Academic Achievement in Children With Asthma: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Academic Achievement in Children With Asthma (NCT02228499), a registered phase not stated study. The primary outcome is GPA.

2. Clinical Question

3. Trial Design

This is a cross-sectional observational study, not a randomized clinical trial. The study summary describes recruiting children with and without asthma and collecting information about them at a single time point. The registry lists a survey intervention type, but the survey is a data-collection activity rather than an assigned medical treatment. No allocation method is stated.

The asthma group was to be recruited through emergency departments and the IMPACT DC asthma clinic; controls were to be recruited from an emergency department. The summary describes demographic data collection, asthma-severity information for cases, and requests for parents to mail report cards and standardized test scores to investigators. It also describes multivariable linear and logistic regression as planned approaches for examining associations between asthma and school performance. The registry record does not report whether these planned procedures were completed or which variables were included in any fitted model.

The registry lists enrollment as 66. The primary-outcome description states an intended comparison of 200 children with asthma and 200 without asthma. The record does not explain how this intended enrollment relates to the enrollment figure. There is also a timing inconsistency: the registry lists study start on 2016-12-15 and primary completion on 2017-03-31, while the primary-outcome description refers to report-card collection during 2014. The record does not clarify the discrepancy.

The posted record identifies the study as completed. Completion status does not by itself establish that the primary outcome was analyzed or that results were posted. No randomization, masking, or prespecified analysis details beyond the general regression description are reported.

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.

Before assignment: After participant enrollment the lead author of the study called to obtain report cards. Those participants for which a report card was unable to be obtained was not included in the GPA analysis.

Overall Study

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.

Population: Analysis population was not different from the original assignment.

6. Primary Endpoint

The registry lists the primary outcome as GPA, measured over single time point.

The primary endpoint is GPA, described as a mean measured on an unweighted 0-4 scale at a single time point. GPA is a continuous measure: its numerical value can take a range of values rather than representing a binary event. The stated purpose is to compare GPA between children with asthma and children without asthma as an indicator of school performance.

Using an unweighted GPA makes the outcome a summary of grades without weighting courses by another factor such as course level. The registry’s description does not specify how individual course grades would be converted to GPA, how report cards with different formats would be handled, or how missing report cards would be treated. Those details are not reported in the registry record.

A mean comparison can describe the average outcome in each group, while the spread of individual GPAs helps show how much participants vary within groups. The endpoint record identifies standard deviation as the measure of dispersion, but the posted results do not include group means or standard deviations. Therefore, the record does not show the size or direction of a GPA difference, nor how precisely any difference was estimated.

GPA is an academic measure, not a direct measure of asthma severity or a causal effect of asthma. In this observational design, any group difference could reflect asthma status, other differences between the groups, or a combination. The endpoint alone cannot distinguish among those explanations.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The study summary describes multivariable linear and logistic regression as intended methods. These are general statistical approaches, and the registry record does not establish which analyses were ultimately conducted. It reports no model estimates, standard errors, confidence intervals, or p-values for the primary outcome.

Why use linear regression for GPA?

In general, linear regression models the relationship between a continuous outcome and one or more explanatory variables. For a GPA comparison, asthma status could be represented as a group indicator, and additional measured characteristics could be included as covariates. The coefficient for asthma status would then express the modeled difference in mean GPA between groups, conditional on the covariates in the model. The interpretation depends on how the variables are coded and which participants are included.

Regression adjustment can account for measured characteristics included in the model, but it does not automatically remove confounding. Unmeasured factors, inaccurate measurements, or inappropriate model assumptions may still affect an estimate. Because the covariates and fitted models are not reported in the registry record, the degree of adjustment and the assumptions used cannot be assessed.

What does logistic regression add?

In general, logistic regression is used when an outcome is binary, such as an outcome recorded as present or absent. The study summary mentions logistic regression for school performance, but does not specify which school-performance outcomes would be modeled as binary, how any binary outcome would be defined, or the corresponding results. It should therefore be read as a planned method rather than evidence that a particular logistic analysis was performed.

What does a mean and standard deviation describe?

