This page separates information reported in the ClinicalTrials.gov record from statistical interpretation. The registry data indicate that results have been posted, but no formal statistical analyses, effect estimates, confidence intervals, or p-values are included in the ClinicalTrials.gov record.
1. Trial at a Glance
MIST was a completed randomized phase 3 trial in asthma evaluating budesonide strategies in wheezing toddlers. The ClinicalTrials.gov record describes a parallel-group, quadruple-masked design with 278 enrolled participants and one registered primary endpoint: the rate of exacerbations requiring systemic corticosteroids during the 12-month follow-up period.
| Feature | MIST |
|---|---|
| Trial name | MIST |
| Brief title | CARE Network Maintenance Versus Intermittent Inhaled Steroids in Wheezing Toddlers (MIST) |
| Condition | Asthma |
| Phase | Phase 3 |
| Status | Completed |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | Quadruple |
| Primary purpose | Treatment |
| Enrollment | 278 |
| Arms | 2 |
| Lead sponsor | Milton S. Hershey Medical Center |
| Sponsor type | OTHER |
| Start | 2008-08 |
| Primary completion | 2010-07 |
| Results posted | Yes |
| Outcome measures posted | 11 |
2. Clinical Question
The registered trial question concerns maintenance versus intermittent inhaled steroid treatment in wheezing toddlers with asthma. The ClinicalTrials.gov record identifies budesonide and placebo budesonide as the two drug interventions and identify the trial as randomized, parallel, quadruple-masked, and intended for treatment evaluation.
Population
Wheezing toddlers with asthma, as described by the trial's brief title and condition.
Intervention
Budesonide.
Comparator
Placebo budesonide.
Primary question
How does the registered rate of exacerbations requiring systemic corticosteroids compare under the trial's treatment strategies during the 12-month follow-up period?
3. Trial Design
Budesonide
- Drug intervention: budesonide
- Part of the randomized parallel-group comparison
Placebo Budesonide
- Drug intervention: placebo budesonide
- Part of the randomized parallel-group comparison
The ClinicalTrials.gov record also identify the safety groups as Daily Budesonide and Intermittent Budesonide. Because the ClinicalTrials.gov record does not explicitly provide a complete arm-level treatment schedule or a numerical mapping between every intervention field and every safety label, this page keeps those labels distinct rather than adding treatment details that are not present in the source data.
4. Trial Timeline
Trial start
The registry lists August 2008 as the study start.
Primary completion
The registry lists July 2010 as the primary completion date.
Registry status
The trial is listed as completed, with results posted and 11 outcome measures posted.
5. Primary Endpoint
| Endpoint | Registry definition | Time frame | Endpoint type |
|---|---|---|---|
| Rate of Exacerbations Requiring Systemic Corticosteroids | The rate of exacerbations was calculated as the number of exacerbations requiring prednisone per years of follow-up. | Measured during the 12-month follow-up period | Count / rate |
This endpoint is fundamentally different from a binary outcome such as whether a participant experienced at least one exacerbation. The registered measure is a rate: it uses the number of exacerbations together with the amount of follow-up time.
The denominator is important. Two groups could have similar numbers of events but different rates if their accumulated follow-up differs.
6. Results
The ClinicalTrials.gov record indicates that results have been posted and that 11 outcome measures are available. However, no formal statistical analyses were posted. Therefore, the available trial data do not provide a formal treatment-effect estimate, confidence interval, or p-value for the registered primary endpoint.
| Primary endpoint | Results status in the ClinicalTrials.gov record | Formal statistical result reported? |
|---|---|---|
| Rate of Exacerbations Requiring Systemic Corticosteroids | Results posted | No statistical analysis entry, estimate, confidence interval, or p-value reported |
What a formal comparison would normally report
For a randomized trial in which the primary endpoint is the number of events per unit of follow-up, an appropriate analysis would generally compare event rates rather than simply comparing the percentages of participants with an event. A count model can incorporate each participant's exposure time through an offset, producing a treatment-effect measure such as a rate ratio.
Here, Yi represents the event count and the follow-up-time term acts as an exposure offset. The exponentiated treatment coefficient, eβ₁, can be interpreted as a rate ratio under the specified model.
Poisson regression is one standard starting point for count-rate data. If the event counts are more variable than the Poisson model permits, a negative-binomial model can be considered. These are general statistical approaches for this endpoint type, not methods reported as having been used in the registry-reported MIST statistical-analysis field.
