Allergens in Inner-City Schools and Childhood Asthma: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Allergens in Inner-City Schools and Childhood Asthma (NCT01756391), a registered phase not stated study. The primary outcome is Maximum Symptom Days/14 Days.

2. Clinical Question

The stated project goal is to understand exposure risk factors specific to classrooms. The rationale is that elementary school children spend 6 to 10 hours a day in school, much of it in one classroom, and that classroom exposures might be a target for reducing asthma morbidity. The registry summary also places the topic in the context of asthma-related school absence. These statements describe the project’s motivation, not findings from its analysis. Because results and analytical comparisons are not reported, the record cannot establish how exposure relates to the primary outcome.

3. Trial Design

Allergens in Inner-City Schools and Childhood Asthma is registered as an observational cohort sponsored by Boston Children's Hospital. The registry lists enrollment of 351 and a status of completed. The study start is recorded as 2008-03, and primary completion as 2014-10. These dates describe the registered study timeline; they do not indicate when individual children were followed or how long each participant contributed data.

The study concerns school and home allergen exposure, allergy sensitization, and asthma-related symptoms. The primary outcome population is defined as those with appropriate follow-up and the relevant exposure and sensitization data. The registry does not report how exposure or sensitization was measured, when measurements were taken, or how many enrolled participants satisfied this population definition.

This is not a randomized comparison. Allocation is not stated, and the registry warns that the arms are not a like-for-like control comparison. The record does not describe assigned treatments, a control intervention, or a prespecified exposure contrast. Consequently, the study should be read as an observational investigation rather than as a controlled estimate of an intervention effect. Differences between any groups could reflect differences in who was observed or in their exposures, rather than an effect caused by a study assignment.

The registry lists 14 outcome measures, including the primary symptom measure and secondary asthma-related outcomes. It does not report the analysis population for each outcome beyond the primary population description, nor does it give a statistical analysis plan. Although the record is marked completed, it contains no analysis entries or numerical primary outcome results. Details such as participant flow, follow-up completeness, and the handling of exposure groups 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

Analysis population for the primary outcome, as defined in the registry: Those with appropriate follow up and school/home allergen exposure data and allergy sensitization data

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 Maximum Symptom Days/14 Days, measured over 14 days.

The primary endpoint, Maximum Symptom Days/14 Days, is a continuous measure reported as a mean with standard deviation. It represents the largest value among three symptom-related counts over a 14-day period: days with wheezing, chest tightness, or cough; nights with disturbed sleep due to asthma; and days when asthma caused the child to slow or discontinue play. The unit is days.

Using the largest of several counts gives a single measure that reflects the most prominent of the listed symptom domains for a child during the observation period. It therefore differs from an endpoint that adds all symptom domains together: the registry definition selects the largest value rather than describing a total across symptoms. The record does not explain why this particular summary was chosen, whether it was validated, or how ties among domain counts were handled.

A fixed observation period makes the symptom measure interpretable over a defined span, while a mean describes the average level in the analysis population and a standard deviation describes variation among observations. Those are general properties of these summaries; they do not establish what the observed average or variability was in this study. The registry record does not report either value, an effect estimate, or a comparison for the primary endpoint.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry identifies the primary measure as continuous and specifies a mean and standard deviation as its summary statistics. In general, a mean describes the center of observed values, while a standard deviation describes their spread around that center. These summaries are useful for describing an outcome across participants, but they do not by themselves describe a difference between groups. To interpret a comparison, readers would also need the group-specific results or a contrast, along with information about uncertainty. Such results are not reported in the registry record.

What does the primary outcome summarize?

The endpoint selects the largest of the listed symptom counts over 14 days. It is not defined as the sum of symptom days, nights of disturbed sleep, and restricted-activity days. This distinction matters because a maximum emphasizes the most prominent domain for each participant rather than accumulating burden across domains. The record does not explain the rationale for choosing the maximum, how each component was collected, or how missing component values were handled.

As a general statistical point, symptom counts collected over a fixed observation window have a restricted range and may not behave like measurements that can take any value on a continuous scale. Means and standard deviations can still describe such data, but their adequacy for a particular analysis depends on the distribution and the study question. The registry record does not report distributional checks, a model, or a rationale for the analysis method.

What would an estimate and confidence interval add?

In general, an effect estimate would quantify the contrast or association being studied, while a confidence interval would show the range of values compatible with the data under the analysis assumptions. A narrow interval indicates greater precision than a wide interval, but neither an interval nor a point estimate establishes causation in an observational study. The registry record includes no primary outcome estimate or confidence interval, so neither magnitude nor precision can be assessed from the posted results.

A p-value, in general, measures how surprising data at least as incompatible with a specified null hypothesis would be under that hypothesis and the model assumptions. It does not measure the probability that the null hypothesis is true, nor does it describe the size or practical importance of an association. No p-value or test result is reported in the registry record. Without the analysis details and estimates, statistical significance cannot be evaluated.

