A Study of Xolair in Peanut-Allergic Subjects Previously Enrolled in Study Q2788g: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for A Study of Xolair in Peanut-Allergic Subjects Previously Enrolled in Study Q2788g (NCT00382148), a na phase 2 study. The primary outcome is Serious Adverse Events.

2. Clinical Question

The central question is descriptive safety, not a randomized estimate of treatment efficacy. The primary endpoint is the number of participants with a serious adverse event. The record also lists secondary outcomes concerning food allergen exposure on a patient-reported questionnaire, food-allergic reactions assessed by the Ewan Scale, nonserious food-related adverse events, and other nonserious adverse events.

The two groups reflect subjects’ prior status in Study Q2788g: one group is titled “Omalizumab (Placebo in Q2788g)” and the other “Omalizumab (Omalizumab in Q2788g).” This history can be useful when describing the participants and their reported events. It does not, by itself, support treating the groups as like-for-like controls in the current study. The registry explicitly identifies the current allocation as not applicable and warns that this is not a randomized comparison.

Accordingly, the most defensible reading is to ask what serious adverse events were recorded in each described group during the stated follow-up, while keeping the open-label, single-group design in view. The registry record does not report an inferential comparison or an analysis estimating a causal effect of omalizumab.

3. Trial Design

This was a Phase IIb, multicenter, open-label study of omalizumab in peanut-allergic subjects previously enrolled in Study Q2788g. It is listed as completed. The record gives a start date of 2006-11 and a primary completion date of 2008-06-28. Its overall enrollment is listed as 11.

Eligibility for participation followed completion of a final visit or, where applicable, an early termination visit in Study Q2788g. Subjects also had to meet this study’s eligibility criteria and consent to take part. The intervention is omalizumab. The study is categorized as single-group, with allocation listed as not applicable and masking listed as none.

Although posted safety counts are divided into two groups, those labels refer to the subjects’ prior assignment in Study Q2788g. The current study description says omalizumab was given to subjects who had previously received placebo as well as those who had previously received omalizumab. The groups therefore do not constitute a concurrent randomized treatment and control comparison in this study. The registry cautions that they are not a like-for-like control comparison.

The primary outcome is serious adverse events through Week 52, measured as participants with an event in the safety-analysis population. The record also lists secondary outcomes involving patient-reported food allergen exposure, reactions assessed by the Ewan Scale, and nonserious adverse events.

Several design details are not reported in the registry record, including the specific eligibility criteria, the methods used to recruit participants, the rationale for the planned enrollment, and details of any protocol amendments. The registry record also does not report the number of participants who completed follow-up or the timing of individual assessments beyond the primary outcome timeframe.

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

Analysis population for the primary outcome, as defined in the registry: Safety-analysis population

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 Serious Adverse Events, measured over Through Week 52.

The primary endpoint counts participants in the safety-analysis population who experienced a serious adverse event through Week 52. The record specifies that events were graded under the National Cancer Institute Common Terminology Criteria for Adverse Events, v3.0. It defines an SAE as an adverse event resulting in death, being life threatening, requiring hospitalization, causing significant disability, resulting in a birth defect, or considered a significant medical event by the investigator.

Serious adverse events are used in safety reporting because the definition focuses on events with serious consequences or significance as judged by the investigator. The endpoint is a participant count, rather than a measure of symptom intensity over time or a count of every event episode. A participant who experiences an event is counted as a participant with an event under the endpoint’s stated measure; the registry record does not provide further counting rules for repeated events.

The endpoint is descriptive in this study. Its value can indicate what was recorded in the safety-analysis population during the stated follow-up, but the design does not make the group counts a randomized comparison of treatment strategies. The registry record does not report an endpoint estimate adjusted for other factors, a confidence interval, or a hypothesis test.

The listed follow-up is through Week 52. The record does not report additional detail about how incomplete follow-up was handled or how the safety-analysis population was defined beyond naming that population.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does a participant count measure?

The primary outcome is a count of participants who experienced at least one serious adverse event during the stated follow-up. This is different from counting all adverse-event episodes: the measure is specified in participants, and the record does not describe a separate episode-level analysis. A participant count can communicate how many people met the endpoint definition in the observed safety population. It does not, without further analysis, characterize event duration, recurrence, severity beyond the SAE classification, or the timing of events within follow-up.

The posted results give group-specific counts and denominators. A count should be read alongside its denominator, since the count alone does not convey how many participants were represented. These denominators describe the groups in the posted safety results; they should not automatically be treated as the full enrolled population. The record does not give an account of any differences between enrollment and the safety-analysis population.