The primary endpoint is designed to capture the frequency of clinically important exacerbations over time, rather than merely whether an individual experienced one. That makes the amount of follow-up part of the estimand.
Without the actual event counts, exposure times, estimated rate ratio or rate difference, confidence interval, and p-value, there is no defensible numerical treatment effect to interpret. The absence of those values in the ClinicalTrials.gov record should not be replaced with an estimate reconstructed from unrelated sources.
A confidence interval, when available, would describe the precision of the estimated treatment effect; it would not describe the range of exacerbation counts that individual children could experience. A p-value would address evidence against a specified null hypothesis; it would not measure the size or clinical importance of the treatment effect.
7. Safety Results
The ClinicalTrials.gov record provides serious adverse events by arm. These are reported as affected participants divided by participants at risk.
| Safety group | Serious adverse events | Interpretation of registry-reported measure |
|---|---|---|
| Daily Budesonide | 7/139 | 7 affected participants among 139 at risk |
| Intermittent Budesonide | 10/139 | 10 affected participants among 139 at risk |
The denominators are equal in the ClinicalTrials.gov record, which makes the affected-participant counts directly comparable descriptively. However, the ClinicalTrials.gov record does not include a statistical analysis of serious adverse events, so no formal confidence interval or p-value should be assigned to the difference.
8. Statistical Methodology
Why the endpoint is a count/rate outcome
The registry classifies the primary endpoint as Count / rate. The numerator is the number of exacerbations requiring prednisone, while the denominator is years of follow-up. This structure preserves information about repeated events and follow-up duration.
Rate versus proportion
A proportion asks how many participants experienced an event at least once. A rate asks how many events occurred relative to accumulated observation time. If one participant experiences multiple qualifying exacerbations, a rate-based endpoint can retain that repeated-event information rather than collapsing everything into a single yes/no indicator.
Poisson-type modeling
A Poisson model is a conventional framework for event counts when the mean and variance assumptions are reasonable. Follow-up time can be included as an offset so that the model compares rates rather than raw counts.
A rate ratio below 1 would indicate a lower estimated event rate in the numerator group relative to the denominator group; a rate ratio above 1 would indicate a higher estimated event rate.
Overdispersion and repeated events
Clinical event counts can exhibit greater variability than a simple Poisson model assumes. When that occurs, negative-binomial methods are often considered. Repeated exacerbations also mean that the statistical model should be chosen with the event-generation process in mind rather than treating every count as if it were an independent binary observation.
Exposure time
The registry definition explicitly uses years of follow-up. This makes exposure time a central component of the endpoint. A rate model can account for unequal observation periods through an offset, whereas a simple comparison of raw event counts would not.
Randomization and causal comparison
Randomization is a key design feature because treatment assignment is randomized rather than selected by investigators or participants. This supports a causal comparison of treatment strategies when the randomized groups are analyzed according to the prespecified trial framework. The ClinicalTrials.gov record, however, do not provide the statistical-analysis details needed to determine the exact analysis population or estimator used for the primary result.
9. Statistical Methods Explained
Why is a rate used instead of simply counting children with exacerbations?
The registered endpoint counts exacerbations requiring prednisone and divides by years of follow-up. This allows the analysis to represent the frequency of events over time. A participant with more than one qualifying exacerbation can contribute multiple events to the rate.
What does "per years of follow-up" accomplish?
It converts the raw event count into an exposure-adjusted measure. If participants contribute different amounts of observation time, the denominator helps distinguish a group with many events because it was observed longer from a group with a genuinely higher event frequency.
Why might a Poisson model be considered?
Poisson regression is designed for count outcomes and can incorporate follow-up time as an offset. For this endpoint, the treatment coefficient can therefore represent a relative difference in exacerbation rates. The registry-reported MIST data do not identify Poisson regression as the actual registry analysis, so this is an educational explanation of a typical approach.
Why might negative-binomial regression be useful?
Poisson models impose a relatively restrictive relationship between the mean and variance of the count distribution. If some children have substantially more exacerbations than others, the observed variability may exceed that assumption. Negative-binomial models provide an additional dispersion parameter and are often used for overdispersed count data.
Why isn't a p-value enough to understand this endpoint?
A p-value addresses the compatibility of the observed data with a specified null hypothesis. It does not tell the reader how large the treatment difference is. For a rate endpoint, the effect estimate—such as a rate ratio or rate difference—together with its confidence interval provides the information needed to understand magnitude and precision.