How should planning illustrations be read?

Any sample-size illustration based on an observed effect is a planning exercise, not an observed trial result and not observed power. The stated assumptions for such illustrations are a two-sided significance level of 0.05, equal allocation between arms, a normal approximation, and an effect set to a stated fraction of the observed effect. The record does not provide a primary outcome effect estimate or analysis from which to verify an observed effect. These assumptions therefore should not be read as the study’s own design justification, and they do not establish that the observational groups were balanced or randomized. The record does not report the study’s sample-size justification.

In general, sample-size planning depends on the outcome, target contrast, variability, allocation, and chosen statistical assumptions. Changing the assumed effect changes the planning question. A smaller target effect generally requires more information to detect than a larger target effect, all else equal; that is a general relationship, not a result from this cohort. The planning assumptions do not substitute for reported participant counts in the primary analysis, which are not reported in the registry record.

What analysis details remain unknown?

The registry does not report whether the primary analysis was adjusted, which covariates might have been used, whether repeated observations were modeled, or how clustering by school or classroom was handled. These are potential considerations in general for observational data gathered in school settings, not claims about the methods used in this study. The analysis model, treatment of continuous measures, missing-data method, and any sensitivity analyses are not reported in the registry record. No interim analyses are reported in the registry record. With no analysis entries or numerical estimates, the actual statistical approach and its assumptions cannot be assessed.

10. Confidence Intervals for Each Arm

No two-arm comparison is shown for this trial, but each arm's mean can be given with a t-based 95% confidence interval computed from the posted mean, spread and number of participants.

R code and output

arm <- c("Observational Cohort")
n   <- c(284)
m   <- c(2.7)
sp  <- c(4)
sd  <- sp      # posted standard deviations
for (i in seq_along(n)) {
  se <- sd[i] / sqrt(n[i]); h <- qt(0.975, n[i] - 1) * se
  cat(sprintf("CARM|%s|%d|%.3f|%.3f|%.3f|%.3f\n", arm[i], n[i], m[i], sd[i], m[i] - h, m[i] + h))
}

CARM  Observational Cohort  284  2.700  4.000  2.233  3.167

11. Multiplicity, Missing Data and Analysis Populations

The registry lists 14 outcome measures. It identifies one primary outcome and names secondary outcomes covering activity limitation, exercise-induced symptoms, cough without an upper respiratory infection, nights of asthma-related waking, hospitalizations, emergency department visits, unscheduled physician or health-care visits, and prednisone bursts. A study that examines multiple outcomes can encounter multiplicity: the more comparisons made, the greater the chance that some results may appear notable by chance alone. As a general statistical matter, plans for prioritizing outcomes or controlling multiplicity help readers interpret a collection of tests. Such plans are not reported in the registry record.

The record does not report which outcomes were analyzed, whether any adjustment for multiple testing was used, or whether analyses were prespecified. There are no analysis entries. It is therefore not possible to determine whether the primary outcome was analyzed as planned, how secondary findings were interpreted, or how any selective reporting concerns were addressed.

Missing-data details are also not reported. The primary analysis population requires appropriate follow-up and school and home allergen exposure and sensitization data, but the record does not state how many participants had all those data, how much follow-up was incomplete, or why any data were missing. It does not describe imputation, exclusion, or other missing-data methods. The registered enrollment of 351 is not a substitute for an analysis-specific denominator.

The registry does not describe whether the analysis population was defined before results were reviewed, whether participants were excluded from particular outcomes, or how incomplete outcome measurements were handled. Those details affect how representative an analyzed group may be and how robust estimates are to missingness. In their absence, the scope of any outcome estimate cannot be evaluated; moreover, numerical outcome estimates are not reported in the registry record.

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 0% reporting threshold.

The registry’s observational-cohort safety entry lists 351 participants at risk for serious adverse events and 0 affected. It also lists 351 at risk for other adverse events and 0 affected. These are the counts recorded in the safety fields; they do not provide event-level descriptions or a comparison between randomized treatment groups. Because the study is an observational cohort and no assigned intervention is reported, the counts should not be interpreted as a randomized estimate of treatment-related risk.

The deaths field is null. That is not a reported count of zero deaths: death information is not reported in the registry record. No top serious adverse event terms are listed. The record does not explain the observation period for safety reporting, how events were collected, or whether the counts cover every enrolled participant over the same duration. A zero in the affected field means that the registry entry reports no affected participants for that field; it does not, on its own, establish that no events occurred outside the recorded scope or reporting period.

These safety fields should be kept separate from the symptom outcome measures. They do not provide evidence about the primary endpoint or about the relationship between classroom exposures and asthma symptoms. The registry record offers no further safety-analysis detail.

