Biomarker-based Cockroach Sublingual Immunotherapy Study (BioCSI): Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Biomarker-based Cockroach Sublingual Immunotherapy Study (BioCSI) (NCT00829985), a randomized phase 1, phase 2 study. The primary outcome is Difference in German Cockroach-Specific Serum IgE Over Time.

2. Clinical Question

This was a pilot study, with 54 participants enrolled overall according to the registry. The available arm-level primary outcome values are based on 23 participants in the extract group and 25 in the placebo group. These endpoint counts are not the same as the safety-population counts described elsewhere in the record, so they should be interpreted in the context of the outcome being reported rather than treated as a single universal analysis population.

The study’s central question is about change in a cockroach-specific antibody marker, not a direct measure of symptoms, asthma control, allergic rhinitis severity, or prevention of disease. The registry lists adverse events and additional immune-marker outcomes as secondary outcomes, but numerical results for those outcomes are not reported in the registry record. The primary comparison therefore addresses a biological response over the treatment period, while leaving clinical effects and the broader safety profile insufficiently characterized in the posted outcome results.

3. Trial Design

BioCSI is listed as a randomized, double-masked, parallel-group study, with phase classifications of Phase 1 and Phase 2. The registry identifies the National Institute of Allergy and Infectious Diseases as the sponsor and records the study as completed. It lists enrollment as 54. The study began in 2009-01, and primary completion was recorded as 2009-12.

Participants with German cockroach allergy and mild to moderate asthma, perennial allergic rhinitis, or both received either glycerinated German cockroach allergenic extract or placebo under the tongue. Both were administered daily, and the described treatment course and study duration were 6 months. The registry describes the extract as concentrated, at 1:20 weight per volume, with 50% glycerin. Some arm-description text is truncated in the registry record, so details beyond the visible description are not reported in the registry record.

Randomization supports a comparison between assigned groups, while masking is intended to reduce the influence of treatment knowledge on participant behavior, care, and outcome assessment. The record does not report the randomization sequence method, allocation concealment procedures, or which people were masked. The parallel-group structure means the groups were followed as separate assigned groups rather than in a crossover design.

The primary outcome is the difference in German cockroach-specific serum IgE over time, expressed through a ratio of geometric means for baseline versus post-baseline values. It is measured from baseline through 6-months of treatment. The primary analysis population is identified as intent-to-treat. A mixed models analysis is reported for the primary between-group comparison. Details of the model specification, covariates, repeated-measures structure, handling of missing observations, and analysis time points are not reported in the registry record.

Four secondary outcomes are listed: German cockroach-specific serum IgG4 over time, IgE fragment antibody binding activity at two cockroach allergen extract concentrations, and the percent of participants with adverse events. The registry record does not report numerical results for these secondary outcomes.

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: Intent-to-treat

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 Difference in German Cockroach-Specific Serum IgE Over Time, measured over Baseline through 6-months of treatment.

The primary endpoint concerns German cockroach-specific serum immunoglobulin E, or IgE, over the treatment period. The registry defines the outcome as the ratio of geometric means for baseline IgE versus post-baseline IgE. It describes the result as an indicator of immune modulation over time, while explicitly noting that its clinical significance is unclear. The reported unit is a ratio, and uncertainty is expressed with a 95% confidence interval.

A geometric mean is a way of summarizing measurements when their distribution is better considered on a multiplicative scale. Ratios are also naturally interpreted multiplicatively: they describe how one summarized level relates to another, rather than an absolute difference in the original measurement units. The direction and clinical implications of a change depend on how the ratio is defined and on the role of the marker in the disease process. The registry’s wording describes baseline versus post-baseline values, but does not provide enough detail to translate the marker result into a clinical benefit or harm.

Serum IgE is used as a biological marker of immune response to German cockroach allergen. That makes it relevant to a study investigating immunotherapy, but it is not itself a direct measure of symptoms, function, asthma exacerbations, or rhinitis burden. The registry does not report a threshold for a clinically meaningful change in IgE, nor does it establish that a change in this marker predicts a patient-important outcome. Accordingly, the endpoint can describe a measured immune response, but it cannot on its own establish how participants felt or functioned.

The primary outcome timeframe is baseline through 6-months of treatment. The registry labels its population intent-to-treat, although details of how that population was handled in the mixed models analysis are not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

Clinical trial results can be summarized in more than one way. The primary outcome is presented as arm-level ratios of geometric means, while the reported between-group test is described as a mixed models analysis with a risk ratio on the log scale. These are related descriptions of the study outcome, but they answer questions at different levels: the arm summaries describe each group’s reported ratio, while the model-based result estimates a comparison between groups using the stated analysis.