Why does the study design matter for comparison?

A randomized comparison is designed to make treatment groups comparable through assignment within the study, subject to the conduct and limitations of the trial. In this record, allocation is listed as not applicable, masking is listed as none, and the model is single-group. The two safety-result groups are labeled by treatment received in the earlier Study Q2788g, while the current study gives omalizumab to subjects from both prior groups. The registry cautions that the groups are not a like-for-like control comparison.

Consequently, the difference between their posted counts is not a randomized estimate of what would have happened under different current treatments. Prior treatment history, selection into this follow-on study, and other differences between participants could be associated with the observed event counts. The registry record does not report an analysis that addresses such differences. Open-label conduct also means the study is not described as masked; the record does not report whether that influenced event reporting or evaluation.

What does uncertainty mean for sparse safety counts?

In general, a confidence interval describes a range of values compatible with the data under the assumptions of a statistical method. It can help convey how much uncertainty surrounds an estimate. No confidence interval is reported for the serious adverse-event counts in the registry record. Without one, the posted counts remain the direct descriptive evidence, and their precision is not quantified by an interval.

In general, sparse event data can yield unstable estimates: changing the outcome status of a participant can alter the observed count substantially relative to the amount of data. This is a reason to avoid treating a small count as definitive evidence of a low underlying event rate. It does not justify calculating a new estimate from the posted data when the registry record does not report that estimate or its analytic method.

What can planning calculations say?

The record describes a planning illustration based on the observed effect, with a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. The illustration is described as targeting a stated fraction of the observed effect. For time-to-event outcomes, the stated method gives a total number of events using the Schoenfeld approach; other outcomes are expressed as participants per arm.

Such planning calculations are hypothetical illustrations of sample size under their stated assumptions. They are not the observed enrollment, not evidence that the trial had a particular probability of detecting an effect, and not the trial’s own design justification. The registry record does not report a sample-size justification for this study. No planning values are stated in the registry record for this explanation, so no numerical planning estimate can be interpreted.

What do absent analyses imply?

The registry record lists no analyses. That means it does not report a statistical comparison or model for these safety outcomes in the available record. It does not establish that no analyses were conducted outside the registry; it establishes only that analyses are not reported in the registry record. Without a reported analysis plan, test, or interval, the interpretation should remain descriptive and should not imply a prespecified inferential result.

10. Multiplicity, Missing Data and Analysis Populations

The registry record lists several outcomes: serious adverse events, patient-reported food allergen exposure, food-allergic reactions assessed by the Ewan Scale, nonserious food-related adverse events, and other nonserious adverse events. It does not report a multiplicity strategy for handling inference across multiple outcomes. No analyses are listed, so there are no reported outcome-specific hypothesis tests or adjustment procedures to interpret.

Missing-data methods are not reported in the registry record. The record does not state whether any participants missed visits, had incomplete outcome assessments, withdrew, or were excluded from a particular analysis. It also does not describe imputation, censoring, or sensitivity analyses. Those details should not be inferred from the posted denominators.

The primary endpoint identifies the safety-analysis population, but its detailed definition is not reported in the registry record. The record lists overall enrollment as 11 and gives safety-result denominators of 4 and 7 for the two prior-study groups; it does not explain how those counts relate to enrollment or whether any safety observations were unavailable.

These omissions limit the assessment of how completely the posted results represent the intended population and how robust any comparison might be. Since the study is descriptive and no analyses are reported, the prudent interpretation is to retain the stated group counts and avoid assumptions about unreported data handling or multiplicity control.

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 0% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: depression (14.3%), overdose (14.3%).

The primary safety results report serious adverse events through Week 52. The prior-placebo group has 0 of 4 participants listed with an SAE, and the prior-omalizumab group has 1 of 7. The record separately lists other adverse events for 3 of 4 and 6 of 7 participants, respectively. These are group-specific descriptive counts, not a randomized treatment comparison.

The SAE definition includes events resulting in death, being life threatening, requiring hospitalization, causing significant disability, resulting in a birth defect, or judged a significant medical event by the investigator. The record also specifies grading according to NCI CTCAE, v3.0. The listed top serious-event terms are Depression and Overdose, each reported as 14.3%; the registry record does not specify their group attribution in the registry entries. Death counts are not reported in the registry record.

These counts do not establish causation, comparative risk, or the absence of other possible safety concerns. No confidence interval, inferential analysis, or event-level timing is reported. The small denominators and nonrandom group structure make the results most appropriate for cautious description of the recorded events.