The primary outcome is a mean of a continuous measure, and standard deviation is named as the dispersion measure. In general, the mean describes the central average, while the standard deviation describes the spread of individual observations around that average. The mean and standard deviation together can help readers understand both a group’s typical value and its variability. Neither is reported for GPA in the posted results, so readers cannot compare the distributions between groups.

A mean difference and its confidence interval would typically be useful for interpreting this kind of comparison. The difference would describe the estimated separation between group means; its interval would convey uncertainty under the analysis assumptions. A p-value, if reported, would address compatibility of the data with a specified null hypothesis, but would not measure the size or practical importance of a difference. None of these primary-outcome statistics appears in the registry record.

Why does over-dispersion matter?

In general, over-dispersion means that observed variability is greater than a statistical model expects. It is especially relevant in count outcomes modeled with distributions that make a particular relationship between the mean and variance. If over-dispersion is ignored, standard errors may be too small and confidence intervals may be too narrow. GPA is described as a continuous outcome, and the registry does not report a count model or a check for over-dispersion. This concept is therefore general background, not a finding about this study.

What can cross-sectional data establish?

In general, a cross-sectional comparison measures exposure or group status and outcomes within a defined study period, rather than assigning a treatment and following a randomized contrast. Such data can describe associations, but temporal ordering and causal attribution may be difficult to establish. This distinction matters because the asthma and control groups were not randomized. Differences in recruitment or other characteristics could contribute to an observed GPA contrast.

The primary endpoint specifies a single time point, and the record describes report-card collection. It does not provide the exact analysis date for each participant, the handling of multiple report cards, or whether all participants contributed a GPA value. Those details would affect interpretation of the analysis population and the precision of estimates.

What do the planning assumptions mean?

In general, a sample-size illustration based on an observed effect is a planning exercise: it shows how a future study’s size might relate to an assumed effect and specified statistical assumptions. The record describes a two-sided significance level of 0.05, equal allocation, and a normal approximation for its planning illustration. It also states that the effect to detect is a stated fraction of the observed effect. Numerical planning estimates are not reported in the registry record. Such illustrations are not observed power, do not establish what the study could detect after completion, and do not replace the primary analysis.

The record does not report a sample-size justification for the study’s own design. It also does not give enough information to reproduce a regression analysis or assess model fit. The summary of intended methods explains the general analytic goal, but the absent model details and outcome results limit statistical interpretation.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists one primary outcome measure, GPA. It does not report whether the investigators tested multiple versions of GPA, examined other academic outcomes as secondary endpoints, or adjusted for multiple comparisons. Although the study summary mentions standardized test scores and school performance more broadly, the registry does not provide results for those measures. Whether multiplicity was addressed is not reported in the registry record.

The record does not describe how missing report cards, incomplete academic records, or missing covariates were handled. It does not state whether analysis used complete cases, imputation, or another approach. The number of participants with a usable GPA is not reported. Therefore, the enrollment figure cannot be treated as the number included in the primary analysis.

Analysis populations are also not defined. The record does not state whether all enrolled participants were included, whether eligibility was reassessed, or whether any participants were excluded from a particular analysis. The adverse-event denominators do not establish the primary-outcome analysis population.

These omissions matter because missingness and selective analysis can influence estimated group differences and their uncertainty. Without a description of the analysis population, missing-data approach, and multiplicity strategy, readers cannot assess whether the reported analyses—if any—followed a prespecified plan. Those details are not reported in the registry record.

11. 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 0% reporting threshold.

The adverse-event record lists zero serious events in the asthma group, with 30 participants at risk, and zero serious events in the controls group, with 36 participants at risk. It also lists zero other events in each group, using the same at-risk counts. No serious-event terms are listed.

These entries are counts recorded in the registry; they are not GPA findings and do not answer the study’s primary question about school performance. The record describes an observational study rather than a randomized treatment comparison, so these safety figures should not be interpreted as evidence about the safety of a treatment. The registry does not report further details about event definitions, ascertainment, or the period over which events were collected.

Zero recorded events means no events are listed in these entries. It does not establish that no health events occurred outside the recorded scope, and it does not provide a comparison of treatment-related risk. The event counts also do not supply information about missing GPA measurements or the number of children included in the primary analysis.

