This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record. Numerical trial results on this page are restricted to the results posted in the ClinicalTrials.gov record; calculations added by Clinical Biostats are labelled as such.
1. Trial at a Glance
This page covers the registry results for Screening Scottish Swimmers for Asthma and Rhinitis (NCT00831428), a registered phase not stated study. The primary outcome is Tidal Nitric Oxide.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT00831428 |
| Phase | Phase not stated |
| Condition | Asthma, Rhinitis |
| Allocation | Not Stated |
| Design model | Not Stated |
| Masking | Not Stated |
| Enrollment | 97 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Brian J Lipworth |
| Results posted | Yes |
2. Clinical Question
Population
The Scottish National and District swimming teams were the intended population for screening. The registry records enrollment of 97 participants and describes analysis of data from all participants for the primary outcome. It does not report participant characteristics, the number who completed each assessment, or how many were included in each analysis.
Intervention
This was a screening study, not a treatment study. The registry summary describes screening with mannitol challenge and sport-based exercise challenge. The intervention entry is listed as no intervention. Other recorded assessments include nasal nitric oxide, skin prick testing, and mini nasal lavage.
Comparator
The registry lists a Scottish swimming team arm, but does not describe a like-for-like control group. The study is not a randomized comparison, and allocation is not stated. The challenges are assessment methods; the record does not describe them as treatment arms or establish a controlled comparison between them.
Primary question
The primary outcome is tidal nitric oxide, measured in ppb, with the stated assessment before entering the pool and on exiting the pool. The wider study aim was to screen swimmers for asthma and rhinitis using mannitol and sport-based exercise challenge. The measured tidal nitric oxide values, confidence interval, and screening findings are not reported in the registry record.
3. Trial Design
NCT00831428 is a completed pilot study titled “Screening Scottish Swimmers for Asthma and Rhinitis.” Its official title describes a study intended to identify the prevalence of exercise-induced asthma and rhinitis in Scottish swimmers, using mannitol challenge as a screening tool. The registry summary also describes sport-based exercise challenge. The record identifies asthma and rhinitis as the conditions of interest.
The study began in 2009-02, with primary completion in 2009-05, and its status is COMPLETED. Enrollment is recorded as 97. These details describe the study timeline and planned population, but do not establish how many participants completed each assessment or contributed data to each outcome. Those counts are not reported in the registry record.
The study is classified as “other,” and its listed intervention is “no intervention.” The arm description names the Scottish swimming team. There is no described randomized allocation or like-for-like control comparison. Accordingly, the record supports describing this as a screening and assessment study, rather than as a trial comparing treatments.
The primary outcome is tidal nitric oxide, expressed in ppb, with a geometric mean and 95% confidence interval specified. Its timeframe is before pool entry and on exiting the pool. The record lists secondary outcomes of mannitol challenge, sport-based challenge, nasal nitric oxide, skin prick test, and mini nasal lavage. It records six outcome measures and zero analyses. Numerical outcome findings and details of the analysis procedures are not reported in the registry record.
The sponsor is Brian J Lipworth. The registry describes a screening objective, but does not report a detailed protocol, eligibility criteria, recruitment procedures, or the justification for enrollment. These omissions limit what can be inferred about how the study was carried out beyond the design elements explicitly recorded.
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: All members of the squad were offered the opportunity to take part.
Overall Study
| Stage | Scottish Swimming Team |
|---|---|
| STARTED | 97 |
| COMPLETED | 97 |
| NOT COMPLETED | 0 |
Analysis population for the primary outcome, as defined in the registry: Data from all participants was analysed
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.
| Characteristic | Unit | Scottish Swimming Team |
|---|---|---|
| Participants analysed | 97 | |
| Age, Categorical: <=18 years | Participants | 97 |
| Age, Categorical: Between 18 and 65 years | Participants | 0 |
| Age, Categorical: >=65 years | Participants | 0 |
| Age, Continuous | years | 15.2 (SD 0.25) |
| Sex: Female, Male: Female | Participants | 52 |
| Sex: Female, Male: Male | Participants | 45 |
| Region of Enrollment: United Kingdom | participants | 97 |
6. Primary Endpoint
The registry lists the primary outcome as Tidal Nitric Oxide, measured over This test will be performed prior to entering the pool, and on exiting the pool.
