on the chosen outcome, statistical model, significance threshold, allocation assumptions, and target power. The registry record does not supply a trial-specific rationale or enough primary outcome results to evaluate a calculation for this endpoint.

What about counts, dispersion, and event outcomes?

The primary outcome is described in terms of participants and categorized response status. Secondary outcomes include both continuous measures, such as FEV1 and ACQ score change, and event-related measures, such as exacerbations and resource use. The registry does not report their observed results or statistical models.

General: continuous outcomes are often summarized by a location measure and an estimate of uncertainty, while event counts may require methods that account for the distribution of event frequencies. Over-dispersion occurs when event variability exceeds what a simple count model assumes; accounting for it can prevent uncertainty from being understated. This is a general statistical consideration, not a description of the analysis used in this trial. The registry does not report whether over-dispersion was assessed or what models were used for these secondary outcomes.

The sample-size assumptions distinguish planning illustrations for time-to-event outcomes, which use total events, from other outcomes, which use participants per arm. The primary endpoint is a participant classification at specified assessment times, not a time-to-event endpoint as defined in the registry. No calculated planning values for this endpoint are reported in the registry record.

What is not available for independent checking?

The record does not report the primary outcome results, analysis methods, handling of missing outcomes, multiplicity procedure, interim analyses, or a trial-specific sample-size justification. Without these details, readers cannot reproduce the primary comparison, check the assumptions of an analysis, or judge how choices about incomplete follow-up and multiple outcomes were handled. General: transparency about those choices helps distinguish a prespecified analysis from analyses selected after results are known. Their absence from the registry record is a limit on what can be concluded from the posted information.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists 14 outcome measures, including the primary persistence outcome and secondary assessments of GETE, lung function, asthma control, exacerbations, and medical resource use. It does not report a multiplicity adjustment or a hierarchy for interpreting results across these outcomes. A plan for handling multiple comparisons is not reported in the registry record.

General: when many outcomes or repeated assessments are tested, the chance of at least one apparently unusual result can increase if each is considered separately. Prespecifying a primary outcome and a testing strategy can help make interpretation more disciplined. The record identifies a primary outcome but does not describe the statistical strategy for controlling or interpreting multiple testing.

The primary efficacy population is defined as randomized participants with at least one post-baseline efficacy assessment. The endpoint description also gives specific criteria for assessing persistence, including a later GETE assessment or premature discontinuation for unsatisfactory therapeutic effect at least 4 weeks after Week 16. The record does not explain how other missing assessments, incomplete follow-up, or participants not meeting the persistence assessment criteria were handled in the analysis.

Missing-data handling is not reported in the registry record. General: missing outcomes can affect a comparison if the likelihood of being observed is related to treatment or outcome status. Different assumptions or methods for incomplete data can produce different estimates, so the approach matters when interpreting a longitudinal endpoint. Interim analyses and any associated decision rules are also not reported. These omissions prevent assessment of whether multiplicity, incomplete observations, or interim monitoring influenced the reported analysis; in this case, primary outcome results themselves are not reported.

11. 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: asthma (10.9%), bronchitis (1.6%), road traffic accident (1.1%), melaena (0.8%), polyp (0.8%).

The registry reports serious adverse events affecting 29 of 274 participants assigned to OAT plus omalizumab and 17 of 128 assigned to optimized asthma treatment. It reports other adverse events affecting 140 of 274 participants in the OAT plus omalizumab group and 65 of 128 in the optimized asthma treatment group. These are participant counts as recorded, not a statistical comparison. No adjusted effect estimate or uncertainty interval is reported in the registry record.

The listed serious-event terms include Asthma (10.9%), Bronchitis (1.6%), Road traffic accident (1.1%), Melaena (0.8%), Polyp (0.8%), and Drug hypersensitivity (0.8%). The registry excerpt does not give event counts alongside these terms or further detail about their denominators, timing, severity, or relationship to treatment. These percentages should therefore be read as the listed registry values, not as independently calculated rates.

Serious adverse events and other adverse events are separate registry categories; the counts should not be combined. The record does not report death counts. A missing death count is not evidence of zero deaths. General: safety comparisons require attention to definitions, exposure time, event recurrence, severity, and uncertainty, as well as participant counts. The posted figures alone do not establish that a treatment caused an event or explain differences between groups.

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

The trial's design addresses an add-on treatment question: omalizumab alongside optimized asthma therapy compared with optimized asthma therapy alone. Its primary endpoint focuses on whether investigators classified participants as responders or non-responders at both Week 16 and Week 32. That is a persistence question, not a direct estimate of every aspect of asthma control or a measure of improvement in a continuous scale.

The registry record is not sufficient to determine the result of that comparison. It gives the endpoint definition and analysis-population definition, but does not report the observed primary outcome counts, a between-group estimate, or its uncertainty. It is therefore not possible to state from the registry record how often response persisted, whether the groups differed, or how precisely any difference was estimated.