What does a ratio mean?

A ratio compares quantities multiplicatively. A ratio of 1 represents equality on the ratio scale; values on either side represent different relative levels. For a geometric-mean outcome, the ratio expresses a multiplicative relationship between summarized measurements. This differs from an arithmetic difference, which describes an absolute change in the original units. The endpoint’s stated unit is a ratio, so its interpretation should remain on that scale unless the report provides a justified translation into another measure.

The registry describes the primary outcome as baseline German cockroach-specific serum IgE versus post-baseline IgE, and gives a ratio of geometric means for each arm. The reported arm values are 2.16 for the extract group and 1.12 for placebo. Their intervals reflect uncertainty in those arm summaries. They do not by themselves provide the formal uncertainty for a between-group comparison; that comparison is given separately by the mixed models analysis.

Why use geometric means?

General statistical explanation: biological measurements may be skewed or behave more naturally as multiplicative quantities. A geometric mean can summarize measurements on a logarithmic scale and then be interpreted back on the original multiplicative scale. Modeling a logarithm can also make some analytical assumptions more plausible, such as a more symmetric distribution of residual variation. Whether those assumptions were appropriate in this study cannot be assessed from the registry record because distributional checks and model details are not reported.

What does the confidence interval convey?

A confidence interval gives a range of estimates compatible with the observed data and the model at its stated confidence level. In repeated use under the method’s assumptions, the interval procedure has a specified coverage property. It does not assign a probability that a particular fixed value is true, and it does not account for every possible source of bias or model misspecification. The primary arm intervals are reported at the 95% level, as is the sponsor’s between-group interval.

The sponsor’s interval for the risk ratio, log, is 1.51 to 2.45. Because this interval lies above 1, it is inconsistent with a no-difference ratio of 1 under the fitted model’s interval procedure. That reading is statistical, not clinical: the registry states that the clinical significance of the immune-marker result is unclear. The interval also does not replace reporting of model assumptions, analysis details, and missing-data handling.

What does the p-value add?

The reported p-value is p < 0.001. In general, a p-value describes how unusual results at least as incompatible with the null hypothesis would be if that hypothesis and the statistical model were correct. It is not the probability that the null hypothesis is true, nor is it a measure of the size or importance of an effect. A small p-value can support evidence against a null comparison while leaving clinical meaning, bias, and generalizability unresolved.

Why might a mixed model be used?

General statistical explanation: mixed models can represent correlated or repeated measurements from the same participant, rather than treating every measurement as independent. They can estimate patterns over time and compare groups while accounting for within-participant dependence. Their behavior depends on the model’s fixed and random effects, covariance structure, link or transformation, included visits, and assumptions about missing observations. The registry names a mixed models analysis but does not report those specifications, so it is not possible to evaluate the exact model construction from the posted record.

Over-dispersion is a general concern when count data vary more than a chosen model expects. A model that fails to account for extra variability can produce uncertainty estimates that are too narrow. The primary endpoint is a ratio of geometric means rather than a count outcome, and the record does not report an over-dispersion assessment. This general issue should not be mistaken for a reported problem with this analysis.

What are planning calculations for?

Sample-size illustrations are planning tools, not observed trial results and not observed power. The stated planning assumptions use the observed effect, two-sided significance level 0.05, equal allocation between two arms, and a normal approximation; the effect to detect is a stated fraction of the observed effect. Such illustrations describe what a future design might require under those assumptions. They do not show that the completed pilot study had a particular probability of detecting an effect, and they do not replace the trial’s own design justification. A sample-size justification is not reported in the registry record.

The record’s statistical information is incomplete for a full independent appraisal. It does not report the model specification, multiplicity strategy, interim analysis plan, sample-size justification, or detailed missing-data approach. These gaps limit assessment of how robust the estimate is to analytical choices, even though the sponsor’s reported primary analysis and its uncertainty are available.

10. Analyses Reported by the Sponsor

The sponsor’s own primary comparison is reported as a mixed models analysis. It gives a risk ratio, log, of 1.92, with a 95% confidence interval from 1.51 to 2.45 and p < 0.001. The arm-level summaries report geometric-mean ratios of 2.16 for extract and 1.12 for placebo. The model-based between-group estimate is the sponsor’s stated inferential result; the arm summaries are descriptive outcome values and should not be substituted for that comparison.