| Element | Registry entry |
|---|---|
| Result type | Geometric Mean |
| Measure of spread | 95% Confidence Interval |
| Unit | ppb |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint is tidal nitric oxide, measured in ppb. The registry specifies a geometric mean and a 95% confidence interval, with measurement planned before participants entered the pool and after they exited it. The record describes analysis of data from all participants. It does not report the geometric mean, the confidence interval limits, or the number of observations contributing to either assessment.
General: nitric oxide measured in exhaled air can be used as a physiological marker in respiratory assessment. A geometric mean is a summary on a multiplicative scale, commonly used when measurements are positive and their distribution is better represented after logarithmic transformation than on the original scale. This explanation describes the statistical meaning of the summary, not a finding about the distribution of measurements in this study; distributional information is not reported in the registry record.
General: a confidence interval expresses uncertainty around an estimated quantity under the assumptions of the analysis. Its width depends on factors such as variability and the amount of information available. A stated 95% confidence level does not itself reveal the estimated value or its precision in this study. Because the endpoint estimate and interval are not reported in the registry record, the size and precision of the observed tidal nitric oxide measurements cannot be assessed.
The before-pool and post-pool assessments give the endpoint a repeated-measurement context. However, the registry does not report how the measurements were compared, whether the analysis accounted for paired observations, or how missing measurements were handled. The endpoint specification therefore identifies what was measured and when, but not the numerical result or the full analysis method.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The record establishes that this completed pilot study enrolled 97 participants and focused on screening Scottish swimmers for asthma and rhinitis. It describes mannitol challenge and sport-based exercise challenge as screening approaches, alongside other assessments. It also identifies tidal nitric oxide as the primary outcome. These are descriptions of the study’s aim and outcome structure, not evidence of the screening results.
The primary outcome is defined as a geometric mean in ppb with a 95% confidence interval, assessed before pool entry and on exiting the pool. Neither the estimate nor the interval is reported in the registry record. As a result, the posted information does not permit an assessment of the observed tidal nitric oxide level, the size of any change between the stated assessments, or the precision of an estimate. No direction or magnitude of an outcome should be inferred from the endpoint description alone.
The registry names secondary outcomes covering mannitol challenge, sport-based challenge, nasal nitric oxide, skin prick testing, and mini nasal lavage. Their numerical findings are not reported in the registry record. The stated study purpose refers to identifying prevalence, but the record does not provide prevalence estimates or counts of participants identified through screening. It is therefore not possible to describe how often asthma or rhinitis was identified, or to compare the screening approaches on the basis of the posted results.
The registry records zero analyses. This means that no analysis results are reported in the record; it does not establish that no analyses were conducted outside the record. The analysis populations, procedures, and any adjusted estimates are not reported in the registry record. Although the primary outcome description says data from all participants was analysed, the number contributing data and the definition of that analysis population are not given.
General: estimates and confidence intervals are needed to distinguish an observed pattern from the uncertainty around it. Without the actual estimate, interval, and relevant participant counts, statistical precision cannot be judged. No statistical significance claim can be made from the outcome definitions alone. There are no reported p-values or comparative estimates in the registry record.
The adverse-event record lists zero participants at risk and zero affected for both serious and other events in the Scottish Swimming Team group. These entries do not provide an interpretable safety rate because the record shows no participants at risk for those summaries. Deaths are recorded as null, rather than as a numerical count. The registry information therefore should not be read as establishing the absence of adverse events.
Overall, the record supports a description of the study question, population, assessments, and planned primary outcome. It does not support conclusions about diagnostic yield, prevalence, relationships between challenge tests, changes in nitric oxide, or the uncertainty of any such findings.