The same caution applies to the listed secondary outcomes. Their presence indicates that the study included assessments of investigator and patient global evaluations, FEV1, ACQ score change, exacerbations, and resource use. It does not reveal their results. The safety record includes adverse-event counts and listed serious-event terms, but does not provide an adjusted comparison or full detail needed to establish causation.

General: a randomized comparison can inform an average contrast between assigned groups when results, follow-up, and analysis are available and appropriately interpreted. It does not automatically describe what will happen to every participant, and an open-label design can matter for outcomes based on judgment or report. Statistical uncertainty and the treatment of missing outcomes are also important to conclusions. Those features cannot be evaluated fully from this registry record.

The appropriate reading is therefore limited: the registry documents a completed randomized, open-label study and specifies a clinically framed persistence outcome, but does not provide the efficacy results needed to determine what the comparison showed. No conclusion that omalizumab did or did not improve persistent response follows from the endpoint description alone.

13. Why This Trial Matters Statistically

This trial is statistically notable for defining its primary question in terms of response persistence rather than a single follow-up assessment. A participant's status at Week 16 and Week 32 is used to distinguish persistent response from persistent non-response. This focuses attention on whether a broad investigator assessment remains consistent across time, rather than only on the status at one visit.

The endpoint also illustrates how a clinical scale can be simplified for analysis. GETE has several ordered categories, but the registry groups them into response and non-response. This can make a summary more straightforward, while losing distinctions among the categories within each group. For interpretation, it matters that the result would describe those grouped classifications, not the full distribution of investigator judgments.

The randomized comparison is between add-on omalizumab and optimized asthma therapy alone, after an optimization run-in. That design makes the comparator clinically specific: the question is not whether participants received asthma care, but whether adding omalizumab differs from continuing the optimized background therapy. The open-label nature of the study is particularly relevant because the primary endpoint depends on investigator judgment.

The registry's limited results reporting is itself important statistically. Without primary outcome counts, estimates, and uncertainty, readers cannot assess the observed contrast, its precision, or the robustness of the conclusion. The listed secondary outcomes and safety counts do not substitute for those missing efficacy results. This distinction between an endpoint being defined and its result being reported is essential when interpreting a trial record.

14. Limitations

• The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
• Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.

The most consequential limitation of the registry record is that it does not report the primary outcome results or a treatment-group comparison. The endpoint is described in detail, but no observed persistence counts, effect estimate, confidence interval, or p-value is available. The statistical and clinical magnitude of any difference therefore cannot be evaluated from the record.

The study was open label, and the primary outcome was an investigator's global evaluation. Awareness of treatment assignment could potentially influence ratings; the registry does not report masked assessment. This is a design consideration rather than proof that ratings were biased. The outcome's dichotomization also reduces detail by grouping excellent with good and moderate with poor or worsening.

The persistence assessment has eligibility criteria involving Week 16 response and follow-up or discontinuation timing. Although the mITT population is defined, the registry does not describe in detail how participants with incomplete or otherwise non-qualifying assessments were handled. Missing-data methods, the multiplicity strategy, interim analyses, and the trial-specific sample-size justification are not reported in the registry record.

The registry lists safety counts, but does not give the detail needed for a comprehensive comparative safety analysis, including event timing and exposure-adjusted comparisons. Death counts are not reported. The listed serious-event terms and percentages should not be treated as a complete account of event attribution or as evidence of causation.

Finally, the record identifies 14 outcomes but lists zero analyses. Without results and methods, readers cannot independently check model choices, uncertainty estimates, or consistency across outcome measures. The study's completed status does not resolve these reporting limitations.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Omalizumab in Adult and Adolescent Patients With Severe Persistent Allergic Asthma — NCT00264849.
• Registry record last updated 2018-06-29; status last verified 2018-04.
• Results first posted 2011-07-25.
• Data retrieved from ClinicalTrials.gov on 2026-11-09.
• Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.

18. Record Summary

NCT00264849 is a completed Phase 4 randomized, open-label, parallel-group study of omalizumab added to optimized asthma therapy versus optimized asthma therapy alone in adults and adolescents with severe persistent allergic asthma. The registry records enrollment of 406, a start in 2005-11, and primary completion in 2008-09.

Both groups had an 8-week run-in to evaluate and optimize asthma therapy, followed by a 32-week treatment phase. The primary outcome was persistence of investigator-rated GETE response or non-response at Weeks 16 and 32. The mITT efficacy population included randomized participants with at least one post-baseline efficacy assessment.

The registry does not report the primary outcome results or a treatment-group estimate. It lists secondary outcomes and adverse-event counts, but does not provide a statistical comparison for the primary endpoint. Missing-data handling, multiplicity procedures, interim analyses, and the trial-specific sample-size rationale are not reported in the registry record.