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

The result establishes what the registry reports for the serious adverse-event endpoint: 0 of 4 participants in the prior-placebo group and 1 of 7 in the prior-omalizumab group were listed as having an SAE through Week 52. It also reports other adverse-event counts and serious-event terms. These are observations from the study’s safety reporting, not estimates from a controlled comparison of current treatment assignments.

The result does not establish that omalizumab caused or prevented an event. Both groups received omalizumab in the current study, and their labels refer to earlier assignment in Study Q2788g. The registry explicitly warns that the groups are not a like-for-like control comparison. The open-label, single-group design also does not provide the basis for attributing group differences to a current treatment contrast.

Nor does a zero count in one group mean that no serious adverse events can occur in the broader population. The study’s posted group denominator is limited, and the record does not report confidence intervals or other precision estimates. The count should not be treated as a precise estimate of a population rate.

The findings also do not answer the listed secondary questions in detail. Although the record names outcomes concerning food allergen exposure, food-allergic reactions, and nonserious adverse events, the registry entries do not provide results for those measures. The registry record lists no analyses, and does not report missing-data methods, an inferential statistical plan, or the rationale for enrollment.

Overall, the evidence supports a narrow descriptive reading of reported safety events in this follow-on study. Broader conclusions about comparative safety, treatment efficacy, or outcomes in populations beyond the participants represented in the record are not established by these data.

13. Why This Trial Matters Statistically

This trial illustrates why a study’s design and its group labels must be read together. Two groups appear in the posted safety results, but they are defined by treatment history in an earlier study. In the current study, both are described as receiving omalizumab. Treating the labels as if they represented a concurrent randomized treatment and control comparison would misstate the design.

It also demonstrates the difference between a descriptive safety endpoint and a causal treatment estimate. Counts of participants with serious adverse events can document observed events under a stated definition and follow-up period. To estimate a comparative effect, however, a suitable comparison and a reported analysis would be needed. The registry record cautions that the groups are not a like-for-like control comparison and lists no analyses.

The small posted denominators make precision especially important. A count can be reported exactly, while the uncertainty around the population quantity it might reflect remains unquantified when no interval or model is reported. Statistical interpretation should therefore preserve both the observed counts and the limits on what those counts can establish.

Finally, the record distinguishes enrollment, the safety-analysis population, and the group denominators without explaining their relationship. Recognizing that distinction helps prevent unsupported participant accounting. In this study, careful reading means describing the posted results as they are labeled, not filling gaps in the record with assumptions about analysis populations, missing data, or design rationale.

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 study is open-label, is categorized as single-group, and has allocation listed as not applicable. Its two posted safety groups are based on prior assignment in Study Q2788g, not a current randomized allocation. The registry explicitly warns that they are not a like-for-like control comparison. This sharply limits interpretation of any apparent difference between their event counts.

The overall enrollment is listed as 11, while the safety results show denominators of 4 and 7. The registry record does not explain the relationship between enrollment and these safety counts, identify exclusions, or report the number with complete follow-up. The detailed definition of the safety-analysis population is also not reported in the registry record.

The primary outcome is specified through Week 52, but event timing and details of repeated events are not reported. The record does not report confidence intervals, inferential tests, adjustment for potential differences between groups, or a statistical analysis plan. It also does not report methods for missing data or multiplicity.

The record names secondary outcomes but the registry entries available for this analysis do not include their results. It does not report a sample-size justification, interim-analysis plan, or detailed eligibility criteria. Death counts are not reported in the registry record. These limitations mean that the posted safety counts should be interpreted as descriptive observations, with no claim of comparative or causal effect.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: A Study of Xolair in Peanut-Allergic Subjects Previously Enrolled in Study Q2788g — NCT00382148.
• Registry record last updated 2026-06-02; status last verified 2026-05.
• Results first posted 2009-12-15.
• 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

NCT00382148 is a completed, Phase IIb, multicenter, open-label study of omalizumab in peanut-allergic subjects previously enrolled in Study Q2788g. The listed enrollment is 11. The study started in 2006-11, with primary completion on 2008-06-28.

The primary endpoint is the number of participants in the safety-analysis population with a serious adverse event through Week 52, using the stated NCI CTCAE, v3.0 grading and SAE definition. The posted counts are 0 of 4 in the group previously assigned placebo in Q2788g and 1 of 7 in the group previously assigned omalizumab. Other adverse-event counts are also listed.

The current study is not a randomized comparison between these groups; both are described as receiving omalizumab, and the registry cautions against a like-for-like comparison. No analyses are listed. The registry record does not report a statistical plan, missing-data methods, sample-size justification, or detailed accounting of the safety-analysis population.