9. Statistical Methods Explained
General: statistical methods connect a study question to an estimate and describe the uncertainty around that estimate. A method can be evaluated only when its inputs, assumptions, and output are known. In this registry record, the primary outcome summary type and confidence level are specified, but the outcome estimate and analysis details are not reported. The explanations below clarify the statistical concepts relevant to the recorded design without attributing unreported methods to the study.
What does a geometric mean describe?
General: the arithmetic mean adds measured values and divides by the number of observations. The geometric mean instead summarizes positive values on a multiplicative scale. It is commonly calculated by transforming values to logarithms, averaging those transformed values, and returning the average to the original scale. This can be suitable when data are skewed or when relative rather than absolute variation is meaningful. The registry does not report the distribution of tidal nitric oxide measurements or the rationale for choosing a geometric mean, so the suitability of that summary for the observed data cannot be assessed.
A geometric mean is not interchangeable with an arithmetic mean. Its interpretation depends on the measurement scale and the data structure. The record gives the unit as ppb and specifies a geometric mean, but does not provide the estimate, the underlying observations, or a description of any transformation used in analysis.
How should a confidence interval be understood?
General: a confidence interval is an interval estimate that represents sampling uncertainty under a statistical procedure and its assumptions. A 95% confidence interval is associated with a procedure designed to cover the target quantity in 95% of repeated applications under those assumptions. It is not a range containing 95% of individual participants’ measurements, and it is not by itself a probability statement about a fixed result after the interval has been calculated.
The registry specifies a 95% confidence interval for the primary endpoint, but neither endpoint values nor interval limits are reported in the registry record. Consequently, the interval cannot be used to judge precision, and it cannot support a comparison of the before-pool and post-pool assessments. The method used to calculate the interval is also not reported.
What does the repeated assessment imply?
General: measurements taken from the same participant at different times are usually statistically related. An analysis that compares within-participant measurements can account for that pairing, whereas an analysis treating all measurements as independent may fail to represent the data structure. The record gives a before-pool and an exiting-pool timeframe, but does not describe whether the analysis used paired differences, a repeated-measures model, or another approach. No particular analysis should be assumed.
General: the interpretation of a pre- and post-assessment comparison also depends on consistency of measurement procedures and the completeness of observations at each assessment. The registry does not report timing details beyond the stated pool-related timeframe, measurement procedures, or the number of paired observations. It is therefore not possible to assess these factors from the registry record.
How do screening assessments relate statistically?
The registry summary describes both mannitol challenge and sport-based exercise challenge as screening methods, and lists outcomes relating to those challenges. General: when two screening methods are assessed in the same population, a comparison may examine agreement, sensitivity, specificity, or other measures, depending on the study question and reference standard. Those measures require defined classifications and participant-level results. The registry does not report a reference standard, diagnostic classification rules, cross-tabulations, or estimates of screening performance. No agreement or accuracy measure can therefore be inferred.
The study aim refers to prevalence. General: a prevalence estimate requires a defined case definition and a clearly specified population and assessment period. Its precision depends in part on the number of participants assessed and the observed number meeting that definition. The record does not report case counts, a prevalence estimate, or the details needed to establish how cases were defined. Enrollment alone cannot be used to calculate prevalence.
What can be said about planning assumptions?
The registry record describes a planning illustration based on an observed effect, using a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. It describes the effect to detect as a stated fraction of the observed effect. The illustration is not the trial’s own design justification, and the record does not report a sample-size justification for the study. No numerical planning estimates are reported in the record.
General: a planning calculation estimates the sample size needed under specified assumptions about effect size, variability, allocation, and the chosen error rate. Changing those assumptions changes the planning result. A planning estimate based on an observed effect is a hypothetical illustration; it is not observed power and does not establish that a study was adequately powered. The record’s stated assumptions should not be confused with a confirmed allocation scheme, especially because the study is not described as a randomized comparison and its arm is the Scottish swimming team.
Why does over-dispersion matter in general?
General: over-dispersion occurs when the variability in observed data is greater than a statistical model assumes. If it is ignored, standard errors may be understated and confidence intervals may be too narrow. Appropriate modeling depends on the outcome type and data structure. The registry does not report an over-dispersion assessment or a model for the outcomes, so this issue cannot be evaluated as a feature of this study.