The registry record does not report an independent recalculated estimate for the primary comparison. It therefore does not offer a second model-based result to reconcile with the sponsor’s analysis. The registry’s discrepancy indicator is false, so there is no identified conflict between a recalculation and the sponsor’s result. If a discrepancy were present, the sponsor’s own analysis would take precedence, but no such discrepancy is indicated.

The reported p-value and confidence interval provide evidence on the model’s ratio scale, subject to the assumptions and specifications of the mixed models analysis. Those details are not reported in the registry record. The result should not be read as an estimate of symptom improvement or as proof that the measured immune-marker change has clinical significance; the registry explicitly leaves that significance unclear.

11. Multiplicity, Missing Data and Analysis Populations

The registry lists a primary endpoint and four secondary outcomes. These cover German cockroach-specific serum IgE, German cockroach-specific serum IgG4, IgE fragment antibody binding activity at 30 micrograms/mL and 60 micrograms/mL cockroach allergen extract, and the percent of participants with adverse events. Only the primary outcome has a reported numerical comparison in the record. Numerical results for the secondary outcomes are not reported in the registry record.

When several outcomes are tested, the chance of obtaining at least one apparently unusual result can increase if each test is interpreted without accounting for the collection of tests. General statistical practice may address this through a prespecified hierarchy, adjustment, or a clearly exploratory interpretation. The registry record does not report a multiplicity strategy, so it is not possible to determine whether or how the primary and secondary analyses were intended to be interpreted together.

The primary population is identified as intent-to-treat. The record does not explain the precise analysis set, how participants with missing measurements were handled, or whether all randomized participants contributed to the mixed models analysis. The arm-level primary outcome lists 23 participants in the extract group and 25 in the placebo group. These are not necessarily enrollment totals or safety denominators. The registry does not report reasons for missing outcome data or sensitivity analyses that test the effect of missingness assumptions.

For safety, the record gives at-risk counts of 28 for extract and 26 for placebo for serious adverse events, and separate at-risk counts for other adverse events. Those safety counts differ from the primary outcome counts. The record does not explain the population differences, so they should be interpreted only for the corresponding safety summaries.

Interim analyses, a sample-size justification, and a detailed statistical analysis plan are not reported in the registry record. Their absence limits evaluation of prespecification and analysis flexibility. It does not establish that such procedures did or did not occur; it means the registry record does not report them.

12. 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: anaphylactic reaction (3.8%), urticaria (3.8%), scapula fracture (3.6%).

The safety record lists 28 participants at risk for serious adverse events in the extract group and 26 in the placebo group. It reports one affected participant in each group. The record also lists 28 and 26 participants at risk, respectively, for other adverse events, with 25 and 23 affected. These are separate safety summaries. They should not be combined with the primary endpoint counts, which are 23 and 25.

The listed serious adverse event terms are anaphylactic reaction at 3.8%, urticaria at 3.8%, and scapula fracture at 3.6%. The record does not provide enough detail in the posted information to determine how those terms map to each treatment group, whether terms refer to participants or events, or what attribution was made. These percentages should therefore be read as registry-listed serious adverse event terms, not as a complete comparative risk analysis.

Deaths are not numerically reported in the record. The absence of a reported value is not evidence that no deaths occurred. Details such as event timing, severity criteria, causality assessment, withdrawals due to adverse events, and exposure-adjusted rates are not reported in the registry record. With a pilot study and outcome-specific counts, these figures are descriptive and do not establish a reliable comparative safety profile.

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

The primary finding is a difference between the extract and placebo groups on the reported German cockroach-specific serum IgE ratio scale. The sponsor’s mixed models analysis reports a risk ratio, log, of 1.92, with a 95% confidence interval from 1.51 to 2.45 and p < 0.001. The arm-level geometric-mean ratios are 2.16 for extract and 1.12 for placebo. These results describe an immune-marker outcome over baseline through 6-months of treatment.

What the result does mean is that the sponsor-reported model found evidence of a between-group difference on its specified statistical scale. The result is consistent with a change in the measured marker over time that differed between the randomized groups, under the model’s assumptions. The registry describes the endpoint as an indicator of immune modulation.

What it does not mean is that symptoms improved, asthma or rhinitis was controlled, disease was prevented, or participants experienced a clinically meaningful benefit. The registry itself says that the clinical significance of the primary outcome is unclear. The primary endpoint is an antibody marker, not a direct clinical outcome, and the record does not establish that a change in this marker predicts a patient-important effect.

