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 Dose-response of Albuterol in Asthmatics (NCT00940927), a na phase 4 study. The primary outcome is Effective Dose 50% (ED50).
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT00940927 |
| Phase | Phase 4 |
| Condition | Asthma |
| Allocation | Not applicable (single group) |
| Design model | Single Group |
| Masking | None (open label) |
| Enrollment | 81 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Nemours Children's Clinic |
| Results posted | Yes |
2. Clinical Question
Population
Children and adults with asthma were the population described in the study summary. The registry record lists 81 participants as enrolled. Further eligibility details, including age ranges and criteria for asthma severity, are not reported in the registry record.
Intervention
The intervention was albuterol, administered in increasing doses. The study summary describes the purpose as determining lung function response after those dose increases. Dose amounts and administration details are not reported in the registry record.
Comparator
The design is listed as single group, with allocation recorded as NA and masking as none. No control or comparator group is identified. The registry record therefore does not describe a randomized, like-for-like comparison between treatment groups.
Primary question
The primary outcome was Effective Dose 50% (ED50), measured in ug. It is defined as the cumulative albuterol dose required to bring about 50% of albuterol’s maximum effect, assessed 15 minutes after each dose. In plain terms, the study’s stated question was what cumulative dose corresponded to half of the maximum effect in the lung-function response being assessed. The registry record does not report an ED50 estimate or explain how the maximum effect was determined.
3. Trial Design
This is a completed phase 4 study of albuterol in people with asthma. Its title is “Dose-response of Albuterol in Asthmatics,” and its official title is “Exclusion of Asthmatics From Clinical Trials Due to the 15 Percent Rule.” The registry record lists Nemours Children's Clinic as the sponsor, asthma as the condition, and albuterol as the drug intervention. The study dates are recorded as 1993-07 for start and 1994-10 for primary completion.
The design is classified as single group. Allocation is recorded as NA, and masking is listed as none. The record therefore does not describe random assignment or masking, nor does it identify a concurrent control group. Its stated objective was to assess lung function response after increasing albuterol doses in children and adults with asthma. The primary outcome was ED50, a cumulative dose measure expressed in ug, with assessment specified as 15 minutes after each dose.
The record lists 81 participants enrolled. That is an enrollment count; it should not be treated as the number with a reported primary outcome, because outcome availability and analysis populations are not reported in the registry record. The record lists two outcome measures, but details of the other outcome are not reported in the registry record. It also lists no analysis records. Details of dose schedules, eligibility criteria, follow-up beyond the stated outcome timeframe, and the protocol’s planned statistical analysis are not reported in the registry record. The study’s completed status indicates its recorded status, but does not by itself establish that results were analyzed or posted.
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: Participants had to withhold inhaled short-acting beta2 agonist or inhaled anticholinergic drugs for 8 h, oral antihistamines for 5 days, theophylline for 24 h, and cromolyn, nedocromil, and inhaled corticosteroids for 2 h prior to the study.
Overall Study
| Stage | Albuterol |
|---|---|
| STARTED | 81 |
| COMPLETED | 81 |
| NOT COMPLETED | 0 |
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 | Albuterol |
|---|---|---|
| Participants analysed | 81 | |
| Age, Categorical: <=18 years | Participants | 31 |
| Age, Categorical: Between 18 and 65 years | Participants | 48 |
| Age, Categorical: >=65 years | Participants | 2 |
| Age, Continuous | years | 30.2 (SD 17.4) |
| Sex: Female, Male: Female | Participants | 45 |
| Sex: Female, Male: Male | Participants | 36 |
| Region of Enrollment: United States | participants | 81 |
6. Primary Endpoint
The registry lists the primary outcome as Effective Dose 50% (ED50), measured over 15 minutes after each dose.
| Element | Registry entry |
|---|---|
| Result type | Number |
| Measure of spread | not applicable |
| Unit | ug |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint is Effective Dose 50% (ED50), measured in ug. The record defines it as the cumulative dose of albuterol required to bring about 50% of albuterol’s maximum effect. The stated timeframe is 15 minutes after each dose. Unlike an outcome that records only whether a response occurred, an ED50 expresses the amount of drug associated with a defined level of response, making it a way to characterize dose-response.