More broadly, the registry does not report an analysis plan, model specifications, covariate adjustments, handling of repeated measures, or diagnostic checks. These are not details that can be reconstructed from the endpoint title or the stated summary measure. The statistical description should therefore remain limited to what the record explicitly identifies: the primary outcome, its unit and summary type, its stated confidence level and timeframe, and the named secondary outcomes.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists a primary outcome and several secondary outcomes, including challenge assessments, nasal nitric oxide, skin prick testing, and mini nasal lavage. It records six outcome measures and zero analyses, but does not report numerical outcome findings. The statistical analysis plan, including whether any multiplicity adjustment was planned, is not reported in the registry record.
General: multiplicity arises when several outcomes, time points, or comparisons are examined. Without an approach to account for multiple testing, the chance of at least one apparently notable result can increase. Possible approaches depend on whether outcomes are confirmatory or exploratory and on the study’s objectives. No adjustment method or hierarchy of secondary outcomes can be assumed for this study. As no analysis results are reported, the effect of multiplicity on any findings cannot be assessed.
The primary outcome description states that data from all participants was analysed. The registry does not give the number contributing to each assessment, the number with missing values, reasons for missingness, or methods for handling incomplete records. It also does not describe exclusions from analyses or how participants with only one of the stated pool-related measurements were treated.
General: missing data can affect an estimate when the likelihood of missingness is related to participant characteristics or outcome values. Complete-case analysis, imputation, and model-based methods make different assumptions; their appropriateness depends on the pattern and causes of missingness. The registry does not report which, if any, such methods were used.
The analysis population is not defined beyond the statement that data from all participants was analysed for the primary endpoint. The record does not describe an intention-to-treat population, a per-protocol population, or outcome-specific analysis sets. It is therefore not possible to determine the exact denominator for reported analyses, and no denominator-based result can be reconstructed from the record.
11. What the Result Does, and Does Not, Mean
The registry record describes a completed pilot screening study among Scottish swimmers, with enrollment of 97 and assessments intended to identify asthma and rhinitis. It records mannitol challenge and sport-based exercise challenge in the study summary, and identifies tidal nitric oxide as the primary endpoint. These details clarify the study’s purpose and measurement plan, but do not establish the results of screening.
The measured tidal nitric oxide geometric mean and 95% confidence interval are not reported in the registry record. Nor are numerical findings for the listed secondary outcomes or prevalence estimates for asthma and rhinitis. As a result, the posted information cannot establish how many participants met any case definition, whether the two challenges gave similar classifications, or whether nitric oxide measurements differed between the stated assessments.
General: a pilot study can help characterize procedures and generate estimates for later research, but a pilot designation alone does not show that estimates are precise or representative. Interpretation depends on recruitment, completion, measurement quality, outcome definitions, and analysis methods. The registry record does not report enough information on these features to judge their influence on the study findings.
The record does not establish a treatment effect. The listed intervention is no intervention, and the study is not a randomized comparison. It also does not provide a like-for-like control group. Therefore, the findings cannot be interpreted as a comparison of treatment benefits or harms. The statistical description should remain focused on screening and measurement rather than causal treatment claims.
The adverse-event entries show zero participants at risk and zero affected in the recorded group, while the death count is null. Those entries cannot be treated as evidence that no events occurred, because a zero at-risk denominator does not provide a meaningful rate. The registry does not report further adverse-event details.
In practical statistical terms, the record identifies what the investigators intended to measure, but not the estimates needed to judge magnitude, precision, or screening performance. Conclusions about prevalence, diagnostic accuracy, associations, or safety are not supported by the registry information alone.
12. Why This Trial Matters Statistically
This study is statistically notable as a screening project that brings together challenge-based assessments and respiratory measurements in a defined athletic population. Its stated objective concerns exercise-induced asthma and rhinitis in Scottish swimmers, while the primary endpoint is tidal nitric oxide measured around pool entry and exit. The combination makes the study’s measurement question distinct from a conventional treatment comparison.