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

The study addresses a question of interest to clinical and education researchers: whether academic performance differs between children with asthma and children without asthma. It identifies unweighted GPA as the primary measure and describes a cross-sectional observational comparison. That design can be used to study an association in the recruited groups, but it does not assign asthma status and cannot by itself establish that asthma caused any academic difference.

The record does not report group GPA values or statistical estimates. It therefore does not show whether average GPA was higher, lower, or similar across the groups, and it does not show how precisely a difference was estimated. The hypothesis that children with asthma would have lower GPA is not a result. No conclusion about the direction, magnitude, or statistical significance of an association can be drawn from the posted primary-outcome information.

The enrollment figure and the adverse-event entries do not fill this gap. They do not provide academic outcome data, and the record does not state how many participants had report cards suitable for analysis. The primary-outcome description also gives a planned enrollment that is not reconciled with the registry’s enrollment figure.

Even if an association were reported, differences in recruitment and other characteristics could contribute to it. The summary mentions multivariable regression, but the actual model and its results are not reported. The record is therefore useful for identifying the study question and intended outcome, but not for estimating the relationship between asthma status and GPA.

13. Why This Trial Matters Statistically

This study is statistically notable because it frames academic performance as a measurable outcome in a population with a chronic childhood condition. The registry identifies a direct, interpretable endpoint—unweighted GPA—and describes a comparison between children with asthma and children without asthma. A clear outcome definition helps readers understand what kind of evidence would address the research question.

At the same time, the observational design makes careful interpretation important. The groups were not described as randomized, and their recruitment sources differ: children with asthma were to come from emergency departments and an asthma clinic, while controls were to come from an emergency department. Differences in who enters each group can affect a comparison, even when regression adjustment is planned. The record does not report enough detail to evaluate those issues or determine what adjustment was made.

The case also illustrates the difference between a registered research question and a posted result. The record names a primary endpoint and describes planned statistical methods, yet it does not provide the GPA estimates needed to answer the question. Enrollment and completion status cannot substitute for outcome reporting. Without group summaries and uncertainty estimates, readers cannot judge the size or precision of an association.

Finally, the difference between the stated intended enrollment and the recorded enrollment, and the inconsistent timing descriptions, make transparent reporting especially important. Clarifying the analyzed population, missing-data handling, model specification, and primary results would be necessary for a fuller statistical assessment. The registry record as posted supports an account of the research aim, not a conclusion about its outcome.

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.

Several limitations are specific to the available record. First, the primary outcome is named, but no GPA results are posted. There are no group means, standard deviations, estimated contrasts, confidence intervals, or p-values with which to assess direction, magnitude, or precision.

Second, the population descriptions are not fully aligned. The study summary describes middle-school children in grades 6-8 during the 2013-2014 school year, while the primary-outcome description refers to grades 3-8. The record does not explain which population was ultimately enrolled or analyzed. It also lists study start on 2016-12-15 and primary completion on 2017-03-31, while the endpoint description refers to report-card collection in 2014. The timing discrepancy is not clarified.

Third, the primary-outcome description states an intended enrollment of 200 children with asthma and 200 controls, whereas the registry lists enrollment as 66. The relationship between these figures is not reported. The record does not state how many participants contributed report cards or usable GPA values, whether data were missing, or how missingness was handled.

Fourth, the summary names multivariable regression but does not report model details, selected covariates, diagnostics, or results. Recruitment from different clinical settings may also produce groups with different characteristics; the record does not provide enough information to assess comparability. These limitations prevent evaluation of both the primary association and the robustness of any analysis.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Academic Achievement in Children With Asthma — NCT02228499.
• Registry record last updated 2019-05-07; status last verified 2019-02.
• Results first posted 2019-05-07.
• 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

The registry record describes a completed cross-sectional observational study of school performance in children with and without asthma. It lists enrollment as 66 and identifies unweighted GPA on a 0-4 scale at a single time point as the primary outcome. The study summary describes planned multivariable linear and logistic regression.

The record does not report GPA group summaries, an estimated association, uncertainty measures, or primary-outcome analysis results. It also does not explain the relationship between the recorded enrollment and the intended enrollment described for the primary outcome. The adverse-event entries list zero serious events and zero other events in each group. The available record defines the research question and intended approach, but does not provide the findings needed to answer the primary question.