What would a rate ratio below 1 mean?
If the treatment-group rate ratio were 0.70, for example, it would mean that the estimated exacerbation rate in the treatment group was 70% of the comparator rate under the specified model. That would correspond to a 30% lower estimated rate, but it would not mean that 30% of children avoided exacerbations or that every child experienced exactly the same reduction.
10. Planned Analysis
Because the ClinicalTrials.gov record contains no formal statistical analyses, the formal numerical analysis cannot be reconstructed from the ClinicalTrials.gov record. The following describes how the registered endpoint would typically be handled statistically, without attributing these methods to the MIST registry.
| Analytic component | Typical approach for this endpoint | Status in reported MIST data |
|---|---|---|
| Outcome | Number of qualifying exacerbations | Registered |
| Exposure | Years of follow-up | Registered |
| Primary comparison | Comparison of exacerbation rates between randomized groups | Formal statistical analysis not reported |
| Count model | Poisson or another appropriate count-rate model | Not in the posted results |
| Overdispersion | Consider a negative-binomial framework when appropriate | Not in the posted results |
| Effect estimate | Rate ratio or another prespecified rate-based contrast | No estimate reported |
| Uncertainty | Confidence interval for the treatment effect | No confidence interval reported |
| Hypothesis test | Prespecified test of the treatment-rate contrast | No p-value reported |
11. Randomization and Blinding
MIST is registered as a randomized, parallel, quadruple-masked phase 3 trial. These design features are statistically important because they address different sources of bias.
Randomization
Random allocation helps balance known and unknown prognostic factors across treatment groups in expectation, supporting causal interpretation of between-group comparisons.
Parallel design
Participants are assigned to a treatment strategy and followed within that randomized group rather than serving sequentially as their own treatment comparison.
Quadruple masking
The registry identifies the study as quadruple-masked. Masking can reduce the influence of treatment knowledge on participant behavior, clinical management, outcome assessment, and other study processes.
Treatment purpose
The registry classifies the primary purpose as treatment, indicating that the trial was designed to evaluate treatment strategies rather than primarily diagnostic or observational questions.
12. Multiplicity, Interim Analysis, and Other Design Features
The ClinicalTrials.gov record does not provide statistical-analysis entries describing multiplicity adjustment, interim efficacy monitoring, alpha spending, Bayesian methods, non-inferiority margins, crossover, stratification factors, or missing-data/imputation procedures.
| Design topic | What the ClinicalTrials.gov record supports |
|---|---|
| Multiplicity | Not reported in the ClinicalTrials.gov record. |
| Interim analysis | Not reported in the ClinicalTrials.gov record. |
| Alpha spending | Not reported in the ClinicalTrials.gov record. |
| Bayesian methods | Not reported in the ClinicalTrials.gov record. |
| Non-inferiority margin | Not applicable from the ClinicalTrials.gov record; no non-inferiority design is identified. |
| Crossover | Not reported in the ClinicalTrials.gov record. |
| Stratification | Not reported in the ClinicalTrials.gov record. |
| Missing-data/imputation method | Not reported in the ClinicalTrials.gov record. |
This distinction is important for statistical interpretation. A method should not be inferred merely because it is common in similar clinical trials. The absence of an entry in the ClinicalTrials.gov record means that the method cannot be attributed to this trial from the source provided for this page.
13. Understanding the Primary Endpoint Without a Reported Effect Estimate
The registered endpoint measures the number of exacerbations per years of follow-up. It is therefore not identical to the probability that a child experiences at least one exacerbation during the study.
Raw event counts do not account for observation time. The registered endpoint explicitly uses years of follow-up, making the rate rather than the raw count the relevant measure.
A p-value, if reported, would address statistical evidence against a null hypothesis. It would not tell the reader whether the difference in exacerbation rates was small or large. The effect estimate and confidence interval are needed for that purpose.
A confidence interval around a rate ratio would describe uncertainty in the estimated population-level treatment contrast under the chosen model. It would not describe the range of exacerbation experiences that individual children could have.