General: screening studies raise methodological questions that differ from those in trials designed to estimate treatment effects. The definition of a positive screen, the reference standard used to classify cases, and the agreement between assessment methods are central to interpreting screening performance. The registry record names the tests but does not report a reference standard, diagnostic rules, or estimates of accuracy. That absence illustrates why listing an assessment is not equivalent to reporting its performance.
The endpoint also highlights the importance of matching a statistical summary to the data. A geometric mean and confidence interval are specified, but without the estimate, interval, distribution, and analysis details, readers cannot assess the level or precision of the measurements. General: reporting both an estimate and its uncertainty is essential to distinguish a potentially informative pattern from one that remains imprecise.
The record identifies a completed pilot study with enrollment of 97, but its analysis reporting is limited: zero analyses are recorded. This makes transparent registry reporting especially important. A complete account of outcome counts, denominators, missingness, and analysis methods would allow readers to understand how the screening question was evaluated. These details are not reported in the registry record.
The study matters statistically as an example of how a clear clinical objective can coexist with limited posted numerical evidence. The record establishes the intended population, assessments, and primary outcome, while leaving the central estimates unavailable. That distinction helps prevent readers from treating a study’s purpose or completion status as a reported result.
13. 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.
A major limitation of the available record is that it does not report numerical results for the primary or secondary outcomes. The tidal nitric oxide estimate and its 95% confidence interval are absent, as are results for mannitol challenge, sport-based challenge, nasal nitric oxide, skin prick test, and mini nasal lavage. The record therefore does not permit assessment of the study’s central screening findings.
Although the study objective refers to identifying prevalence, no prevalence estimate or case count is reported. The registry also does not report diagnostic criteria, a reference standard, or how a positive screening result was defined. Without those details, screening yield and diagnostic performance cannot be characterized.
The design information is limited. The arm is described as the Scottish swimming team, and the listed intervention is no intervention. The study is not a randomized comparison, and the arms are not described as a like-for-like control comparison. The record does not explain allocation beyond stating that it is not stated, nor does it provide further detail on recruitment, eligibility, or participant characteristics.
For the primary outcome, the registry specifies a geometric mean, a 95% confidence interval, and a before-pool and exiting-pool timeframe. It does not report the analysis method, the number of participants contributing at either assessment, the handling of paired observations, or the treatment of missing values. The statement that data from all participants was analysed does not define outcome-specific denominators or analysis populations.
The registry records zero analyses and does not report a statistical analysis plan, multiplicity procedure, or sample-size justification. Its planning illustration is not the trial’s own design justification and is not observed power. The adverse-event entries also list zero participants at risk, limiting their interpretability. These gaps restrict the conclusions that can be drawn from the registry record, rather than establishing that the study itself lacked procedures or analyses not recorded there.
14. Related Tutorials
15. Related Statistical Calculators
16. Sources
- ClinicalTrials.gov: Screening Scottish Swimmers for Asthma and Rhinitis — NCT00831428.
- Registry record last updated 2019-04-24; status last verified 2019-04.
- Results first posted 2011-09-23.
- 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.
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17. Record Summary
NCT00831428, “Screening Scottish Swimmers for Asthma and Rhinitis,” is recorded as a completed pilot study sponsored by Brian J Lipworth. The registry lists a start date of 2009-02, primary completion of 2009-05, and enrollment of 97. Its stated aim was to screen Scottish swimming teams for asthma and rhinitis using mannitol challenge and sport-based exercise challenge.
The primary outcome is tidal nitric oxide in ppb, summarized as a geometric mean with a 95% confidence interval, with assessments planned before pool entry and on exiting the pool. Secondary outcomes include mannitol challenge, sport-based challenge, nasal nitric oxide, skin prick test, and mini nasal lavage. The arm is the Scottish swimming team, and the listed intervention is no intervention.
The registry records six outcome measures and zero analyses. Numerical outcome findings, prevalence estimates, analysis details, and the primary endpoint confidence interval are not reported in the registry record. The recorded adverse-event group has zero participants at risk and zero affected, with deaths listed as null.