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

The registry record gives a clear description of the question’s setting and the intended primary symptom measure. It concerns allergen exposures in inner-city schools and childhood asthma, and defines maximum symptom days using symptom, sleep, and activity counts over 14 days. It also identifies a population requiring follow-up and exposure and sensitization data. These details help readers understand what the study sought to measure.

They do not show what the study found. No numerical primary or secondary outcome results, effect estimates, confidence intervals, or p-values are reported in the registry record. The record therefore cannot establish whether exposure was associated with more or fewer symptoms, whether groups differed, or how precisely any association was estimated. Absence of a posted estimate is not evidence that there was no association.

The observational design is another important boundary. Allocation is not stated, and the registry cautions that arms are not a like-for-like control comparison. Even if an association estimate were available, interpretation would require attention to how participants and exposure groups differed and to the analysis used. Those details are not reported. A causal effect of reducing classroom allergens cannot be inferred from the stated project goal or from the fact that allergen exposure was studied.

The project’s rationale is that classrooms may be relevant settings for understanding exposure risks, given how much time children spend there. That rationale explains why the topic may matter, but it is not a result. The registry’s completed status likewise does not substitute for posted findings. The defensible conclusion from the record is that the study was registered as an observational cohort with a specified symptom endpoint and a reported enrollment of 351, while its outcome analyses are unavailable in the registry record.

14. Why This Trial Matters Statistically

This study is statistically notable for the distinction between a clinically motivated question and the evidence needed to answer it. The registry sets out to understand classroom-specific allergen exposure risks for children with asthma, and specifies a symptom endpoint combining the largest count across symptom, sleep, and activity domains. That definition makes the outcome’s construction important: it is a maximum, not a total across all listed domains.

The primary outcome population also illustrates why enrollment and analysis denominators are not interchangeable. The registry reports enrollment of 351, while primary analyses are defined for participants with appropriate follow-up, exposure data from school and home, and allergy sensitization data. The number satisfying those conditions is not reported. Without that denominator and the associated results, readers cannot assess how much information contributed to the primary endpoint.

Design matters as much as measurement. The cohort is observational, allocation is not stated, and the record cautions against treating the arms as a like-for-like control comparison. Statistical adjustment can sometimes account for measured differences, but it cannot automatically eliminate bias from unmeasured differences; the record does not say whether adjustment was used. This is a general issue in observational analysis, not a claim about a specific bias found in this study.

Finally, the record lists 14 outcomes without reporting analyses or multiplicity handling. Outcome definitions and a completed status are useful registry information, but they cannot replace effect estimates and uncertainty. The study therefore highlights why transparent reporting of analysis populations, methods, and results is essential to judge what an observational clinical study can support.

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 most important limitation for interpreting this record is the absence of numerical outcome analyses. Although the study is marked completed and identifies a primary endpoint, the registry record does not report its mean, standard deviation, group contrast, or uncertainty. No conclusion about the magnitude or direction of an association can be drawn from the available entries.

The primary outcome population has additional data requirements beyond enrollment, but the number meeting them is not reported. Participant flow, follow-up completeness, and outcome-specific denominators are also not reported in the registry record. This prevents assessment of how much of the enrolled cohort contributed to the endpoint and whether missing follow-up could affect interpretation.

Exposure measurement and comparison details are not reported. The record does not specify how classroom or home allergen exposure was assessed, how sensitization was determined, or how exposure groups were constructed. Allocation is not stated, and the registry cautions that the arms are not a like-for-like control comparison. Thus, the underlying contrast and potential differences between groups cannot be evaluated.

Statistical methods are not described in sufficient detail to assess model choice, adjustment, clustering, missing-data handling, or sensitivity analyses. The registry also does not report a sample-size justification or multiplicity plan. These omissions are especially relevant because the record lists 14 outcome measures. They are limitations of the information available in the registry record and should not be mistaken for proof that a particular method was or was not used outside that record.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Allergens in Inner-City Schools and Childhood Asthma — NCT01756391.
• Registry record last updated 2014-12-08; status last verified 2014-12.
• Results first posted 2014-12-08.
• 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

The registry identifies NCT01756391 as Allergens in Inner-City Schools and Childhood Asthma, an observational cohort sponsored by Boston Children's Hospital. It lists enrollment of 351, a start date of 2008-03, primary completion of 2014-10, and status completed. Asthma is the listed condition.

The primary outcome is maximum symptom days over 14 days, summarized as a mean with standard deviation. The outcome population requires appropriate follow-up and school and home allergen exposure and sensitization data. The record lists 14 outcome measures, including secondary asthma-related symptoms and health-care use.

Allocation is not stated, and the registry warns that the arms are not a like-for-like control comparison. No analysis entries or numerical outcome results are reported in the registry record. Safety fields list 0 affected for serious and other adverse events, while the deaths field is not reported.