The result also does not establish a complete safety profile. Safety counts and serious adverse event terms are reported, but the record does not provide enough detail to interpret comparative risks fully. Numerical results for the listed secondary immune-marker and adverse-event percentage outcomes are not reported in the registry record.

Finally, the finding should be understood in the setting of a pilot study and the details available in the registry. The record does not report the mixed-model specifications, a multiplicity strategy, a missing-data approach, or the sample-size justification. These omissions do not negate the reported analysis, but they limit how fully its robustness and clinical implications can be assessed.

14. Why This Trial Matters Statistically

This trial is statistically interesting because it places a biological marker at the center of a randomized, double-masked comparison. The primary outcome uses a ratio of geometric means, and the sponsor reports a mixed models analysis. Understanding the distinction between group summaries and a model-based between-group comparison helps prevent readers from treating each arm’s value as though it were itself the comparative effect.

The record also illustrates why statistical evidence and clinical interpretation are separate tasks. A confidence interval that excludes 1 and a reported p-value of p < 0.001 provide evidence against a null ratio under the model. But the registry explicitly states that the clinical significance of the IgE result is unclear. A statistically detectable marker difference is not automatically a meaningful difference in symptoms or function.

The study’s pilot designation makes transparent reporting especially important. The registry identifies the primary population and names a mixed models analysis, but does not report details of the model, missing-data procedures, multiplicity strategy, or sample-size justification. These omissions constrain independent assessment and make it important to avoid overstating what the outcome establishes.

Finally, the record distinguishes outcome-specific populations: the primary result and safety summaries have different reported counts. Reading each denominator in relation to its outcome avoids treating all reported counts as if they referred to the same analysis set. The study therefore serves as an example of how interpretation depends not only on an estimate and p-value, but also on endpoint relevance, analysis definitions, uncertainty, and the completeness of registry reporting.

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 primary endpoint is a biomarker, and the registry states that its clinical significance is unclear. No numerical clinical outcome results for symptoms, asthma control, or rhinitis severity are reported in the registry record. The observed primary comparison therefore cannot be translated into a direct estimate of clinical benefit from the information available.

The record identifies a mixed models analysis but does not provide its specification, covariates, correlation structure, visit-level analysis details, or missing-data assumptions. It also does not report diagnostic checks or sensitivity analyses. This prevents a full independent assessment of model fit and robustness. The record does not report a multiplicity strategy despite listing four secondary outcomes.

The primary endpoint counts are 23 in the extract group and 25 in the placebo group, while safety populations have different at-risk counts. The registry does not explain the difference or report reasons for missing outcome data. The primary population is labeled intent-to-treat, but operational details of that analysis population are not reported in the registry record.

The arm descriptions are partially truncated, limiting the detail available about treatment administration and the preliminary period. The registry lists serious adverse event terms and percentages, but does not report enough detail to assign those terms to a treatment arm or interpret them as a comprehensive comparative safety analysis. Deaths are not numerically reported.

Finally, the study is identified as a pilot, and its enrollment is 54. The registry does not report the sample-size justification or any interim analysis plan. The record’s limitations are limitations of the information reported; they do not establish that omitted procedures were absent or that the analyses were necessarily invalid.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Biomarker-based Cockroach Sublingual Immunotherapy Study (BioCSI) — NCT00829985.
• Registry record last updated 2017-03-21; status last verified 2017-02.
• Results first posted 2013-03-08.
• 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

BioCSI is a completed randomized, double-masked, parallel-group pilot study of daily sublingual glycerinated German cockroach allergenic extract versus placebo in adults with German cockroach allergy and mild to moderate asthma, perennial allergic rhinitis, or both. The registry lists enrollment as 54 and identifies the National Institute of Allergy and Infectious Diseases as sponsor.

The primary outcome is German cockroach-specific serum IgE over baseline through 6-months of treatment, expressed as a ratio of geometric means. The sponsor’s mixed models analysis reports a risk ratio, log, of 1.92, with a 95% confidence interval from 1.51 to 2.45 and p < 0.001. The registry states that the clinical significance of this immune-marker outcome is unclear.

Four secondary outcomes are listed, but their numerical results are not reported in the registry record. The record also lacks details needed to fully assess the model, missing-data handling, multiplicity, and sample-size justification. Safety summaries are reported with outcome-specific counts and serious adverse event terms, but do not provide a complete comparative safety interpretation.