In general, dose-response measures can describe how much exposure is associated with a specified response level. An ED50 can be useful for characterizing the dose needed to reach a response threshold, particularly when a study administers increasing doses. The interpretation depends on how the response and maximum effect are measured, and on whether the dose-response data support estimating that threshold. Those operational details are not reported in the registry record.
The record names ED50 as the primary outcome but does not give a value, dispersion measure, confidence interval, or analysis result. It therefore does not establish the estimated dose or the precision of that estimate. The outcome definition alone describes what the study intended to measure; it is not evidence of the observed ED50.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record describes a single-group, unmasked study of increasing albuterol doses in children and adults with asthma. It lists 81 participants enrolled and names ED50 as the primary outcome. However, it does not report the ED50 value, a measure of its uncertainty, or an inferential analysis. Consequently, the posted record does not allow readers to assess the magnitude or precision of the primary endpoint estimate.
The ED50 definition gives the target quantity: the cumulative dose required to bring about 50% of maximum albuterol effect, measured in ug, with assessment 15 minutes after each dose. This definition helps identify what an estimate would mean, but it cannot substitute for the estimate itself. Without the outcome value or the underlying dose-response information, the record does not show where the estimated threshold lies or how stable it may be.
The single-group design also defines the scope of interpretation. There is no control group listed, and allocation is NA. The record therefore does not support a treatment-versus-control contrast. Even if an ED50 result were available, it would describe the dose-response assessment in the studied group; it would not, by itself, provide a randomized comparison with another treatment or establish how responses differ from a comparator group.
The registry lists no analysis records. The primary outcome’s numeric result, statistical method, uncertainty estimate, and analysis population are not reported in the registry record. The second outcome is not described in the record details available for this study. These omissions mean that no claim about statistical significance, precision, or consistency of the outcome can be drawn from the registry information.
The adverse-event counts should be read separately from the efficacy endpoint. The albuterol group has zero serious adverse events and zero other adverse events recorded, with 81 at risk for each category. Deaths are not reported in the registry record. These counts are registry entries, not a substitute for information about how events were collected, their timing, or completeness of reporting.
Overall, the record establishes the study’s stated question, design classification, enrollment, and primary outcome definition. It does not provide the outcome results needed to quantify the dose-response finding. The completed status and the existence of a defined endpoint should not be mistaken for a reported estimate or an analysis of that endpoint.
9. Statistical Methods Explained
ED50 is a dose-response summary. In general, a dose-response analysis relates different administered doses to the response measured at those doses. An ED50 targets the dose associated with half of the maximum effect, according to the record’s definition. The study summary says that lung function response was assessed after increasing albuterol doses, while the primary outcome specifies a cumulative dose and a measurement timeframe of 15 minutes after each dose.
To estimate such a quantity, an analysis needs response information across doses and a definition of the response scale and maximum effect. In general, the estimate may depend on the shape of the dose-response relationship and on how much information is available around the target response level. The registry record does not describe the response scale, the method for determining maximum effect, the dose schedule, or the estimation procedure. It also does not report the ED50 estimate. These gaps prevent assessment of how the endpoint was operationalized or how reliably it was estimated.
A confidence interval is a general statistical way to express uncertainty around an estimate. It indicates a range of values compatible with the data under the stated analysis method; it does not show that every value in that range is equally plausible, and it does not replace the estimate itself. No confidence interval or other uncertainty measure for ED50 is reported in the registry record. Without that information, the precision of any primary outcome estimate cannot be evaluated from the record.
Hypothesis tests and confidence intervals answer related but different questions. A test evaluates data against a specified null hypothesis under a model, while an interval emphasizes the range of effect sizes consistent with the data under that model. The registry record contains no analysis records and reports no p-value, test statistic, or interval for the primary endpoint. The statistical test, if any, and its assumptions are not reported in the registry record. It would therefore be inappropriate to infer statistical significance or to reconstruct an analysis from the outcome definition alone.
The design is listed as single group, with allocation NA and masking none. In general, a single-group dose-response study can characterize responses across doses in the participants studied, but it does not supply a concurrent untreated or alternative-treatment group for a randomized contrast. The registry record does not describe a control condition. Any interpretation should remain focused on the stated dose-response question rather than a comparative treatment effect.