14. Safety and Efficacy Are Different Questions
The MIST ClinicalTrials.gov record illustrate why safety and efficacy should be presented separately. The primary endpoint concerns exacerbations requiring systemic corticosteroids, while the available safety information concerns serious adverse events.
| Domain | Outcome in the ClinicalTrials.gov record | Statistical role |
|---|---|---|
| Efficacy | Rate of exacerbations requiring systemic corticosteroids | Registered primary endpoint |
| Safety | Serious adverse events by arm | Safety outcome |
A statistical comparison of efficacy does not automatically establish the safety profile, just as a safety event count does not measure the treatment effect on the primary efficacy endpoint. Each outcome requires its own definition, denominator, estimator, and uncertainty assessment.
15. Limitations
- Incomplete statistical-analysis detail: the ClinicalTrials.gov record contains no formal statistical analyses, so the formal primary analysis cannot be identified from the provided record.
- No numerical primary treatment effect reported: although results are posted, the ClinicalTrials.gov record contains no exacerbation-rate estimates, rate ratio, rate difference, confidence interval, or p-value.
- No analysis population reported: the ClinicalTrials.gov record does not specify whether the primary result was analyzed by intention-to-treat, per-protocol, or another population.
- No missing-data method reported: the ClinicalTrials.gov record does not identify how incomplete follow-up or other missing information was handled.
- No multiplicity strategy reported: 11 outcome measures are posted, but the ClinicalTrials.gov record does not describe a multiplicity adjustment or endpoint hierarchy.
- Generalizability: the registry itself cautions that the findings may not be applicable to young children whose asthma is more severe than that of the children in the study.
- Transient or infrequent wheezing: the registry also cautions that daily or intermittent use of inhaled glucocorticoids may not be efficacious in preschool-age children with transient or infrequent wheezing.
- Arm-label mapping: the ClinicalTrials.gov record uses Daily Budesonide and Intermittent Budesonide labels, while the intervention fields identify Budesonide and Placebo Budesonide. The ClinicalTrials.gov record does not provide enough detail to reconstruct every treatment component or dosing schedule.
16. Why This Trial Matters Statistically
MIST is a useful teaching example because its primary endpoint illustrates an important distinction in clinical-trial statistics: repeated event counts are not the same as binary outcomes. The trial also combines randomized allocation, parallel treatment groups, quadruple masking, a defined follow-up period, and a rate-based primary endpoint.
| Concept | How it appears in MIST |
|---|---|
| Randomization | The trial is registered as randomized. |
| Parallel design | The design model is registered as parallel. |
| Blinding | The registry identifies quadruple masking. |
| Count outcome | The primary endpoint counts exacerbations requiring prednisone. |
| Rate outcome | The count is divided by years of follow-up. |
| Repeated events | The rate formulation can retain information from multiple qualifying exacerbations. |
| Exposure time | Years of follow-up form the denominator of the registered endpoint. |
| Count regression | Poisson or negative-binomial approaches are typical frameworks for this type of endpoint, although the actual MIST model is not reported. |
| Effect estimation | A rate ratio or related contrast would provide magnitude; no numerical estimate is reported here. |
| Uncertainty | A confidence interval would quantify precision; none is reported in the ClinicalTrials.gov record. |
The trial therefore provides a particularly useful framework for learning why the choice of endpoint determines the appropriate statistical model. Treating a rate as though it were simply a binary proportion can discard information about event frequency and observation time.
17. Related Statistical Learning Pathway
Learn more about the methods used in this trial:
18. Related Statistical Calculators
19. Sources
- ClinicalTrials.gov: MIST, NCT00675584.
- Linked publication: PubMed record for PMID 22111718.
Continue through Clinical Biostats
Build from trial design and endpoint definitions into the statistical methods used to analyze clinical-trial data.
20. Record Summary
MIST is a randomized, parallel, quadruple-masked phase 3 trial with 278 enrolled participants and a registered primary endpoint measuring the rate of exacerbations requiring systemic corticosteroids during the 12-month follow-up period. The endpoint is defined as the number of exacerbations requiring prednisone per years of follow-up, making it a count/rate outcome rather than a simple binary event measure.
The ClinicalTrials.gov record indicates that results have been posted, but they contain no formal statistical analyses. Consequently, this page does not assign an effect estimate, confidence interval, or p-value to the primary endpoint. Instead, it explains the statistical framework appropriate for interpreting such an endpoint and distinguishes those general methods from analyses actually documented in the ClinicalTrials.gov record.
The available safety information reports serious adverse events of 7/139 for Daily Budesonide and 10/139 for Intermittent Budesonide. The registry also provides important generalizability caveats concerning children with more severe asthma and preschool-age children with transient or infrequent wheezing.