The record includes a sample-size planning description with two-sided significance level 0.05, equal allocation between two arms, and a normal approximation. It says the effect to detect is a stated fraction of the observed effect. These are planning assumptions, not a description of the registered single-group study’s allocation. The planning description also says that sample sizes are illustrations computed from the observed effect, rather than the trial’s own design. The numerical planning outputs and the observed effect value are not reported in the registry record. Such planning illustrations should not be read as observed power or as evidence that the trial was designed or analyzed according to those assumptions.
In general, power is a design-stage probability tied to a specified effect, variability, analysis, and significance level. It is not a measure of the probability that a finding is true, and an observed result should not be described as having a particular “observed power.” A planning calculation can help illustrate how assumed effect size and design choices influence required sample size. Its relevance depends on whether those assumptions correspond to the question and design of interest. Here, the listed planning assumptions describe a hypothetical equal-allocation, two-arm comparison, while the registry’s study design is single group. They should therefore be kept distinct.
For dose-response estimates, uncertainty can also reflect variation in participants’ responses and the information available at each dose. General statistical methods may model the relationship between dose and response, but the registry record does not name a model or provide dose-level observations. It is not possible to determine whether the analysis accounted for repeated measurements, how missing measurements were handled, or whether model assumptions were checked. Those methods are not reported in the registry record.
The outcome is listed as a number with unit ug, and no dispersion value is reported. The endpoint label alone does not identify an appropriate probability model or establish that the endpoint should be analyzed as a count. Statistical interpretation depends on the form of the actual measurements and the analysis plan, neither of which is described in the registry record. For the same reason, no distributional assumption or standard error should be inferred.
10. Multiplicity, Missing Data and Analysis Populations
The registry record lists two outcome measures and identifies ED50 as the primary outcome. Details of the other outcome and any analysis of it are not reported in the registry record. The record does not describe whether outcomes were tested in a prespecified hierarchy, whether any adjustment for multiple testing was planned, or how multiple dose-related comparisons would be handled. A multiplicity strategy is not reported in the registry record.
In general, multiplicity arises when several outcomes, contrasts, or analyses are examined. Conducting multiple tests can increase the chance of at least one apparently unusual result when all null hypotheses are true. Adjustment strategies and prespecified priorities can help make interpretation more transparent. Because the registry record does not report the analysis plan or results, it is not possible to assess whether multiplicity was relevant to the analyses actually conducted or how it was addressed.
Missing-data methods and outcome availability are also not reported in the registry record. The record lists 81 participants enrolled, but does not state how many contributed to the primary endpoint analysis, whether any dose-response measurements were incomplete, or how incomplete observations were handled. Enrollment should not be treated as proof that every participant had a usable ED50 measurement.
The record does not define analysis populations, such as which participants were included in the primary endpoint calculation. It also does not describe exclusions after enrollment or any sensitivity analyses. These details matter because an estimate can depend on which observations are included and how missing measurements are treated. No conclusion about completeness or analysis-population differences can be drawn from the registry record.
11. Safety Results
The registry reports serious adverse events as affected participants divided by participants at risk.
| Arm | Participants with serious adverse events | Participants at risk | Percentage |
|---|---|---|---|
| Albuterol | 0 | 81 | 0.0% |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 0% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Albuterol | 0 of 81 |
For the albuterol group, the registry lists 81 participants at risk for serious adverse events and zero with a serious adverse event. It also lists 81 at risk for other adverse events and zero with an event in that category. These are separate registry categories and should be read as recorded counts, not as proof that no event occurred outside the record’s collection or reporting process. No serious adverse-event terms are listed.
Deaths are not reported in the registry record. A missing death count is not equivalent to a reported zero. The record does not describe event definitions, monitoring procedures, follow-up duration for safety, or the completeness of event reporting. It also does not provide further context for interpreting the at-risk counts.
In general, a zero count means that no events in that category were recorded for the specified group in the record. It does not establish that the true risk is zero, particularly when event ascertainment and follow-up details are unavailable. The registry counts should therefore be described narrowly, without converting them into rates or making comparative safety claims.
12. What the Result Does, and Does Not, Mean
The record’s primary contribution is a clear statement of the dose-response question and endpoint: ED50, defined as the cumulative albuterol dose required to produce 50% of maximum effect, with assessment 15 minutes after each dose. It also records a single-group, unmasked design, 81 enrolled participants, and a completed status. These registry entries describe the study’s intended focus and its registry classification.
The registry record does not report the primary outcome result or any analysis records. It therefore does not show an estimated ED50, its precision, or how the response varied across doses. Readers cannot use the record to quantify the observed lung function response or determine whether an inferential analysis supported a particular conclusion. The endpoint definition is not itself a result.
The design also limits what the question can answer. The record lists no comparator and no random allocation. It does not provide a randomized comparison between albuterol and another intervention or a control condition. Thus, the record cannot establish a comparative treatment effect. The study’s title refers to the 15 Percent Rule, but the rule’s definition and its relationship to the study procedures are not reported in the registry record.
The adverse-event entries show zero recorded serious and other adverse events in the listed categories, alongside the recorded at-risk counts. They do not supply a full account of safety ascertainment, and deaths are not reported in the registry record. These entries should not be broadened into a claim that the intervention has no risk.
In general, a result’s meaning depends on the estimate, uncertainty, design, and analysis population. Here, the available registry information supports describing the intended measurement and study structure, but not the magnitude, precision, or comparative meaning of the primary outcome. The completed designation does not fill in those missing results.
13. Why This Trial Matters Statistically
This study is statistically interesting because its stated question concerns a dose-response relationship rather than a simple comparison between treatment groups. ED50 translates a response curve into a dose associated with a defined response level. That kind of summary can be useful for describing how dose and response relate, provided the response scale, maximum effect, dose schedule, and estimation method are clearly specified.
The registry classification makes an important interpretive distinction visible: this is a single-group study, with allocation listed as NA and masking as none. Statistical questions about dose-response within a group differ from questions about comparative effectiveness between randomized groups. A study without a listed comparator cannot directly estimate a randomized between-group contrast, regardless of how its endpoint is labeled.
The record also illustrates why an outcome definition and a result are not interchangeable. ED50 is precisely named and has a stated unit and timeframe, but its numeric estimate and uncertainty are not reported. A well-defined endpoint helps readers understand the intended measurement; it cannot show what the study found. The absence of analysis records further limits interpretation.
Finally, the sample-size planning assumptions describe an equal-allocation, two-arm illustration, whereas the registered design is single group. Keeping hypothetical planning assumptions separate from the actual design prevents sample-size illustrations from being mistaken for features of the study or evidence of observed power. The distinction is broadly important whenever planning calculations and a completed study’s analysis are presented together.
14. Limitations
- The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
- Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.
The registry record does not provide the primary ED50 estimate, its uncertainty, or an inferential analysis. It also does not provide dose-level response data, the response scale, or the method used to determine maximum effect. As a result, the central dose-response finding cannot be independently interpreted from the registry information.
The study is listed as single group, with allocation NA and masking none. No comparator is identified, so the record does not support a randomized comparative interpretation. The title’s reference to the 15 Percent Rule does not explain what the rule means or how it was applied; that information is not reported in the registry record.
Eligibility details, participant age ranges, dose amounts, administration procedures, and relevant follow-up details are not reported in the registry record. The record lists 81 enrolled, but does not identify the analysis population or state whether all enrolled participants contributed to the primary outcome. The missing-data approach is not reported in the registry record.
The record lists two outcome measures, but the other outcome’s details and any multiplicity strategy are not reported. The adverse-event listing records zero serious and zero other events in the respective categories, but does not describe event ascertainment or follow-up; deaths are not reported in the registry record. These limitations leave both efficacy interpretation and safety context dependent on information beyond the registry entries described.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Dose-response of Albuterol in Asthmatics — NCT00940927.
- Registry record last updated 2015-05-05; status last verified 2015-04.
- Results first posted 2009-07-17.
- 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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18. Record Summary
NCT00940927 is a completed phase 4 study sponsored by Nemours Children's Clinic. The study began in 1993-07 and reached primary completion in 1994-10. Its condition is asthma, and the intervention is albuterol. The stated purpose was to assess lung function response after increasing doses in children and adults with asthma.
The design is listed as single group, with allocation NA and masking none. The record lists 81 enrolled participants and two outcome measures. The primary outcome is ED50, measured in ug and defined as the cumulative dose required for 50% of maximum albuterol effect, assessed 15 minutes after each dose. No analysis records or primary outcome result are reported. Serious and other adverse-event counts are recorded as zero in the listed albuterol group; deaths are not reported in the registry record.